www.cems.riken.jp
Center for Emergent Matter Science2 0 2 3

Center for Emergent Matter Science
2-1 Hirosawa, Wako, Saitama 351-0198 Japan
Email: cems@riken.jp

RIKEN
RIKEN 2023-008

RIKEN

Center for Emergent Matter Science

Building a sustainablewithsociety that can co-exist in harmony
the environment

Message From the Director
The RIKEN Center for Emergent Matter
Science (CEMS) has been launched in
RIKEN unifying the fundamentals ofphysics, chemistry, and electronics, andrallying top-notch leaders as well as
up-and-coming young researchers.
In emergent matter science, we aim atrealizing emergent phenomena andfunctions by manipulating the dynamics
of electrons, spins, and molecules inmaterials, and creating materials anddevices for this purpose. Here the word
“emergence” means that qualitatively
new physical properties emerge inaggregates of many degrees of freedom,which cannot be expected in simple
assemblies of individual elements. The
three major-ﬁelds of CEMS are: (i)“Strong correlation physics”, exploring
the astonishing functions of materials
with many strongly-entangled electrons;(ii) Supramolecular/materials chemistry
designing the superstructures of molecules
for novel functions; and (iii) Quantum
information electronics utilizing thequantum entangled states as statevariables.

The mission of RIKEN centers is to solve
challenging and difﬁcult problems, which
requires gathering the individual abilities
of experts. The challenging goal of CEMS
is to explore the energy functions ofelectrons in solids and molecules leading
to the “third energy revolution”.
It is only about 120 years ago whenhumans acquired the infrastructure foraccessing electric energy and its transportsystem. If the ﬁrst and second energy
revolutions are deﬁned by the discoveries of burning energy from fuel and nuclear
reactions, respectively, by transforming
the mechanical energy from steam engines
to electric energy, the “third energy
revolution” should be the construction of
emergent electro-magnetism utilizing theelectron motions in solids and molecules,
which is beginning now. Namely, innovative research based on electrons insolids and molecules are now going on
at an accelerated pace, following theinnovations of semiconductor electronics, solar cells, and high-temperature
superconductivity.

CEMS aims at the discoveries of newprinciples/materials which bring about
the discontinuous leap of the ﬁgure of
merits, which can be attained only by
fundamental research on materials science.
The value of our research activities will be
judged based on how much we transmit
the new basic principles toward this goal.

Yoshinori Tokura
Director of Center for Emergent Matter Science

3

RIKEN Center for Emergent Matter Science
The Center for Emergent Matter Science (CEMS) brings together leading
scientists in three areas—physics, chemistry, and electronics—to elaborate theprinciples of emergent phenomena and to open the path to potential
applications.
CEMS carries out research in three areas: strongly-correlated materials,
supramolecular functional chemistry, and quantum information electronics. It
incorporates about 200 researchers from around the world, organized into
about 40 research groups and teams.
There are other leading centers around the world working in each of the threeareas covered by CEMS, but nowhere in the world is there a center that brings
the three together in one place. In order to create a sustainable society that can
co-exist with the natural environment, cooperation between the ﬁelds ofphysics, chemistry, and electronics is critical.
Bringing these three areas together allows “emergent phenomena” to takeplace within the center’ s research as well, making possible breakthroughs in
research that could not be predicted from the outset.
The goal of CEMS is not to develop technologies that can be immediately put
into application. It is not to push existing technologies forward, but rather topursue radical new technological principles that will contribute to humansociety in ﬁve decades or even a century in the future. To do this, it focuses onbasic research and the development of new theories.
Researchers who have pioneered these three ﬁelds have been brought
together along with young scientists who are not held back by existing
theories, to work as a team to take on this truly challenging research. This is
the real work of CEMS.

Introduction to EMS“Emergence” refers to the phenomenon in which a number of elements that are brought
together gain properties that could not be predicted from the individual elements. For
example, when a large number of electrons become strongly correlated, they can giverise to extremely strong electrical and magnetic action that could not be predicted fromthe actions of a single electron.
Additionally, by linking together a large number of molecules, it is possible to creatematerials with new functionalities that were not possessed by the individual molecules.
In this way, when particles such as electrons or molecules gather together, they cangive rise to surprising materials and functions that could not be predicted simply as anaggregation of the original constituent elements.
The science that attempts to elucidate the principles of emergent phenomena andcreate new materials and functions based on these principles is known as emergent
matter science. For example, the phenomenon of superconductivity, where metals andother compounds suddenly lose all their electrical resistance when cooled to a certain
degree, is a phenomenon that arises from the mutual interactions between electrons.
Normally, superconductivity appears at very low temperatures, but if we are able todesign and develop materials that are high-temperature superconductors, it will
become possible to transmit electricity without any loss.
In that way, emergent matter science has the potential to trigger a major revolution in
our lifestyles, and contribute to the achievement of a sustainable society that can
co-exist in harmony with the environment.

4

■ Strong Correlation Physics Division
Strong Correlation Physics Research Group (Yoshinori Tokura) ........... 6
Strong Correlation Theory Research Group (Naoto Nagaosa) ............... 7
Strong Correlation Interface Research Group (Masashi Kawasaki) ...... 8
Strong Correlation Quantum Structure Research Group (Takahisa Arima) .. 9Strong Correlation Materials Research Group (Yasujiro Taguchi) ....... 10
Strong Correlation Quantum Transport Research Team (Yoshinori Tokura) ... 11
Emergent Phenomena Measurement Research Team (Tetsuo Hanaguri) ..... 12
Quantum Matter Theory Research Team (Akira Furusaki) ................... 13
Computational Quantum Matter Research Team (Seiji Yunoki) .......... 14
First-Principles Materials Science Research Team (Ryotaro Arita) ..... 15
Electronic States Spectroscopy Research Team (Kyoko Ishizaka) ..... 16
Strongly Correlated Spin Research Team (Hazuki Furukawa) ............. 17
Electronic States Microscopy Research Team (Xiuzhen Yu) ............... 18
Emergent Photodynamics Research Team (Naoki Ogawa) ................. 19
Dynamic Emergent Phenomena Research Team (Fumitaka Kagawa) 20■ Supramolecular Chemistry Division
Emergent Soft Matter Function Research Group (Takuzo Aida) .......... 21
Emergent Molecular Function Research Team (Kazuo Takimiya) ........ 22
Emergent Bioinspired Soft Matter Research Team (Yasuhiro Ishida) .. 23
Emergent Device Research Team (Yoshihiro Iwasa) ............................ 24
Emergent Soft System Research Team (Takao Someya) ..................... 25
Emergent Functional Polymers Research Team (Keisuke Tajima) ....... 26
Emergent Bioengineering Materials Research Team (Yoshihiro Ito) .... 27
Emergent Supramolecular Materials Research Team (Yong-Jin Pu).... 28
Physicochemical Soft Matter Research Team (Fumito Araoka) ........... 29
Materials Characterization Support Team (Daisuke Hashizume)......... 30■ Quantum Information Electronics Division
Quantum Functional System Research Group (Seigo Tarucha) ........... 31
Quantum Condensate Research Team (Masahito Ueda) ...................... 32
Emergent Phenomena Observation Technology Research Team (Daisuke Shindo) .. 33
Quantum Nano-Scale Magnetism Research Team (Yoshichika Otani).. 34
Quantum System Theory Research Team (Daniel Loss) ....................... 35
Spin Physics Theory Research Team (Gen Tatara) ............................... 36
Quantum Effect Device Research Team (Koji Ishibashi) ....................... 37
Quantum Electron Device Research Team (Michihisa Yamamoto) ...... 38
Semiconductor Science Research Support Team (Fumihiro Matsukura) 39■ Cross-Divisional Materials Research Program
Emergent Molecular Assembly Research Unit (Hiroshi Sato) .............. 40
Computational Materials Function Research Unit (Yong Xu) ............... 41
Low-Dimensional Transport Research Unit (Ding Zhang) .................... 42
Topological Quantum Phenomenon Research Unit (Tian Liang) ......... 43
Emergent Spectroscopy Research Unit (Youtarou Takahashi) ............ 44
Emergent Functional Interface Research Unit (Masaki Nakano) ......... 45
Topological Quantum Matter Research Unit (Max Hirschberger) ........ 46
Topological Materials Design Research Unit (Motoaki Hirayama) ....... 47

Office of the Center Director
5Strong Correlation Physics Division

Strong Correlation Physics Research Group
Yoshinori Tokura (D.Eng.), Group Director
tokura@riken.jp
Research ﬁeld
Physics, Engineering, Materials Science

Keywords
Strongly correlated electron system, Topologicalinsulators, Spin-orbit interaction, Berry phase physics,
Multiferroics, Skyrmion

Brief resume
1981 D. Eng., University of Tokyo
1986 Associate Professor, University of Tokyo

Topological spin textures andemergent electromagnetic functions
Nanometric spin texture called "skyrmion". The skyrmion is the idea coined by Tony
Skyrme, a nuclear physicist, to describe a state of nucleon as the topological soliton. It
has recently been demonstrated that such a kind of topological particle should exist
widely in ubiquitous magnetic solids. The arrows in the ﬁgure represent the directions of
the spin (electron's magnetic moment); the spins direct up at the peripheral, swirl in going

1995 Professor, Department of Applied Physics, University ofTokyo
2001 Director, Correlated Electron Research Center, AIST2007 Group Director, Cross-Correlated Materials ResearchGroup, RIKEN
2008 AIST Fellow, National Institute of Advanced Industrial
Science and Technology (-present)2010 Director, Emergent Materials Department, RIKEN
2010 Group Director, Correlated Electron Research Group,
RIKEN

to the inside, and direct down at the core. This topology cannot be reached via

2013 Director, RIKEN Center for Emergent Matter Science(CEMS) (-present)

continuous deformation from the conventional spin orders, meaning that the skyrmion

2013 Group Director, Strong Correlation Physics ResearchGroup, Strong Correlation Physics Division, RIKEN
CEMS (-present)

can be viewed by a topologically protected particle. The skyrmion can carry a ﬁctitious(emergent) magnetic ﬁeld working on moving conduction electrons (represented by yellow
balls), and hence causes the topological Hall effect (transverse drift of the current).

2014 Team Leader, Strong Correlation Quantum Transport
Research Team, RIKEN CEMS (-present)

Furthermore, the electric current itself can drive the skyrmion. The critical current density

2017 Distinguished University Professor, University of Tokyo(-present)

for the drive of skyrmions is around 100 A/cm2, by ﬁve orders of magnitude smaller than

2019 Special University Professor, University of Tokyo

the conventional value for the drive of magnetic domain walls. These features may favor
the application of skyrmions to innovative spintronics, i.e. toward "skyrmionics".

Skyrmion and conduction electron motion

Publications
1. T. Hori, N. Kanazawa, M. Hirayama, K. Fujiwara, A. Tsukazaki, M. Ichikawa, M. Kawasaki, and Y. Tokura,“A Noble-Metal-Free Spintronic System with Proximity-Enhanced Ferromagnetic Topological Surface Stateof FeSi above Room Temperature”, Adv. Mater., 2206801 (2022).
2. A. Kitaori, N. Kanazawa, T. Yokouchi, F. Kagawa, N. Nagaosa, and Y. Tokura, “Emergent electromagnetic
induction beyond room temperature”, Proc. Natl. Acad. Sci. U.S.A. 118, e2105422118 (2021).
3. Y. Fujishiro, N. Kanazawa, R. Kurihara, H. Ishizuka, T. Hori, F. S. Yasin, X.Z. Yu, A. Tsukazaki, M. Ichikawa,M. Kawasaki, N. Nagaosa, M. Tokunaga, and Y. Tokura, “Giant anomalous Hall effect from spin-chirality
scattering in a chiral magnet”, Nat. Commun., 12, 317 (2021).
4. T. Yokouchi, F. Kagawa, M. Hirschberger, Y. Otani, N. Nagaosa, and Y. Tokura, “Emergent electromagnetic
induction in a helical-spin magnet”, Nature, 586, 232 (2020).
5. T. Kurumaji, T. Nakajima, M. Hirschberger, A. Kikkawa, Y. Yamasaki, H. Sagayama, H. Nakao, Y. Taguchi,
T. Arima, Y. Tokura, “Skyrmion lattice with a giant topological Hall effect in a frustrated triangular-latticemagnet”, Science, 365, 914 (2019).

6

1994 Professor, Department of Physics, University of Tokyo

OutlineOur group investigates a variety of emergent
phenomena in strongly correlated electron systems,
which cannot be understood within the framework of
conventional semiconductor/metal physics, toconstruct a new scheme of science and technology.
In particular, we focus on transport, dielectric andoptical properties in non-trivial spin/orbital structures,
aiming at clarifying the correlation between the
response and the spin/orbital state. In addition, weinvestigate electron systems with strong relativistic
spin-orbit interaction, unraveling its impact ontransport phenomena and other electronic properties.
Target materials include high-temperature
superconductors, colossal magnetoresistancesystems, multiferroics, topological insulators, andskyrmion materials.

Core members(Special Postdoctoral Researcher)
Yukako Fujishiro, Hinako Murayama(Senior Technical Scientist) Chieko Terakura

Strong Correlation Theory Research Group
Naoto Nagaosa (D.Sci.), Group Director
nagaosa@riken.jp
Research ﬁeld
Physics, Engineering, Materials Sciences

Keywords
Emergent electromagnetism, Magnetoelectric effect,
Shift current, Non-reciprocal effect, Spin Hall effect,
Interface electrons, Superconductivity

Brief resume
1983 Research Associate, University of Tokyo
1986 D.Sci., University of Tokyo

Shift current by phonon excitationin ferroelectrics
The shift current induced under light irradiation in crystals without inversion symmetry is
a current due to quantum geometry, which is essentially different from the normaltransport current. Therefore, it may be possible to induce a direct current without
generating photocarriers. Speciﬁcally, there is a process in which real excitation ofphonons occurs by light irradiation in an energy region lower than the bandgap and, atthe same time, direct current is generated through virtual electron-hole pairs. Thispossibility is expected to be applied to photodetectors in the terahertz region, and is
extremely interesting from the viewpoint of fundamental physics. Using the Feynman

1998 Professor, University of Tokyo (-present)
2001 Team Leader, Theory Team, Correlated Electron
Research Center, National Institute of Advanced
Industrial Science and Technology
2007 Team Leader, Theoretical Design Team, RIKEN
2010 Team Leader, Strong-Correlation Theory Research
Team, RIKEN
2013 Deputy Director, RIKEN Center for Emergent Matter
Science (CEMS) (-present)2013 Group Director, Strong Correlation Theory ResearchGroup, Division Director, Strong Correlation Physics
Division, RIKEN CEMS (-present)

Outlinediagram method, we formulated the nonlinear optical conductivity that expresses thisprocess, and based on the derived formula, we performed model calculations andﬁrst-principles band calculations. As a result, it is found that the shift current iscomparable between the actual interband transition with photon energy of eV order andthe phonon excitation with photon energy of about 10 meV order. These theoretical
calculations were compared with experimental observations and semi-quantitative
agreement was obtained. In particular, the DC current is almost independent of theexternal bias voltage, indicating no photocarrier generation.

(Left) Feynman diagram of the shift current due to phonons. (Right) Nonlinear optical response
function by ﬁrst-principles calculation. A is for the low-energy region corresponding to phonon
excitation, and B is for the visible-light region corresponding to electronic excitation.
Y. Okamura et al., “Photovoltaic effect by soft phonon excitation”, Proc. Nat. Acad. Sci.,119(14),e2122313119 (2022). https://doi.org/10.1073/pnas.2122313119

Publications
1. J. Ahn, G.Y. Guo, N.Nagaosa, A. Vishwanath, A “Riemannian geometry of resonant optical responses”,
Nat. Phys. 18, 290 (2022).
2. H. Ishizuka and N.Nagaosa, “Theory of bulk photovoltaic effect in Anderson insulator ”, Proc. Nat. Acad.
Sci., 118(10) e2023642118 (2021).
3. N. Nagaosa, “Emergent inductor by spiral magnets”, JJAP 58, 12909 (2019).
4. T. Morimoto, M. Nakamura, M. Kawasaki, and N. Nagaosa, "Current-Voltage Characteristic and Shot
Noise of Shift Current Photovoltaics", Phys. Rev. Lett., 121, 267401(2018).

We study theoretically the electronic states in solids
from the viewpoint of topology and explore newfunctions with non-dissipative currents. Combiningﬁrst-principles calculations, quantum ﬁeld theory, andnumerical analysis, we predict and design magnetic,
optical, transport and thermal properties of correlated
electrons focusing on their internal degrees of freedom
such as spin and orbital. In particular, we study
extensively the nontrivial interplay between thesevarious properties, i.e., cross-correlation, and develop
new concepts such as electron fractionalization andnon-dissipative quantum operation by considering the
topology given by the relativistic spin-orbit interaction
and/or spin textures.

Core members(Senior Research Scientist)
Andrey Mishchenko, Wataru Koshibae(Special Postdoctoral Researcher)
Xiao-Xiao Zhang, Yizhou Liu, Yoshihiro Michishita(Postdoctoral Researcher) Taekoo Oh

5. R. Wakatsuki, Y. Saito, S. Hoshino, Y. M. Itahashi, T. Ideue, M. Ezawa, Y. Iwasa, and N. Nagaosa,“Nonreciprocal charge transport in noncentrosymmetric superconductors”, Sci. Adv., 3, e1602390 (2017).
6. T. Morimoto, and N. Nagaosa, “Topological nature of nonlinear optical effects in solids”, Sci. Adv., 2,
e1501524 (2016).

7

Strong Correlation Physics Division

Strong Correlation Interface Research Group
Masashi Kawasaki (D.Eng.), Group Directorm.kawasaki@riken.jp
Research ﬁeld
Physics, Engineering, Chemistry, Materials Sciences

Keywords
Topological electronics, Thin ﬁlms and interfaces,
Topological materials, Unconventional photovoltaic
effect, Unconventional Hall effect

Brief resume
1989 D.Eng., University of Tokyo

Mott-insulator to metal transitionin artiﬁcial oxide quantum wells
It is widely known that many examples of unconventional superconductivity emerge
when carriers are doped in two dimensional Mott insulators. For many years, efforts havebeen focused on artiﬁcially fabricating two-dimensional Mott insulators with thin ﬁlm
technology of transition metal oxides. However, there have been few examples thatsucceeded in achieving metallic states by carrier doping.
In this study, we have employed a gas source molecular beam epitaxy system with our
original design. Conﬁned single quantum well structures are constructed by sandwichinga correlated metal SrVO3 layer with two band insulator SrTiO3 layers. High quality SVO3ﬁlms exhibit clearer transition from metal to insulator at about 1-2 nm when the thickness

1989 Postdoctoral Fellow, Japan Society for the Promotion of
Science1989 Postdoctoral Fellow, T. J. Watson Research Center, IBM,USA
1991 Research Associate, Tokyo Institute of Technology
1997 Associate Professor, Tokyo Institute of Technology
2001 Professor, Tohoku University
2007 Team Leader, Functional Superstructure Team, RIKEN
2010 Team Leader, Strong-Correlation Interfacial Device
Research Team, RIKEN
2011 Professor, University of Tokyo
2013 Deputy Director, RIKEN Center for Emergent Matter
Science (CEMS) (-present)2013 Group Director, Strong Correlation Interface ResearchGroup, Strong Correlation Physics Division, RIKEN
CEMS (-present)
2023 Research Strategy Advisor (Deputy Executive Director),
RIKEN (-present)is reduced. When electron carriers are doped in these quantum well Mott insulators,
metallic state is successfully induced. Thus, the SrVO3 quantum wells are demonstrated

Outlineas an ideal playground for studying physics of correlated electron systems.

Metal-insulator transition in SrVO3 two-dimensional artiﬁcial lattices

Publications
1. M. Nakamura, S. Inagaki, Y. Okamura, M. Ogino, Y. Takahashi, K. Adachi, D. Hashizume, Y. Tokura, and
M. Kawasaki “Band structures in orientation-controlled CuI thin ﬁlms under epitaxial strain”, Phys. Rev B.,
106, 125307 (2022).
2. M. Ohno, S. Minami, Y. Nakazawa, S. Sato, M. Kriener, R. Arita, M. Kawasaki, and M. Uchida “Maximizing
intrinsic anomalous Hall effect by controlling the Fermi level in simple Weyl semimetal ﬁlms”, Phys. Rev B.,
105, 125307 (2022).
3. K. S. Takahashi, Y. Tokura, and M. Kawasaki “Metal-insulator transitions in dimensionality controlled
LaxSr1-xVO3 ﬁlms”, APL Mater., 10, 111114 (2022).
4. R. Nishino, T. C. Fujita, and M. Kawasaki “Electric ﬁeld control of anomalous Hall effect in CaIrO3/CaMnO3
heterostructure”, APL Mater., 10, 081104 (2022).
5. J. Falson, I. Sodemann, B. Skinner, D. Tabrea, Y. Kozuka, A. Tsukazaki, M. Kawasaki, K. von Klitzing, andJ. H. Smet “Competing correlated states around the zero ﬁeld Wigner crystallization transition of electronsin two-dimensions”, Nat. Mater., 21, 311 (2022).

8

Thin ﬁlms and interfaces of topological materials are
the playground of our research. Chiral spin textures inreal space and magnetic monopoles in momentum
space are the sources of non-trivial Hall effect.
Photo-excited polar crystals generate unconventional
photocurrent. Not classical mechanics but quantum
mechanics is needed to understand those examples.
We will design and demonstrate possible devices thatutilize expectedly dissipationless electron ﬂow
exempliﬁed as above. The device physics study will
open a new avenue towards topological electronics
that manage ﬂow of information and energy carried bysuch topological current.

Core members(Senior Research Scientist)
Kei Takahashi, Masao Nakamura, Denis Maryenko(Junior Research Associate) Noriyuki Takahara

Strong Correlation Quantum Structure
Research Group
Taka-hisa Arima (Ph.D.), Group Director
takahisa.arima@riken.jp
Research ﬁeld
Materials Science, Physics

Keywords
X-ray scattering, Neutron scattering,Electron diffraction, Structure science, Imaging

Brief resume
1988 TORAY Co. Ltd.
1991 Research Associate, Faculty of Science, University ofTokyo

Spin-driven ferroelectricity andelectromagnon in multiferroic
Y-type hexaferrite compounds
Y-type hexaferrite compounds are composed of an alternate stacking of spinel block
layers and hexagonal perovskite block layers. The magnetic anisotropy of each layer andeffective exchange interaction are dependent on the composition. As a consequence,various magnetic orders appears in the temperature-magnetic ﬁeld plane. It is predictedthat two kinds of magnetic orders, transverse cone and double fan, can host electric1994 Ph.D. (Science), University of Tokyo
1995 Research Associate, Graduate School of Engineering,
University of Tokyo
1995 Associate Professor, Institute of Materials Science,
University of Tsukuba(2001-2006 Group Leader, ERATO Tokura Spin Super
Structure Project)
2004 Professor, Institute of Multidisciplinary Research for
Advanced Materials, Tohoku University
2011 Professor, Graduate School of Frontier Sciences,
University of Tokyo (-present)
2007 Team Leader, Spin Order Research Team, RIKEN
SPring-8 Center

measurements of magnetization, electric polarization, and spin-polarized neutron2013 Team Leader, Strong Correlation Quantum Structure
Research Team, RIKEN Center for Emergent Matter
Sciencescattering in BaSrCo2Fe11AlO22. It has been found that the alternate longitudinal cone ﬁrst

2023 Deputy Director, RIKEN Center for Emergent Matter
Science (CEMS) (-present)

polarization via the inverse Dzyalloshinsky-Moriya interaction. We performed

appears by cooling from a high temperature at zero magnetic ﬁeld. If a magnetic ﬁeld is
once applied perpendicular to the c-axis at low temperatures, the double fan replaces2023 Group Director, Strong Correlation Quantum Structure
Research Group, RIKEN Center for Emergent Matter
Science (-present)

and survives even after the magnetic ﬁeld is turned off. The electric polarization is also
induced along the axis perpendicular both to the

Outlinec-axis and to the magnetic ﬁeld. The electric
po l a r izatio n is rever s ed b y sw i t c hi ng t hemagnetic ﬁeld direction. Inelastic spin-polarized
neutron scattering has predicted that both the
double fan and alternative longitudinal cone may
host an electromagnon (magnon excited by THz
electric ﬁeld).

Magnetic-ﬁeld induced reversal of electric polarizationand possible change in magnetic structure in a Y-type
hexaferrite BaSrCo2Fe11AlO22.

Publications
Publications
1. V. Ukleev, O. Utesov, L. Yu, C. Luo, K. Chen, F. Radu, Y. Yamasaki, N. Kanazawa, Y. Tokura, T. Arima, J.
S. White, “Signature of anisotropic exchange interaction revealed by vector-ﬁeld control of the helical orderin a FeGe thin plate”, Phys. Rev. Research 3, 013094 (2021).
2. Y. Ishii, K. Yamamoto, Y. Yokoyama, M. Mizumaki, H. Nakao, T. Arima, Y. Yamasaki, “Soft-X-ray Vortex
Beam Detected by Inline Holography”, Phys. Rev. Appl. 14, 064069 (2020).
3. T. Nakajima, T. Oda, M. Hino, H. Endo, K. Ohishi, K. Kakurai, A. Kikkawa, Y. Taguchi, Y. Tokura, T. Arima,“Crystallization of magnetic skyrmions in MnSi investigated by neutron spin echo spectroscopy”, Phys.
Rev. Research 2, 043393 (2020).
4. V. Ukleev, Y. Yamasaki, O., Utesov, K. Shibata, N. Kanazawa, N. Jaouen, H. Nakao, Y. Tokura, T. Arima,“Metastable solitonic states in the strained itinerant helimagnet FeGe”, Phys. Rev. B 102, 014416 (2020).
5. S. Gao, M. Hirschberger, O. Zaharko, T. Nakajima, T. Kurumaji, A. Kikkawa, J. Shiogai, A. Tsukazaki, S.
Kimura, S. Awaji, Y. Taguchi, T. Arima, Y. Tokura, “Ordering phenomena of spin trimers accompanied by alarge geometrical Hall effect”, Phys. Rev. B 100, 241115(R) (2019).

Strongly correlated electron systems may exhibit
various interesting emergent phenomena such as
superconductivity, colossal magneto-resistance, andgiant magneto-electric effects. These emergent
phenomena are directly associated with the spatial
distributions as well as the spatial and temporal
ﬂuctuations of atoms, electron density, and spin
density. To reveal these phenomena, we perform
crystallographic and magnetic structure analyses,
spectroscopies, and microscopies by usingsynchrotron x-rays, neutrons, and high-energy
electron beams.

Core members(Special Postdoctoral Researcher) Masaki Gen(Postdoctoral Researcher) Kamini Gautam

9Strong Correlation Physics Division

Strong Correlation Materials Research Group
Yasujiro Taguchi (D.Eng.), Group Director
y-taguchi@riken.jp
Research ﬁeld
Physics, Engineering, Materials Science

Keywords
Strongly correlated electron system, Skyrmion,
Multiferroics, Thermoelectric effect

Brief resume
1993 Researcher, SONY Corporation
1997 Research Associate, University of Tokyo

Discovery of new magnet hosting
antiskyrmions at room temperature
Skyrmion is a nanometric magnetic vortex characterized by an integer topologicalnumber, which behaves as a stable particle, and anticipated to be applied tohigh-performance magnetic memory devices. Recently, a new magnetic vortex,

2002 D.Eng., University of Tokyo
2002 Associate Professor, Institute for Materials Research,
Tohoku University
2007 Team Leader, Exploratory Materials Team, RIKEN
2010 Team Leader, Strong-Correlation Materials Research
Team, RIKEN
2013 Team Leader, Strong Correlation Materials Research
Team, Strong Correlation Physics Division, RIKEN
Center for Emergent Matter Scienceattention. However, antiskyrmions have thus far been observed only in Heusler

2018 Group Director, Strong Correlation Materials ResearchGroup, Strong Correlation Physics Division, RIKEN
Center for Emergent Matter Science (-present)

compounds with D 2d symmetry. This limitation has prevented intensive studies of2018 Director, Ofﬁce of the Center Director, RIKEN Center for
Emergent Matter Science (-present)

antiskyrmion, with the opposite sign of the topological number has attracted much

topological properties of antiskyrmions and their applications. Our group discovered a
Pd-doped Schreibersite, Fe1.9Ni0.9Pd0.2P, with S4 symmetry to host antiskyrmions over a

Outlinewide temperature range including room temperature. It was also found that antiskyrmionsand skyrmions are interconverted to each other by changing magnetic ﬁelds or sample
thickness. Furthermore, sawtooth-like novel magnetic domain patterns with S4 symmetry
were observed near the surface of thick crystals.

Schematics of (a) skyrmion, (b)antiskyrmion, and(c) symmetry of the crystal structures hosting antiskyrmions.

Publications
1. V. Kocsis, Y. Kaneko, Y. Tokunaga, Y. Tokura, and Y. Taguchi, “Enhanced stability of the multiferroic phasein Cr-doped Y-type hexaferrite single-crystals”, Phys. Rev. Appl., 18, 024050 (2022).
2. K. Karube, L. C. Peng, J. Masell, M. Hemmida, H.-A. Krug von Nidda, I. Kézsmárki, X. Z. Yu, Y. Tokura,
and Y. Taguchi, “Doping control of magnetic anisotropy for stable antiskyrmion formation in schreibersite(Fe,Ni)3P with S4 symmetry”, Adv. Mater., 34, 2108770 (2022).
3. K. Karube, L. C. Peng, J. Masell, X. Z. Yu, F. Kagawa, Y. Tokura, and Y. Taguchi, “Room-temperature
antiskyrmions and sawtooth surface textures in a non-centrosymmetric magnet with S4 symmetry”, Nat.
Mater., 20, 335 (2021).
4. M. Kriener, M. Sakano, M. Kamitani, M. S. Bahramy, R. Yukawa, K. Horiba, H. Kumigashira, K. Ishizaka, Y.
Tokura, and Y. Taguchi, “Evolution of Electronic States and Emergence of Superconductivity in the Polar
Semiconductor GeTe by Doping Valence-Skipping Indium”, Phys. Rev. Lett., 124, 047002 (2020).
5. V. Kocsis, T. Nakajima, M. Matsuda, A. Kikkawa, Y. Kaneko, J. Takashima, K. Kakurai, T. Arima, F. Kagawa,Y. Tokunaga, Y. Tokura, and Y. Taguchi, “Magnetization-polarization cross-control near room temperaturein hexaferrite single crystals”, Nat. Commun., 10, 1247 (2019).

10

Our group aims at obtaining gigantic cross-correlation
responses, understanding their mechanisms, anddeveloping new functions in strongly-correlated-electron bulk materials, such as transition-metal oxides. To
this end, we try to synthesize a wide range of materials using various methods, including high-pressuretechniques, and investigate their physical properties.
Speciﬁc targets are: (1) exploration of new skyrmion
materials; (2) obtaining gigantic magnetoelectric
responses in mutiferroic materials at high temperatures; (3) exploration of new magnetic materials; (4)exploration of new thermoelectric materials.

Core members(Senior Research Scientist)
Markus Kriener, Kosuke Karube(Research Scientist) Daisuke Nakamura(Senior Technical Scientist) Akiko Kikkawa

Strong Correlation Quantum Transport
Research Team
Yoshinori Tokura (D.Eng.), Team Leader
tokura@riken.jp
Research ﬁeld
Physics, Engineering, Materials Science

Keywords
Strongly correlated electron system, High-temperature
superconductor, Spin-orbit interaction, Topologicalinsulators, Interface electronic structure

Brief resume
1981 D. Eng., University of Tokyo
1986 Associate Professor, University of Tokyo

Quantum transport phenomena ofsurface Dirac states inthin ﬁlm superstructures
The topological insulator is a new state of matter, whose bulk is a three-dimensional

1994 Professor, Department of Physics, University of Tokyo
1995 Professor, Department of Applied Physics, University ofTokyo
2001 Director, Correlated Electron Research Center, AIST2007 Group Director, Cross-Correlated Materials ResearchGroup, RIKEN
2008 AIST Fellow, National Institute of Advanced Industrial
Science and Technology (-present)

charge-gapped insulator but whose surface hosts a two-dimensional Dirac electron state.

2010 Director, Emergent Materials Department, RIKEN

Surface Dirac states are characterized by massless electrons and holes whose spins are2010 Group Director, Correlated Electron Research Group,
RIKEN

polarized perpendicular to their crystal momentum. As a result, the quantum transportphenomena stemming from their charge and spin degrees of freedom are promising forthe applications to low-power consumption electronic devices. The well-known example
for this is the quantum anomalous Hall effect (QAHE) in which one-dimensional

2013 Director, RIKEN Center for Emergent Matter Science(CEMS) (-present)2013 Group Director, Strong Correlation Physics ResearchGroup, Strong Correlation Physics Division, RIKEN
CEMS (-present)

conducting channel without any dissipation emerges at zero magnetic ﬁeld. We

2014 Team Leader, Strong Correlation Quantum Transport
Research Team, RIKEN CEMS (-present)

established the growth of high quality thin ﬁlm superstructure of topological insulator

2017 Distinguished University Professor, University of Tokyo(-present)(BixSb1-x)2Te3 sandwiched by ferromagnetic insulator (Zn,Cr)Te, by means of molecular2019 Special University Professor, University of Tokyo

beam epitaxy (MBE) method. We cooled down to cryogenic temperature, andsuccessfully observed QAHE. We will make full use of the thin ﬁlm superstructure to add

Outlinefunctionality to topological materials. In particular, we now embark on the observation orcontrol of the Majorana quasiparticle, which is expected to be applied to quantum
computers.

Schematic of the quantum Hall effect on the surface of a topological insulator

Publications
1. M. Kawamura, M. Mogi, R. Yoshimi, T. Morimoto, K. S. Takahashi, A. Tsukazaki, N. Nagaosa, M. Kawasaki,
and Y. Tokura, "Laughlin charge pumping in a quantum anomalous Hall insulator", Nat. Phys. (2023).
2. M. Mogi, Y. Okamura, M. Kawamura, R. Yoshimi, K. Yasuda, A. Tsukazaki, K. S. Takahashi, T. Morimoto,
N. Nagaosa, M. Kawasaki, Y. Takahashi, and Y. Tokura, “Experimental signature of the parity anomaly in asemi-magnetic topological insulator”, Nat. Phys.,18, 390 (2022).
3. K. Yasuda, T. Morimoto, R. Yoshimi, M. Mogi, A. Tsukazaki, M. Kawamura, K. S. Takahashi, M. Kawasaki,
N. Nagaosa and Y. Tokura, “Large non-reciprocal charge transport mediated by quantum anomalous Halledge states”, Nat. Nanotechnol., 15, 831 (2020).
4. K. Yasuda, H. Yasuda, T. Liang, R. Yoshimi, A. Tsukazaki, K. S. Takahashi, N. Nagaosa, M. Kawasaki, andY. Tokura, “Nonreciprocal charge transport at topological insulator/superconductor interface”, Nat.
Commun., 10, 2734 (2019).
5. R. Yoshimi, K. Yasuda, A. Tsukazaki, K. S. Takahashi, M. Kawasaki, and Y. Tokura, “Current-driven
magnetization switching in ferromagnetic bulk Rashba semiconductor (Ge, Mn) Te”, Sci. Adv., 4, eaat9989(2018).

We study various kinds of quantum transportphenomena which emerge in bulk materials and athetero-interfaces of thin ﬁlms, focusing on electron
systems with strong correlation and/or strong
spin-orbit interactions. Speciﬁcally, we try to clarify
quantum states of Dirac electrons at surface/interfacesof topological insulators as well as in bulk Rashba
system with broken inversion symmetry, by observing
Landau level formation, quantum (anomalous) Hall
effect, and various quantum oscillation phenomena at
low temperatures and in high magnetic ﬁelds. Also, we
synthesize high-temperature superconducting
cuprates in bulk forms and various transition-metaloxides thin ﬁlms, and measure transport properties
under high pressure or high magnetic-ﬁeld, aiming at
increasing superconducting transition temperature andat ﬁnding novel magneto-transport properties.

Core members(Senior Research Scientist) Minoru Kawamura(Research Scientist) Ryutaro Yoshimi(Special Postdoctoral Researcher)
Ilya Belopolski, Yuki Sato, Max Birch

11

Strong Correlation Physics Division

Emergent Phenomena Measurement
Research Team
Tetsuo Hanaguri (D.Eng.), Team Leader
hanaguri@riken.jp
Research ﬁeld
Physics, Engineering, Materials Sciences

Keywords
Scanning tunneling microscopy, Superconductivity,
Topological insulators

Brief resume
1993 D.Eng., Tohoku University
1993 Research Associate, Department of Basic Science, The
University of Tokyo

Direct imaging of massless electrons
at the surface of a topological insulator
Topological insulators are a new phase of matter which was discovered recently.
Although it is an insulator in the bulk, a topological insulator possesses a metallic surface

1999 Associate Professor, Department of Advanced Materials
Science, The University of Tokyo
2004 Senior Research Scientist, Magnetic Materials
Laboratory, RIKEN
2013 Team Leader, Emergent Phenomena Measurement
Research Team, Strong Correlation Physics Division,
RIKEN Center for Emergent Matter Science (-present)

where electrons lose their mass. The surface state is expected to serve as a base of
spintronics application, because spins of massless electrons can be used to handle

Outlineinformation. However, the experimental understanding of massless electrons is still
elusive.
Using scanning tunneling microscope, our team succeeded in imaging the nano-scalespatial structure of massless electrons at the surface of a topological insulator Bi 2Se3. We
focus on imaging in a magnetic ﬁeld, where electrons exhibit cyclotron motion. The centerof the cyclotron motion drifts around the charged defect, resulting in an “electron ring”.
We found that the unique character of massless electrons manifests itself in the internal
structure of the electron ring. The observed internal structure is related to the spin
distribution and will give us an important clue for future spintronics applications.

”Electron rings” atdifferent energies

Publications
1. C. J. Butler, Y. Kohsaka, Y. Yamakawa, M. S. Bahramy, S. Onari, H. Kontani, T. Hanaguri, and S. Shamoto,“Correlation-driven electronic nematicity in the Dirac semimetal BaNiS2”, Proc. Natl. Acad. Sci. USA, 119,e2212730119 (2022).
2. T. Machida, Y. Nagai, and T. Hanaguri, “Zeeman effects on Yu-Shiba-Rusinov states”, Phys. Rev. Res., 4,033182 (2022).
3. T. Machida, Y. Yoshimura, T. Nakamura, Y. Kohsaka, T. Hanaguri, C.-R. Hsing, C.-M. Wei, Y. Hasegawa, S.
Hasegawa, and A. Takayama, “Superconductivity near the saddle point in the two-dimensional Rashba
system Si(111)√3×√3-(Tl,Pb)”, Phys. Rev. B, 105, 064507 (2022).
4. S. Kasahara, H. Suzuki, T. Machida, Y. Sato, Y. Ukai, H. Murayama, S. Suetsugu, Y. Kasahara, T.
Shibauchi, T. Hanaguri, and Y. Matsuda, “Quasiparticle Nodal Plane in the Fulde-Ferrell-Larkin-Ovchinnikov
State of FeSe”, Phys. Rev. Lett., 127, 257001 (2021).
5. C. J. Butler, M. Yoshida, T. Hanaguri, and Y. Iwasa, “Doublonlike Excitations and Their Phononic Coupling
in a Mott Charge-Density-Wave System”, Phys. Rev. X, 11, 011059 (2021).

12

We experimentally study electronic states related toemergent phenomena in electron systems, such as
high-temperature superconductivity and topologicalquantum phenomena. For this purpose, we use
scanning tunneling microscopes working under
combined extreme conditions of very low
temperatures, high magnetic ﬁelds and ultra-highvacuum. Modern scanning-tunneling-microscopy
technology enables us to obtain a “map of theelectronic state” with atomic-scale spatial resolution.
We make and analyze the maps of various materials
and establish the relationships between material
properties and electronic states. We also pursue thedevelopment of novel measurement techniques todiscover new emergent phenomena in condensed
matter.

Core members(Senior Research Scientist) Tadashi Machida(Research Scientist) Christopher John Butler(Special Postdoctoral Researcher) Masahiro Naritsuka

Quantum Matter Theory Research Team
Akira Furusaki (D.Sci.), Team Leader
furusaki@riken.jp
Research ﬁeld
Physics, Materials Science

Keywords
Electron correlation, Frustrated quantum magnets,
Topological insulators, Topological superconductivity

Brief resume
1991 Research Associate, Department of Applied Physics,
University of Tokyo
1993 Ph.D., University of Tokyo

Classifying topological insulators andtopological superconductors

1993 Postdoctoral Associate, Massachusetts Institute ofTechnology, USA
1995 Research Associate, Department of Applied Physics,
University of Tokyo

Modern electronics is based on the band theory that describes quantum mechanical

1996 Associate Professor, Yukawa Institute for Theoretical
Physics, Kyoto University

motion of electrons in a solid. The band theory can explain properties of metals, insulators

2003 Chief Scientist, Condensed Matter Theory Laboratory,
RIKEN (-present)

and semiconductors, and led to the invention of transistors. However, recent studies
revealed some important physics which was missed in the standard band theory. Namely,
the geometric (Berry) phase of electron wave functions can have a nontrivial topological2013 Team Leader, Quantum Matter Theory Research Team,
Strong Correlation Physics Division, RIKEN Center for
Emergent Matter Science (-present)

structure in momentum space, and this leads to a topological insulator. In addition,
superconductors with gapped quasiparticle excitations can be a topological

Outlinesuperconductor. In principle there are various types of topological insulators (TIs) andtopological superconductors (TSCs) in nature.
We constructed a general theory that can classify TIs and TSCs in terms of genericsymmetries. This theory shows that in every spatial dimension there are three types of
TIs/TSCs with an integer topological index and two types of TIs/TSCs with a binary
topological index. We extend our theory to understand the effect of crystalline symmetry
and electron correlation.

A coffee mug and a donut are equivalent in topology because they canbe continuously deformed from one to the other. The wave functions ofelectrons in insulators can be topologically lassiﬁed.

We investigate novel quantum phases of many-electron systems in solids which emerge as a result ofstrong electron correlation and quantum effects. We
theoretically study electronic properties of these newphases (such as transport and magnetism) and criticalphenomena at phase transitions. Speciﬁcally, we
study topological insulators and superconductors,
frustrated quantum magnets, and other strongly
correlated electron systems in transition metal oxides
and molecular conductors, etc. We construct effective models for electrons in these materials and unveil
their various emergent phases by solving quantum
statistical mechanics of these models using bothanalytical and numerical methods.

Publications
Core members
1. Y. Yao, M. Oshikawa, and A. Furusaki, “Gappability index for quantum many-body systems”, Phys. Rev.
Lett., 129, 017204 (2022).
2. S. Kobayashi and A. Furusaki, “Fragile topological insulators protected by rotation symmetry without
spin-orbit coupling”, Phys. Rev. B, 104, 195114 (2021).
3. S. Furukawa and T. Momoi, “Effects of Dzyaloshinskii-Moriya interactions in Volborthite: Magnetic orders
and thermal Hall effect”, J. Phys. Soc., 89, 034711 (2020).

(Senior Research Scientist)
Tsutomu Momoi, Shigeki Onoda, Hitoshi Seo(Research Scientist) Shingo Kobayashi(Postdoctoral Researcher) Ikuma Tateishi

4. M. Naka, S. Hayami, H. Kusunose, Y. Yanagi, Y. Motome, and H. Seo, “Spin current generation in organic
antiferromagnets”, Nat. Commun., 10, 4305 (2019).
5. S. Onoda and F. Ishii, “First-principles design of the spinel iridate Ir2O4 for high-temperature quantum spinice”, Phys. Rev. Lett., 122, 067201 (2019).

13

Strong Correlation Physics Division

Computational Quantum Matter Research Team
Seiji Yunoki (D.Eng.), Team Leader
yunoki@riken.jp
Research ﬁeld
Physics, Materials Science

Keywords
Strongly correlated electron system, Magnetism,
Superconductivity, Computational condensed matterphysics

Brief resume
1996 D.Eng., Nagoya University

Mechanism of novel insulating state andpossible superconductivity induced bya spin-orbit coupling
Electrons in solids are moving around, affected by the Coulomb interaction,
electron-lattice interaction, and spin-orbit interaction, which induces different behaviors
characteristic of each material. Recently, the study for the spin-orbit coupling has greatly
progressed and attracted much attention. In the 5d transition metal oxide Sr2 IrO4 , the spinand orbital degrees of freedom are strongly entangled due to the large spin-orbit coupling
and the novel quantum state is formed. Sr 2 IrO 4 is also expected to be a possiblesuperconducting material with a great deal of similarities to the parent compound ofcuprate high-temperature superconductivity.
We have studied the detailed electronic properties of a 3-orbital Hubbard model for Sr2
IrO4 with several computational methods. Our calculations have clearly shown that the
ground state of this material is an effective total angular momentum J eff=1/2
antiferromagnetic insulator, where Jeff is “pseudospin”,formed by spin and orbital degrees
of freedom due to the strong spin-orbit coupling (x-AFI in Fig. (a)). We have also proposed

1996 Postdoctoral Researcher, National High Magnetic Field
Laboratory, USA
1999 Postdoctoral Researcher, Materials Science Center,
Groningen University, Netherlands
2001 Postdoctoral Researcher, International School for
Advanced Studies, Italy
2006 Long-Term Researcher and Research AssistantProfessor, Oak Ridge National Laboratory and Universityof Tennessee, USA
2008 Associate Chief Scientist, Computational Condensed
Matter Physics Laboratory, RIKEN
2010 Team Leader, Computational Materials Science
Research Team, RIKEN Advance Institute for
Computational Science2013 Team Leader, Computational Quantum Matter Research
Team, RIKEN Center for Emergent Matter Science(-present)2017 Chief Scientist, Computational Condensed Matter
Physics Laboratory, RIKEN (-present)2018 Team Leader, Computational Materials Science
Research Team, RIKEN Center for Computational
Science (-present)
2021 Team Leader, Quantum Computational Science
Research Team, RIKEN Center for Quantum Computing(-present)

Outlinethat the dx2-y2 -wave “pseudospin singlet” superconductivity (SC in Fig. (b)) is induced byelectron doping into the Jeff=1/2 antiferromagnetic insulator Sr2IrO4.

Ground state phase diagram of 3-orbital Hubbard model with aspin-orbit coupling. (a) Electron density n=5, (b) n>5.

Publications
1. F. Lange, S. Ejima, J. Fujimoto, T. Shirakawa, H. Fehske, S. Yunoki, and S. Maekawa, “Generation ofcurrent vortex by spin current in Rashba systems”, Phys. Rev. Lett. 126, 157202 (2021).
2. H. Watanabe, T. Shirakawa, K. Seki, H. Sakakibara, T. Kotani, H. Ikeda, and S. Yunoki, “Uniﬁed descriptionof cuprate superconductors suing a four-band d-p model”, Phys. Rev. Research 3, 033157 (2021).
3. K. Seki and S. Yunoki, “Thermodynamic properties of an S=1/2 ring-exchange model on the triangularlattice”, Phys. Rev. B 101, 235115 (2020).
4. K. Seki and S. Yunoki, "Emergence of a thermal equilibrium in a subsystem of a pure ground state byquantum entanglement", Phys. Rev. Research 2, 043087 (2020).
5. T. Kaneko, T. Shirakawa, S. Sorella, and S. Yunoki, "Photoinduced eta pairing in the Hubbard model",Phys. Rev. Lett. 122, 077002 (2019).

14

Electrons in solids are in motion within the energy
band reﬂecting the lattice structure of each material.
The Coulomb interaction, electron-lattice interaction,and spin-orbit interaction have nontrivial effects on the
motion of electrons and induce various interesting
phenomena. Our aim is to elucidate the emergent
quantum phenomena induced by cooperation orcompetition of these interactions, usingstate-of-the-art computational methods for condensed
matter physics. Our current focus is on various
functional transition metal oxides, topologicalmaterials, and heterostructures made of thesematerials. Our research will lead not only to clarify themechanism of quantum phenomena in existentmaterials but also to propose novel materials.

Core members(Reseach Scientist) Kazuya Shinjo

First-Principles Materials Science Research Team
Ryotaro Arita (D.Sci.), Team Leader
arita@riken.jp
Research ﬁeld
Physics, Materials Science

Keywords
First-principles calculations, Theoretical materials
design, Strongly correlated electron systems

Brief resume
2000 D.Sci., University of Tokyo
2000 Research Associate, Department of Physics, Universityof Tokyo

Ab initio prediction of magnetic structures
In a magnetic material, some of the atoms in a crystal carry magnetic moments, whichalign themselves with their neighbors in very speciﬁc formations. The smallest building
block of a magnetic material -the magnetic structure- fundamentally determines the properties of a magnet. Yet the prediction is highly nontrivial due to the many degrees of freedom in the system. We formulated a scheme to predict the magnetic structure from ﬁrst
principles by combining the cluster multipole method and spin density functional theory,in which we start with a sophisticated list of possible spin conﬁgurations.
The list of conﬁgurations is found in a spherical expansion analogous to how atomic
orbitals are constructed, but highly adapted to the crystal symmetry. We then performed
a high-throughput calculation with close to 3,000 possible magnetic structures for 131

2004 Postdoctoral Researcher, Max Planck Institute for Solid
State Research
2006 Research Scientist/Senior Research Scientist,
Condensed Matter Theory Laboratory, RIKEN
2008 Associate Professor, Department of Applied Physics,
University of Tokyo
2011 PRESTO, Japan Science and Technology Agency
2014 Team Leader, First-Principles Materials Science
Research Team, RIKEN Center for Emergent Matter
Science (-present)2018 Professor, Department of Applied Physics, University ofTokyo
2022 Professor, Research Center for Advanced Science andTechnology, University of Tokyo (-present)

Outlinematerials and found many stable and meta-stable magnetic structures. We compared our
prediction to the reference standard, which we aim to reproduce, that is, the experiment.
This kind of high-throughput benchmark
calculation showed that our approach cansigniﬁcantly narrow down the possible properties of a material.
With this scheme, the exploration of magnetic materials is pushed to enter a newparadigm of material design that lives up to
the era of big data.

Scheme for magnetic structure prediction.

Publications
1. Y. Nomura, S. Sakai, and R. Arita, “Fermi surface expansion above critical temperature in a Hundferromagnet”, Phys. Rev. Lett., 128, 206401 (2022)
2. Y. Nomura, R. Arita, “Superconductivity in inﬁnite-layer nickelates”, Rep. Prog. Phys., 85 052501 (2022).
3. M.-T. Huebsch, T. Nomoto, M.-T. Suzuki, R.Arita, “Benchmark for Ab Initio Prediction of Magnetic
Structures Based on Cluster-Multipole Theory”, Phys. Rev. X 11, 011031 (2021).
4. T. Nomoto, T. Koretsune, R. Arita, “Formation Mechanism of the Helical Q Structure in Gd-Based
Skyrmion Materials”, Phys. Rev. Lett. 125, 117204 (2020).
5. J. A. Flores-Livas, L. Boeri, A. Sanna, G. Profeta, R. Arita, M. Eremets, “A perspective on conventional
high-temperature superconductors at high pressure: Methods and materials”, Phys. Rep. 856, 1-78
(2020).

By means of ﬁrst-principles methods, our team studies
non-trivial electronic properties of materials which leadto new ideas/notions in condensed matter physics or
those which have potential possibilities as uniquefunctional materials. Especially, we are currently
interested in strongly correlated/topological materials
such as high Tc cuprates, iron-based superconductors,organic superconductors, carbon-based
superconductors, 5d transition metal compounds,
heavy fermions, giant Rashba systems, topologicalinsulators, zeolites, and so on. We aim at predicting
unexpected phenomena originating from many-bodycorrelations and establishing new guiding principles formaterials design. We are also interested in thedevelopment of new methods for ab initio electronic
structure calculation.

Core members(Senior Research Scientist) Shiro Sakai(Research Scientist) Yusuke Nomura(Special Postdoctoral Researcher)
Hsiao-Yi Chen, Rikuto Oiwa, Jean B.P.G. Moree(International Program Associate) Ming-Chun Jiang

15

Strong Correlation Physics Division

Electronic State Spectroscopy Research TeamKyoko Ishizaka (Ph.D.), Team Leader
kyoko.ishizaka@riken.jp
Research ﬁeld
Physics, Materials Science

Keywords
Ultrafast time-resolved TEM, Photoelectron
Spectroscopy, Strongly Correlated Electron System,
Superconductivity, Topological Materials

Brief resume
2004 Ph.D., Engineering, University of Tokyo

Nano-to-micro spatiotemporal imaging ofmagnetic skyrmions
Magnetic skyrmions are self-organized topological spin textures that behave likeparticles. Because of their fast creation and typically long lifetime, experimental veriﬁcationof skyrmion’ s creation/annihilation processes has been challenging. Our teamsuccessfully tracked skyrmion dynamics in a room-temperature chiral magnet by using
pump-probe Lorentz transmission electron microscope. Following the nanosecond
photothermal excitation, we resolved 160-nm skyrmion’ s proliferation at <1 ns,

2004 Research Associate, Institute for Solid State Physics,
University of Tokyo
2010 Associate Professor, Department of Applied Physics,
School of Engineering, University of Tokyo
2014 Associate Professor, Quantum-Phase Electronics
Center, School of Engineering, University of Tokyo
2016 Team Leader, Electronic States Spectroscopy Research
Team, Strong Correlation Physics Division, RIKEN
Center for Emergent Matter Science (-present)2018 Professor, Quantum-Phase Electronics Center, School ofEngineering, University of Tokyo (-present)

Outlinecontraction at 5 ns, drift from 10 ns to 4 µs, and coalescence at ~5 µs. These motions
relay the multiscale arrangement and relaxation of skyrmion clusters in a repeatable cycle.
Such repeatable dynamics of skyrmions, arising from the weakened but still persistent
topological protection around defects, enables us to visualize the whole life of theskyrmions and demonstrates the possible high-frequency manipulations of topologicalcharges brought by skyrmions.

We investigate the electronic states of materials
showing a variety of physical properties, functions,and quantum phenomena. By utilizing spin- andangle-resolved photoemission spectroscopy, which
can probe the energy, momentum, and spin ofelectrons, we investigate new materials, topologicalquantum states, and many-body effects in strongly
correlated systems. We are also developing thepulsed-laser based ultrafast transmission electron
microscopy, aiming for probing the dynamical statesof nanoscale spin/lattice/charge textures, materials,
and devices.
Spatiotemporal imaging of magnetic skyrmions recorded by ultrafast Lorentz electron microscope.
Copyright: https://www.science.org/doi/10.1126/sciadv.abg1322

Publications
1. A. Nakamura, T. Shimojima, and K. Ishizaka, “Visualizing optically-induced strains by ﬁve-dimensional
ultrafast electron microscopy”, Faraday Discuss. 237, 27-39 (2022).
2. T. Shimojima, A. Nakamura, X. Z. Yu, K. Karube, Y. Taguchi, Y. Tokura, K. Ishizaka,“Nano-to-micro
spatiotemporal imaging of magnetic skyrmion’s life cycle”, Sci. Adv. 7, eabg1322/1-8 (2021).
3. A. Nakamura, T. Shimojima, Y. Chiashi, M. Kamitani, H. Sakai, S. Ishiwata, H. Li, and K. Ishizaka,“Nanoscale Imaging of Unusual Photoacoustic Waves in Thin Flake VTe2”, Nano Lett. 20, 7, 4932 (2020).
4. N. Mitsuishi, T. Shimojima, K. Ishizaka et al., “Switching of band inversion and topological surface states bycharge density wave”, Nature Commun. 11, 2466 (2020).
5. T. Shimojima, Y. Suzuki, A. Nakamura, N. Mitsuishi, S. Kasahara, T. Shibauchi, Y. Matsuda, Y. Ishida, S.
Shin and K. Ishizaka, “Ultrafast nematic-orbital excitation in FeSe”, Nature Commun. 10, 1946 (2019).

16Core members(Senior Research Scientist) Takahiro Shimojima(Research Scientist) Asuka Nakamura(Postdoctoral Researcher) Natsuki Mitsuishi

Strongly Correlated Spin Research Team
Hazuki Furukawa (Ph.D.), Team Leader
hazuki.furukawa@riken.jp
Research ﬁeld
Physics, Materials Science

Keywords
Strongly correlated electron system, Magnetism,
Superconductivity, Skyrmion, Neutron scattering

Brief resume
1995 Ph. D. in Physics, University of Tokyo
1995 Special researcher on Basic Science, The Institute ofPhysical and Chemical Research (RIKEN)

Study of relationship between magnetismand mechanism of superconductivity
in Ce(Co,Rh)In5
CeCoIn 5 has attracted particular attention among f-electron unconventional
superconductors because of the existence of resonance peaks, FFLO phases, andanomalous quasiparticles that appear in the superconducting phase. In addition, since
there is a quantum critical point associated with the antiferromagnetically ordered phasein the vicinity, magnetic ﬂuctuations are expected to contribute to the mechanism of its
superconductivity. So far, we have succeeded in identifying the Fermi surface that
contributes to the superconductivity of CeCoIn5 based on the results of neutron diffraction

1998 Research Associate, Oak Ridge National Lab.
1999 Associate Professor, Dep. of Physics, Faculty of
Science, Ochanomizu Univ.
1999 PRESTO, Japan Science and Technology Agency
2003 Full Professor, Dep. of Physics, Faculty of Science,
Ochanomizu Univ.
2007 Full Professor, Division of Natural/Applied Science,
Graduate School of Humanities and Sciences,
Ochanomizu University
2015 Full Professor, Faculty of Core Research Natural Science
Division, Ochanomizu University (-present)2016 Team Leader, Strongly Correlated Spin Research Team,
Strong Correlation Physics Division, RIKEN Center for
Emergent Matter Science (-present)

Outlineexperiments on Ce(Rh,Co)In 5, and have reported that the magnetic form factor in thissystem shows almost no magnetic ﬁeld dependence in the high magnetic ﬁeld region bysmall angle neutron scattering experiments. In this ﬁscal year, we further tried toinvestigate the interaction between magnetism and superconductivity in CeCoIn5 byfollowing the resonance peaks in
CeRh0.2Co0.8In5 by inelastic neutron
scattering experiments, and founda new magnetic ordered phase.
We need to investigate further thisphase to reveal the mechanism of
superconductivity in CeCoIn 5 indetail.

Magnetic scattering observed along (0.5 0.5 L) at 0.7K.

Publications
1. M. Soda, M. Kofu, S. Ohira-Kawamura, S. Asai, T. Masuda, H. Yoshizawa, H. Kawano-Furukawa,
Magnetic Diffuse and Quasi-Elastic Scatterings in Frustrated Magnet YBaCo4O7, J. Phys. Soc. Japan, 91(9), 0947072022, (2022).
2. M. Soda, N. Kagamida, S.Mühlbauer, E. Campillo, E. M Forgan,M. Kriener, H. Yoshizawa, H.
Kawano-Furukawa, Penetration Depth and Coherence Length in the Superconductor β-PdBi2, J. Phys.
Soc. Japan, 91 (3), 0347062022,(2022).
3. M. Soda, N. Kagamida, S.Mühlbauer, E. M Forgan, E. Campillo, M. Kriener, H. Yoshizawa, H.
Kawano-Furukawa, Field Dependence of Superﬂuid Density in β-PdBi2, J. Phys. Soc. Japan, 90 (10),104710, (2021).
4. M. Soda, K. Morita, G. Ehlers, F. Ye, T. Tohyama, H. Yoshizawa, T. Masuda, H. Kawano-Furukawa,
Magnetic Diffuse Scattering of YBaCo4O7 and LuBaCo4O7 on Kagome and Triangular Lattices, J. Phys.
Soc. Japan, 90 (7), 074704, (2021).
5. M. Soda, S. Itoh, T. Yokoo, G. Ehlers, H. Kawano-Furukawa, T. Masuda, “Magnetic correlations in on
kagome and triangular lattices”, Phys. Rev. B, 101, 214444 (2020).

Our team studies the static and dynamic magnetic
and atomic structure of strongly correlated electron
systems using various neutron scattering techniques.
We are working to verify the relevance of physicalcharacteristics in controlling and enhancing the
behavior of these systems.
Research topics include; (1) Elucidation of the role ofspin-orbit interactions in quantum states of newly
discovered exotic superconductors, (2) Veriﬁcation of
FFLO phase and/or helical vortex phase, and (3) Studyof the dynamics of skyrmions in topological magnetic
materials.

Core members(Technical Scientist) Edward Foley

17

Strong Correlation Physics Division

Electronic States Microscopy Research Team
Xiuzhen Yu (D.Sci.), Team Leader
yu_x@riken.jp
Research ﬁeld
Physics, Engineering, Materials Science

Keywords
Electronic states, Lorentz microscopy, Analyticalelectron microscopy, High-resolution electron
microscopy, Differential phase-contrast microscopy,
3D magnetic imaging

Brief resume
1990 Master, Department of Semiconductor, Jilin University

Real-Space Observations ofThree-Dimensional Antiskyrmions andSkyrmion Strings
The spin whirl, magnetic skyrmion carrying a topological number −1, attracts muchattention in fundamental physics and spintronics. As an antiparticle of skyrmion, the2002 Technician, Tokura Spin Superstructure Project, ERATO,
Japan Science and Technology Agency
2006 Engineer, Advanced Electron Microscopy Group,
Advanced Nano Characterization Center, NIMS
2008 Doctor of Science, Department of Physics, Tohoku
University
2008 Researcher, Advanced Electron Microscopy Group,
Advanced Nano Characterization Center, NIMS

antiskyrmion exhibits opposite topological charge and unique spin texture composed of2010 Researcher, Tokura Multiferroic Project, ERATO, Japan
Science and Technology Agency

the alternating Bloch- and Néel-type spirals. The present research aims to understand2011 Postdoctoral Researcher, Quantum Science on Strong
Correlation Group, Advanced Science Institute, RIKEN

nontrivial 3D forms of topological objects and explore emergent electromagnetic
properties in magnetic materials. We developed tomographic Lorentz TEM with a highspatial resolution (5 nm), and built an algorithm for 3D vector ﬁeld reconstruction, allowing
real-space observation of 3D topological spin textures, such as the deformed skyrmion
string (Fig. 1a). Figure 1b shows the scalar ﬁeld maps of some skyrmion strings in the2013 Senior Research Scientist, Strong Correlation Physics
Research Group, Strong Correlation Physics Division,
RIKEN Center for Emergent Matter Science (CEMS)
2017 Team Leader, Electronic States Microscopy Research
Team, RIKEN CEMS (-present)

Outlinetop-view (upper panel) and cross-section view (downpanel). The dual-tilt series of 2D Lorentz TEM images
were employed to demonstrate a 3D vector ﬁeld mapof the antiskyrmion (Fig. 1c). Systematic analyses of
the tilt series of Lorentz TEM images allow us to build
3D phase images (Fig. 1d) and the corresponding
vector ﬁeld maps of a single antiskyrmion and its
cluster (Figs. 1e-f).
Our exploits will lead to an advanced understandingof 3D spin textures in a broad class of magnets.
(a) Schematic of a deformed skyrmion string. (b) 3D scalar ﬁeld map of some skyrmions strings
observed in the top-view (upper panel) and the cross-section view (down panel) in a CoZnMn alloy.
(c) The schematic of an antiskyrmion. (d-f) The 3D phase image (d) and corresponding vector ﬁeld
maps of antiskyrmions (e-f).

Publications
1. X. Z. Yu, K. V. Iakoubovskii, F. S. Yasin, L. Peng, K. Nakajima, S, Schneider, K. Karube, T. Arima, Y. Taguchi,
Y. Tokura, “Real-space observations of three-dimensional antiskyrmions and skyrmion strings”, Nano Lett.,
23, 9358 (2022).
2. F. S. Yasin, J. Masell, K. Karube, A. Kikkawa, Y. Taguchi, Y. Tokura and X. Z. Yu, “Real-space determinationof the isolated magnetic skyrmion deformation under electric current ﬂow”, Natl. Acad. Sci. U.S.A., 119,e2200958119 (2022).
3. X. Z. Yu, F. Kagawa, S. Seki, M. Kubota, J. Masell, F. S. Yasin, K. Nakajima, M. Nakamura, M. Kawasaki,
N. Nagaosa and Y. Tokura, “Real-space observations of 60-nm skyrmion dynamics in an insulating magnet
under low heat ﬂow”, Nat. Commun., 12, 5079 (2021).
3. N. D. Khanh, T. Nakajima, X. Z. Yu, S. Gao, K. Shibata, M. Hirschberger, Y. Yamasaki, H. Sagayama, H.
Nakao, L. Peng, K. Nakajima, R. Takagi, T. Arima, Y. Tokura, S. Seki, “Nanometric square skyrmion latticein a centrosymmetric tetragonal magnet”, Nat. Nanotechnol., 15, 444 (2020).
5. X. Z. Yu, W. Koshibae, Y. Tokunaga, K. Shibata, Y. Taguchi, N. Nagaosa and Y. Tokura, “Transformation
between meron and skyrmion topological spin textures in a chiral magnet”, Nature, 564, 95 (2018).

18

Our team is working on the real-space observation ofelectron structures or topological electron-spin textures(skyrmion) and their dynamics in strong-correlation
systems by means of atomic-resolution electron
microscopy. We use various microscopies, such as thein-situ imaging technique, differential phase-contrast
microscopy, 3D magnetic imaging, electronenergy-loss spectroscopy, and energy dispersive
spectroscopy, etc., to explore the electronic structures
and their dynamical phase transitions with external
stimuli. We also use these powerful tools toquantitatively characterize the nanometric magnetic
and electric ﬁelds in topological matters to exploit
emergent phenomena and hence their possible
applications in the spintronics.

Core members(Special Postdoctoral Researcher) Fehmi Sami Yasin(Postdoctoral Researcher) Yao Guang, Shunsuke Mori
(Technical Scientist) Yi Ling Chiew(Technical Staff I ) Kiyomi Nakajima

Emergent Photodynamics Research Team
Naoki Ogawa (D.Eng.), Team Leader
naoki.ogawa@riken.jp
Research ﬁeld
Physics, Materials Science, Engineering

Keywords
Strongly correlated electron systems, Quantum
materials, Ultrafast/broadband optical spectroscopy,
Photocurrent spectroscopy, Opto-spintronics

Brief resume
2004 D. Eng., University of Tokyo
2004 Postdoctoral Associate, University of California at Irvine

Optical diode effect insecond harmonic generation
In multiferroic materials where spatial-inversion and time-reversal symmetries are
simultaneously broken, optical responses can change by reversing the direction of lightpropagation. This nonreciprocal effect has been realized in various linear optical2004 Research Fellow of the Japan Society for the Promotionof Science
2006 Project Assistant Professor, University of Tokyo
2008 Assistant Professor, University of Tokyo
2012 ASI Research Scientist, RIKEN
2013 Senior Research Scientist, RIKEN Center for Emergent
Matter Science

responses, such as transmission, emission, scattering, and refraction. We investigate the2015 Unit Leader, Emergent Photodynamics Research Unit,
Cross-Divisional Materials Research Program, RIKEN
Center for Emergent Matter Science

nonreciprocal effects in nonlinear optical processes, speciﬁcally second harmonic2017 JST PRESTO Researcher

generation (SHG) in CuB2O4. Generally, nonreciprocal effects are negligibly small, because

2018 Team Leader, Emergent Photodynamics Research Team,RIKEN Center for Emergent Matter Science (-present)

their origin is an interference between magnetic and electric dipole transitions, where the2020 Guest Professor, University of Tokyo

former is intrinsically much smaller than the latter. We found that the magnetic dipole
transition in CuB2O4 can be enhanced extremely due to optical resonance, leading to the

Outlinemagnitude comparable to that of the electric dipole one under the non-resonantcondition. As a result, the two transitions interfere with each other in the same phase andamplitude, resulting in an almost perfect nonlinear nonreciprocal effect with 97% change
in the SHG intensity. We also demonstrated that the direction with the larger SHG
intensity can be controlled by reversing a magnetic ﬁeld of only 10 mT.

(Left) Schematic illustration of nonreciprocal SHG.
(Right) Magnetic ﬁeld dependence of SHG intensity.

Publications

Publications

1. S. Toyoda, R. Yamada, Y. Kaneko, Y. Tokura, and N. Ogawa, ”Weyl fermions in SrRuO3 detected by
Brillouin light scattering”, Appl. Phys. Lett., 120, 242408 (2022).
2. S. Toyoda, M. Fiebig, L. Forster, T. Arima, Y. Tokura, and N. Ogawa, ”Writing of strain-controlled
multiferroic ribbons into MnWO4”, Nature Commun., 12, 6199 (2021).

Our team explores novel photodynamics ofelectron/spin/lattice in bulk crystals and at thin-ﬁlm
interfaces emerging via electron-correlation, strong
spin-orbit interaction, and topology. Examples areultrafast spectroscopy of shift/injection current,
generation of spin current mediated by Dirac/Weylelectrons, and manipulation of topological magnetic
textures. With a strong command of photons, we try
to realize new photo-electric/magnetic effects insolids, and visualize spatiotemporal propagation ofvarious elemental excitations at the sub-diffraction
limit.

Core members(Postdoctoral Researcher)
Ziqian Wang, Jannis Lehmann, Yajian Hu

3. S. Toyoda, M. Fiebig, T. Arima, Y. Tokura, and N. Ogawa, “Nonreciprocal second harmonic generation ina magnetoelectric material”, Sci. Adv. 7, eabe2793 (2021).
4. N. Ogawa, L. Köhler, M. Garst, S. Toyoda, S. Seki, and Y. Tokura, “Nonreciprocity of spin-waves in theconical helix state”, Proc. Natl. Acad. Sci., 118, e2022927118 (2021).
5. M. Sotome, M. Nakamura, J. Fujioka, M. Ogino, Y. Kaneko, T. Morimoto, Y. Zhang, M. Kawasaki, N.
Nagaosa, Y. Tokura, and N. Ogawa, “Spectral dynamics of shift-current in ferroelectric semiconductor
SbSI”, Proc. Natl. Acad. Sci., 116, 1929 (2019).

19

Strong Correlation Physics Division

Dynamic Emergent Phenomena Research Team
Fumitaka Kagawa (D.Eng.), Team Leader
fumitaka.kagawa@riken.jp
Research ﬁeld
Materials Science, Physics

Keywords
Strongly correlated electron system, Phase control,
Scanning probe microscopy, Spectroscopy

Brief resume
2006 D.Eng., University of Tokyo
2006 Research fellowship for young scientists
2007 Researcher, JST-ERATO Multiferroic project

Kinetic approach to superconductivity
hidden behind a competing order2010 Project Lecturer, Quantum-Phase Electronics Center,
University of Tokyo
2012 Lecturer, Department of Applied Physics, University ofTokyo

In strongly correlated electron systems, the emergence of superconductivity is often
inhibited by the formation of a thermodynamically more stable magnetic/charge order.
Nevertheless, by changing thermodynamic parameters, such as the physical/chemicalpressure and carrier density, the free-energy balance between the superconductivity andthe competing order can be varied, thus enabling the superconductivity to develop as thethermodynamically most stable state. We demonstrate a new kinetic approach to
avoiding the competing order and thereby inducing persistent superconductivity. In the2013 Unit Leader, Dynamic Emergent Phenomena Research
Unit, Cross-Divisional Materials Research Program,
RIKEN Center for Emergent Matter Science2017 Associate Professor, Department of Applied Physics,
University of Tokyo
2022 Professor, Department of Physics, Tokyo Institute ofTechnology (-present)
2022 Team Leader, Dynamic Emergent Phenomena
Research Team, RIKEN Center for Emergent Matter
Science (-present)

transition-metal dichalcogenide IrTe2 as an example, by utilizing current-pulse-based rapid
cooling up to ~107 K s-1, we successfully kinetically avoid a ﬁrst-order phase transition to

Outlinea competing charge order and uncover metastable superconductivity hidden behind. The
present method also enables non-volatile and reversible switching of the metastablesuperconductivity with electric pulse applications, a unique advantage of the kinetic
approach. Thus, our ﬁndings provide a new approach to developing and controlling
IrTe2 thin plate

Thermodynamic
approach
First

ate

gr

olin

TungstenElectrode

r

10 μm

T = 2.4 K

RESET
SET

1.5

Superconductivity
Composition, PressureCo

Si Substrate

2.0

Competingorder

Metastable
SC

Gold
Electrode

ordeSuperconductivity

ρ (μΩ cm)

tic
ne ch
Ki roap
ap

Temperature

superconductivity.

1.0

0.5

0
0

100

200

300

400

Time (s)Conceptual phase diagram of superconductivity with ultra-rapid cooling (left), the thin-plate sample
used in the experiments (top right) and non-volatile switching between superconducting andnon-superconducting states demonstrated by resistivity measurements (bottom right)

Publications
1. T. Sato, W. Koshibae, A. Kikkawa, Y. Taguchi, N. Nagaosa, Y. Tokura, and F. Kagawa, “Nonthermal
current-induced transition from skyrmion lattice to nontopological magnetic phase in spatially conﬁned
MnSi”, Phys. Rev. B 106, 144425 (2022).
2. H. Oike, K. Takeda, M. Kamitani, Y. Tokura, and F. Kagawa, “Real-space observation of emergent
complexity of phase evolution in micrometer-sized IrTe2 crystals” Phys. Rev. Lett. 127, 145701 (2021).
3. K. Matsuura, H. Oike, V. Kocsis, T. Sato, Y. Tomioka, Y. Kaneko, M. Nakamura, Y. Taguchi, M. Kawasaki,
Y. Tokura, and F. Kagawa, “Kinetic pathway facilitated by a phase competition to achieve a metastableelectronic phase”, Phys. Rev. B 103, L041106 (2021).
4. H. Oike, M. Kamitani, Y. Tokura, and F. Kagawa, “Kinetic approach to superconductivity hidden behind acompeting order”, Sci. Adv., 4, eaau3489 (2018).
5. H. Oike, A. Kikkawa, N. Kanazawa, Y. Taguchi, M. Kawasaki, Y. Tokura, and F. Kagawa, “Interplay between
topological and thermodynamic stability in a metastable magnetic skyrmion lattice”, Nat. Phys., 12, 62(2016).

20

Our team explores dynamic phenomena exhibited bystrongly correlated electron systems in both bulk anddevice structures to construct a new scheme forscientiﬁc investigation. In particular, we study
external-ﬁeld-driven dynamic phenomena exhibited bysub-micron-scale structures, such as topological spin
textures and domain walls, using spectroscopy ofdielectric responses and resistance ﬂuctuations fromthe millihertz to gigahertz region. We also pursue
real-space observations and measurements of local
physical properties using scanning probe microscopy
as a complementary approach. We are aiming tocontrol novel physical properties exhibited by
topological structures in condensed matter systems
on the basis of knowledge obtained from thesemethods.

Core members(Postdoctoral Researcher) Meng Wang
(Visiting Scientist) Hiroshi Oike, Takuro SatoSupramolecular Chemistry Division

Emergent Soft Matter Function Research Group
Takuzo Aida (D.Eng.), Group Director
takuzo.aida@riken.jp
Research ﬁeld
Chemistry, Materials Science

Keywords
Soft material, Molecular design, Self-assembly, Energy
conversion, Biomimetics, Stimuli-responsive material,
Electronic material, Photoelectric conversion material,
Environmentally friendly material

Brief resume
1984 D.Eng., University of Tokyo

Chain-growth supramolecular polymerization
Over the last decade, signiﬁcant progress in supramolecular polymerization has had a1984 Research Assistant / Lecturer, University of Tokyo
1991 Associate Professor, University of Tokyo
1996 Professor, University of Tokyo (-present)

substantial impact on the design of functional soft materials. However, despite recent

2000 Project Leader, ERATO Aida Nanospace Project, Japan
Science and Technology Corporation

advances, most studies are still based on a preconceived notion that supramolecular2007 Group Director, Responsive Matter Chemistry &Engineering Research Group, RIKEN

polymerization follows a step-growth mechanism. We recently realized the ﬁrst
chain-growth supramolecular polymerization by designing metastable monomers with a2010 Group Director, Functional Soft Matter Research Group,
RIKEN

shape-promoted intramolecular hydrogen-bonding network. The monomers are2011 Team Leader, Photoelectric Conversion Research Team,
RIKEN

conformationally restricted from spontaneous polymerization at ambient temperatures but

2013 Deputy Director, RIKEN Center for Emergent Matter
Science (CEMS) (-present)

begin to polymerize with characteristics typical of a living mechanism upon mixing with
tailored initiators. The chain growth occurs stereoselectively and therefore enables opticalresolution of a racemic monomer. We believe that it may give rise to a paradigm shift inprecision macromolecular engineering.

2013 Group Director, Emergent Soft Matter Function
Research Group, Division Director, Supramolecular
Chemistry Division, RIKEN CEMS (-present)
2022 Distinguished University Professor, University of Tokyo(-present)

OutlineSchematic illustration of chain-growth supramolecular polymerization

Publications
1. Y. Itoh, S. Chen, R. Hirahara, T. Aoki, T. Ueda, I. Shimada, J. J. Cannon, C. Shao, J. Shiomi, K. V. Tabata,H. Noji, K. Sato, and T. Aida, “Ultrafast water permeation through nanochannels with a densely ﬂuorous
interior surface”, Science, 376, 738 (2022).
2. Z. Chen, Y. Suzuki, A. Imayoshi, X. Ji, K. V. Rao, Y. Omata, D. Miyajima, E. Sato, A. Nihonyanagi, and T.
Aida, “Solvent-free autocatalytic supramolecular polymerization”, Nature Mater., 21, 253 (2022).
3. W. Meng, S. Kondo, T. Ito, K. Komatsu, J. Pirillo, Y. Hijikata, Y. Ikuhara, T. Aida, and H. Sato, “An elastic
metal-organic crystal with densely catenated backbone”, Nature, 598, 298 (2021).
4. H. Huang, H. Sato, J. Pirillo, Y. Hijikata, Y. S. Zhao, S. Z. D. Cheng, and T. Aida, “Accumulated latticestrain as an internal trigger for spontaneous pathway selection”, J. Am. Chem. Soc., 143, 15319 (2021).

With world's focus on environment and energy issues,
our group aims to establish a novel principle ofmaterial sciences addressing these problems, throughthe development of unprecedented functional
materials with precisely controlled structure andproperties at molecular to nanoscale levels. The main
research subjects include (1) the development of novel
organic catalysts consisting only of ubiquitouselements for high efﬁcient water photolysis, (2) the
development of the solution-processable organic
ferroelectric materials for the application to memoryd e v i c e s , a n d ( 3 ) t h e d e v e l o p m e n t o f p re c i s esupramolecular polymerizations.

Core members(Research Scientist) Nobuhiko Mitoma, Hubiao Huang(Visiting Researcher) Abir Goswami, Zebin Su(Technical Staff) Motonobu Kuwayama(Student Trainee) Gangfeng Chen, Yiren Cheng,
Yang Hong, Niannian Wu

5. Y. Yanagisawa, Y. Nan, K. Okuro, and T. Aida, “Mechanically robust, readily repairable polymers via
tailored noncovalent cross-linking”, Science, 359, 72 (2018).

21

Supramolecular Chemistry Division

Emergent Molecular Function Research Team
Kazuo Takimiya (D.Eng.), Team Leader
takimiya@riken.jp
Research ﬁeld
Chemistry, Engineering, Materials Science

Keywords
Organic semiconductor, Pi-electronic compound,
Organic Synthesis, Organic ﬁeld-effect transistor,
Organic solar cells, Organic thermoelectric materials

Brief resume
1994 Ph.D., Hiroshima University

Development of high-mobility
organic semiconductors bycontrolling molecular arrangement

1994 Research Associate, Hiroshima University
1997 Visiting Researcher, Odense University, Denmark
2003 Associate Professor, Hiroshima University
2007 Professor, Hiroshima University
2012 Team Leader, Emergent Molecular Function Research
Team, RIKEN

dependent not only on the molecular structure but also packing structure and molecular2013 Group Director, Emergent Molecular Function ResearchGroup, Supramolecular Chemistry Division, RIKEN
CEMS

orientation in the solid state. However, it is very difﬁcult to predict and control the crystal

2017 Professor, Tohoku University (-present)

structure at the stage of molecular design, and the development of methodologies for2018 Team Leader, Emergent Molecular Function Research
Team, Supramolecular Chemistry Division, RIKEN Center
for Emergent Matter Science (-present)

Solid-state properties of organic semiconductors, e.g., carrier mobility, are largely

controlling the crystal structure of organic semiconductors is an important issue. We havefound that it is possible to lead to a crystal structure suitable for high mobility byintroducing a simple substituent such as a methylthio group at an appropriate position in

Outlinethe organic semiconductor skeleton. For example, When four methylthio groups wereregio-selectively introduced into pyrene that crystalizes into a sandwich herringbone
structure, the crystal structure changes dramatically into a brickwork structure, whichenables two-dimensional conduction. The carrier mobility evaluated by using
single-crystal ﬁeld-effect transistors was higher than 30 cm2 V-1 s-1, which was among thehighest for organic semiconductors.

Development of high-mobility organic semiconductors by controlling molecular arrangement

Publications
1. K. Bulgarevich, S. Horiuchi, T. Ogaki, K. Takimiya, “1,3,6,8-Tetrakis(methylchalcogeno)pyrenes: Effects ofChalcogen Atoms on Crystal Structure and Transport Properties”, Chem. Mater., 34, 6606 (2022).
2. K. Takimiya, K. Bulgarevich, S. Horiuchi, A. Sato, K. Kawabata, “Band-like versus
temperature-independent carrier transport in isomeric diphenyldinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophenes (DPh-DNTTs)”, ACS Mater. Lett., 4, 675 (2022).
3. K. Takimiya, Kirill Bulgarevich, M. Abbas, S. Horiuchi, T. Ogaki, K. Kawabata, A. Ablat,““Manipulation” ofcrystal structure by methylthiolation enabling ultrahigh mobility in a pyrene-based molecular
semiconductor”, Adv. Mater., 33, 2102914 (2021).
4. Y. Wang, K. Takimiya, “Naphthodithiophenediimide–Bithiopheneimide Copolymers for High-Performancen-Type Organic Thermoelectrics: Signiﬁcant Impact of Backbone Orientation on Conductivity and
Thermoelectric Performance”, Adv. Mater., 32, 2002060 (2020).
5. C. Wang, D. Hashizume, M. Nakano, T. Ogaki, H. Takenaka, K. Kawabata, K. Takimiya, ““Disrupt andInduce” Intermolecular Interactions to Rationally Design Organic Semiconductor Crystals: from
Herringbone to Rubrene-like Pitched S-Stack”, Chem. Sci. 11, 1573 (2020).

22

Our research activity is based upon organic synthesisthat can afford new organic materials utilized in
optoelectronic devices, such as organic ﬁeld-effecttransistors (OFETs), organic solar cells (organic
photovoltaics, OPVs), and organic thermoelectric
devices (OTE). To this end, our team develops neworganic materials, which can be designed andsynthesized in order to have appropriate molecularand electronic structures for target functionalities. Our
recent achievements are: 1) high-performancemolecular semiconductors applicable to OFETs withthe high mobilities, 2) new non-fullerene acceptors andtheir OPVs showing high power conversion
efﬁciencies, and 3) new molecular design strategies tocontrol packing structures of organic semiconductors.

Core members(Researcher) Barun Dhara(Postdoctoral Researcher) Masanori Sawamoto,
Kirill Bulgarevich, Haruki Sanematsu(Visiting Scientist) Jisoo Shin, Kohsuke Kawabata(Student trainee) Shingo Horiuchi

Emergent Bioinspired Soft Matter
Research Team
Yasuhiro Ishida (D.Eng.), Team Leader
y-ishida@riken.jp
Research ﬁeld
Chemistry, Materials Science

Keywords
Self-assembly, Biomimetics, Soft material,
Stimuli-responsive material, Environmentally friendly
material

Brief resume
2001 D.Eng., University of Tokyo

Synthetic hydrogel like cartilage,
but with a simpler structure- Potential as artiﬁcial cartilage and anti-vibration materials Electrostatic and magnetic repulsive forces are used in various places, as in maglev trains,

2001 Assistant Professor, Graduate School of Frontier
Sciences, University of Tokyo
2002 Assistant Professor, Graduate School of Engineering,
University of Tokyo
2007 Lecturer, Graduate School of Engineering, University ofTokyo2007 Researcher, PRESTO, Japan Science and Technology
Agencyvehicle suspensions or non-contact bearings etc. However, design of polymer materials,

2009 Team Leader, Nanocomposite Soft Materials Engineering
Team, RIKEN

such as rubbers and plastics, has focused overwhelmingly on attractive interactions for their2010 Team Leader, Bioinspired Material Research Team,
RIKEN

reinforcement, while little attention has been given to the utility of internal repulsive forces.
Nevertheless, in nature, articular cartilage in animal joints utilizes an electrostatically repulsive
force for insulating interfacial mechanical friction even under high compression.
We discovered that when nanosheets of unilamellar titanate, colloidally dispersed in an2013 Team Leader, Emergent Bioinspired Soft Matter
Research Team, Supramolecular Chemistry Division,
RIKEN Center for Emergent Matter Science (-present)

Outlineaqueous medium, are subjected to a strong magnetic ﬁeld, they align cofacial to one
another, where large and anisotropic electrostatic repulsion emerges between thenanosheets. This magneto-induced temporal structural ordering can be ﬁxed bytransforming the dispersion into a hydrogel. The anisotropic electrostatics thus embedded
allows the hydrogel to show unprecedented mechanical properties, where the hydrogel easy
deforms along a shear force applied parallel to the nanosheet plane but is highly resistive
against a compressive force applied orthogonally.
The concept of embedding repulsive electrostatics in a composite material, inspired fromarticular cartilage, will open new possibilities for developing soft materials with unusualfunctions.

Hydrogel embeddedwith an anisotropic
electrostatic repulsive
force.

Publications
1. K. Sano, X. Wang, Z. Sun, S. Aya, F. Araoka, Y. Ebina, T. Sasaki, Y. Ishida, and T. Aida, “Propagating
wave in a ﬂuid by coherent motion of 2D colloids”, Nat. Commun., 12, 6771 (2021).
2. K. Sano, N. Igarashi, Y. Ebina, T. Sasaki, T. Hikima, T. Aida, and Y. Ishida, “A mechanically adaptivehydrogel with a reconﬁgurable network consisting entirely of inorganic nanosheets and water”, Nat.
Commun., 11, 6026 (2020).
3. K. Salikolimi, V. K. Praveen, A. A. Sudhakar, K. Yamada, N. N. Horimoto, and Y. Ishida, “Helicalsupramolecular polymers with rationally designed binding sites for chiral guest recognition”, Nat.
Commun., 11, 2311 (2020).

Owing to intrinsic similarity to living organisms, suchas lightweight, softness, and biocompatibility, soft
materials have attracted increasing attention forbiomedical applications, including artiﬁcial organs.
However, in terms of structure, there is a signiﬁcantdifference between synthetic soft materials and livingorganisms; most synthetic soft materials are ofisotropic structures, while living tissues are anisotropic.
As seen in muscular, bone, and nerval textures, suchanisotropic structures play critical roles for exhibiting
their superb functions. By using external ﬁelds fororienting constituents, we have developed various
anisotropic soft materials with highly oriented structure
and unprecedented unique functions reminiscent ofliving organisms.

Core members(Expert Technician) Kuniyo Yamada(Research Scientist) Xiang Wang
(Technical Staff) Hayato Kanai(Student Trainee) Shuxu Wang, Xiaoyao Wei

4. Y. S. Kim, M. Liu, Y. Ishida, Y. Ebina, M. Osada, T. Sasaki, T. Hikima, M. Takata, and T. Aida,“Thermoresponsive actuation enabled by permittivity switching in an electrostatically anisotropichydrogel”, Nat. Mater., 14, 1002 (2015).
5. M. Liu, Y. Ishida, Y. Ebina, T. Sasaki, T. Hikima, M. Takata, and T. Aida, “An anisotropic hydrogel withelectrostatic repulsion between cofacially aligned nanosheets”, Nature, 517, 68 (2015).

23

Supramolecular Chemistry Division

Emergent Device Research Team
Yoshihiro Iwasa (D.Eng.), Team Leader
iwasay@riken.jp
Research ﬁeld
Physics, Engineering, Chemistry, Materials Science

Keywords
2D materials, Nanotubes, Quantum dots,
Superconductivity, Thermoelectric effect,
Nonreciprocal transport, Anomalous photovoltaic
effectBrief resume
1986 Ph. D., University of Tokyo

Bulk photovoltaic effectinduced by symmetry control of
two-dimensional materials
Our team is studying nonreciprocal transport in semiconductors and superconductors.
One of them is a bulk photovoltaic effect, where the photoelectric conversion occurs
without PN junctions.
Monolayer transition metal dichalcogenides (TMDs) are two-dimensional materials withthree-fold symmetry, which are known not to exhibit bulk photovoltaics. However, such ananomaterial is capable of changing symmetry either by deforming or creating

1986 Research Associate, Department of Applied Physics,
University of Tokyo
1991 Lecturer, Department of Applied Physics, University ofTokyo
1994 Associate Professor, School of Materials Science, Japan
Advanced Institute of Science and Technology
2001 Professor, Institute for Materials Research, Tohoku
University
2010 Professor, Quantum-Phase Electronics Center, Universityof Tokyo (-present)2010 Team Leader, Strong-Correlation Hybrid Materials
Research Team, RIKEN
2013 Team Leader, Emergent Device Research Team,Supramolecular Chemistry Division, RIKEN Center for
Emergent Matter Science (-present)

heterojunctions. This is a unique and important feature of nanomaterials that distinguishes
them from bulk. Speciﬁcally, we have found strong bulk photovoltaic effects in the visible

Outlineto infrared region in WS2 nanotubes, WSe2/black phosphorus van Waals heterojunctions,and strained MoS2 (Refs. 1, 3, 5). We found that the shift current mechanism plays animportant role in this photovoltaic effect. Symmetry-controlled nanomaterials showing
such large photovoltaic effects
will be a promising new
platform for high-efﬁciency
photovoltaics and sensors.

Left: Symmetry controlled TMDｓ. From the top, TMD nanotube, van der Waals heterostructure, andstrained device. Copylight: Adapted from “Nature Nanotechnology 18, 36 (2023).”
Right: Wave length dependence of bulk photovoltaic coefﬁcient for nano TMDs.

Publications
1.Publications
Y. Dong, M. -M. Yang, M. Yoshii, S. Matsuoka, S. Kitamura, T. Hasegawa, N. Ogawa, T. Morimoto, T.
Ideue, Y. Iwasa, "Giant bulk piezophotovoltaic effect in 3R-MoS2", Nat. Nanotechnol., 18, 36-41 (2023).
2. Y. Nakagawa, Y. Kasahara, T. Nomoto, R. Arita, T. Nojima, Y. Iwasa, "Gate-controlled BCS-BEC crossoverin a two-dimensional superconductor", Science, 372, 190 (2021).
3. T. Akamatsu, T. Ideue, L. Zhou, Y Dong, S. Kitamura, M. Yoshii, D. Yang, M. Onga, Y. Nakagawa, K.
Watanabe, T. Taniguchi, J. Laurienzo, J. Huang, Z. Ye, T. Morimoto, H. Yuan, Y. Iwasa, “A van der Waals
interface that creates in-plane polarization and a spontaneous photovoltaic effect”, Science, 372, 68-72(2021).
4. R. Miranti, D. Shin, R. D. Septianto, M. Ibáñez, M. V. Kovalenko, N. Matsushita, Y. Iwasa, S. Z. Bisri,“Exclusive Electron Transport in Core@Shell PbTe@PbS Colloidal Semiconductor Nanocrystal
Assemblies”, ACS Nano, 14, 3242-3250 (2020).
5. Y. J. Zhang, T. Ideue, M. Onga, F. Qin, R. Suzuki, A. Zak, R. Tenne, J. H. Smet, and Y. Iwasa, “Enhanced
intrinsic photovoltaic effect in tungsten disulﬁde nanotubes”, Nature, 570, 349-353 (2019) .

24

The purpose of our team is to discover novel
properties and create revolutionary functions, basedon nanodevices of two-dimensional (2D) materials, 1D
nanotubes, and 0D quantum dots (QD) of various
oxides and chalcogenides. Our focus issuperconductivity, phase transitions, andnonreciprocal transport, using 2D materials and theirvan der Waals heterostructures, and a wide range ofcarrier density tuning using electric double layertransistors. We also develop several novel
solution-processable QDs, assemble them into various
arrangements, and realize various functionalities
including thermoelectricity, photovoltaics, and chargestorage.

Core members(Special Postdoctoral Researcher) Hideki Matsuoka(Postdoctoral Researcher) Ricky Dwi Septianto(International Program Associate)
Retno Dwi Wulandari, Thanyarat Phutthaphongloet,
Alec Paul Romagosa

Emergent Soft System Research Team
Takao Someya (Ph.D.), Team Leader
takao.someya@riken.jp
Research ﬁeld
Electronic Engineering, Materials Science

Keywords
Organic electronics, Organic ﬁeld-effect transistor,
Organic light emitting devices, Organic solar cells,
Organic sensors

Brief resume
1997 Ph.D., Electronic Engineering, University of Tokyo

Ultraﬂexible, high-performanceand stable organic solar cells

1997 Research Associate, University of Tokyo
1998 Lecturer, University of Tokyo
2001 JSPS Postdoctoral Fellowship for Research Abroad(Columbia University)
2002 Associate Professor, University of Tokyo

One of the requirements of the Internet of Things—referring to a world where devices ofall sorts are connected to the Internet—is the development of power sources for a host ofdevices, including devices that can be worn on the body. These could include sensors
that record heartbeats and body temperature, for example, providing early warning of2009 Professor, University of Tokyo (-present)2015 Chief Scientist, Thin-ﬁlm deice lab, RIKEN (-present)2015 Team Leader, Emergent Soft System Research Team,Supramolecular Chemistry Division, RIKEN CEMS(-present)

medical problems. In the past, attempts have been made to create photovoltaics that
could be incorporated into textiles, but typically they lacked at least one of the important

Outlineproperties—long-term stability in both air and water, energy efﬁciency, and robustness
including resistance to deformation—that are key to successful devices.
We have developed an ultraﬂexible organic photovoltaic (OPV) that achieves sufﬁcient
thermal stability of up to 120 °C and a high power conversion efﬁciency of 13% with a
total thickness of 3 μm. Additionally, our ultraﬂexible organic solar cells exhibit prolonged
device storage lifetime to >3,000 h at room temperature. Our ultraﬂexible OPVs
possessing extraordinary thermal durability allow a facile bonding onto textiles through the
hot-melt adhesive technology.

(Left) Ultraﬂexible organic solar cells manufactured on a 1 μm-thick plastic ﬁlm.
(Right) Photograph of the washing process for the devices conforming to a dress shirt.

Publications
1. Z. Jiang, N. Chen, Z. Yi, J. Zhong, F. Zhang, S. Ji, R. Liao, Y. Wang, H. Li, Z. Liu, Y. Wang, T. Yokota, X. Liu,
K. Fukuda, X. Chen, and T. Someya, “A 1.3-micrometre-thick elastic conductor for seamless on-skin andimplantable sensors”, Nat. Electron., 5, 784-793 (2022).
2. Y. Kakei, S. Katayama, S. Lee, M. Takakuwa, K. Furusawa, S. Umezu, H. Sato, K. Fukuda, and T. Someya,“Integration of body-mounted ultrasoft organic solar cell on cyborg insects with intact mobility”, npj Flex.
Electron., 6, 78 (2022).
3. M. Takakuwa, K. Fukuda, T. Yokota, D. Inoue, D. Hashizume, S. Umezu, T. Someya, “Direct gold bonding
for ﬂexible integrated electronics”, Sci. Adv., 7, eabl6228 (2021).
4. Z. Jiang, F. Wang, K. Fukuda, A. Karki, W. Huang, K. Yu, T. Yokota, K. Tajima, T.-Q. Nguyen, and T.
Someya, “Highly efﬁcient organic photovoltaics with enhanced stability through the formation of
doping-induced stable interfaces”, PNAS, 117, 6391-6397 (2020).

Electronics is expected to support the foundation ofhighly develop ICT such as Internet of Things (IoT),
artiﬁcial intelligence (AI), and robotics. In addition to
improve the computing speed and storage capacity, it
is required to minimize negative impact of machines
on environment and simultaneously to realize theharmony between human and machines. We make fulluse of the novel soft electronic materials such as novel
organic semiconductors in order to fabricate emergent
thin-ﬁlm devices and, subsequently, to realize
emergent soft systems that exhibit super-high
efﬁciency and harmonization with humans. The newsoft systems have excellent features such as
lightweight and large area, which are complimentary to
inorganic semiconductors, are expected to open up
new eco-friendly applications.

Core members(Senior Research Scientist) Kenjiro Fukuda(Postdoctoral Researcher) Sixing Xiong, Ruiqi Guo(Senior Technical Staff) Shin Young Lee(Student Trainee) Jiachen Wang, Baocai Du,
Wenqing Wang, Tatsuma Miyake,
Shumpei Katayama. Kundi Zhao

5. S. Park, S.-W. Heo, W. Lee, D. Inoue, Z. Jiang, K. Yu, H. Jinno, D. Hashizume, M. Sekino, T. Yokota, K.
Fukuda, K. Tajima, and T. Someya “Self-powered ultra-ﬂexible electronics via nano-grating-patternedorganic photovoltaics”, Nature, 551, 516-521 (2018).

25

Supramolecular Chemistry Division

Emergent Functional Polymers Research Team
Keisuke Tajima (Ph.D.), Team Leader
keisuke.tajima@riken.jp
Research ﬁeld
Chemistry, Engineering, Materials Science

Keywords
Organic electronics, Organic solar cells, Polymer
synthesis, Self-assembly, Nanostructure control

Brief resume
2002 Ph.D., The University of Tokyo
2002 Postdoctoral Researcher, Northwestern University

Energetic driving force forcharge generation in organic solar cells
For further improvement of the device performance of organic solar cells, optimizationof electron-donating material and electron-accepting material is necessary. However, weﬁrst need to know the most suitable electronic structures for these materials. The problem
was the lack of knowledge on the relation between the energetic driving force at the2004 Research Associate, The University of Tokyo
2009 Lecturer, The University of Tokyo
2011 Associate Professor, The University of Tokyo
2011 PRESTO Researcher, Japan Science and Technology
Agency (-2017)2012 Team Leader, Emergent Functional Polymers Research
Team, RIKEN
2013 Team Leader, Emergent Functional Polymers Research
Team, Supramolecular Chemistry Division, RIKEN Center
for Emergent Matter Science (-present)

donor and acceptor interface and resulting device performance. To investigate therelationship between the interfacial energetic driving force and resulting device

Outlineperformance, the planar-heterojunction structures with simple and well-deﬁned interfacesof electron-donating material (D) and electron-accepting material (A) are investigated. 16
planar-heterojunctions with four donor materials and four acceptor material weresystematically investigated. We found that for efﬁcient charge generation, molecularly
excited state (S1) and interfacial charge-transfer (CT) state must have an energetic
difference of 0.2~0.3 eV. This result provides a valuable guideline for the molecular designfor efﬁcient organic solar cells.

The charge generation efﬁciency is plotted against the energetic difference between
the singlet excited state and charge-transfer state.

We w o r k o n t h e d e v e l o p m e n t o f n e w o r g a n i c
semiconducting polymer materials and theirapplication to organic electronic devices. Speciﬁcally,
relying on the basic chemistry of the intermolecularinteractions during the ﬁlm forming process from thesolutions, we seek the methodology and the molecular
design to control the precise structures in molecularand nano-scale at our will, and try to ﬁnd
breakthroughs to drastically enhance the performanceof the organic electronic devices. Targets of ourresearch are not only the conventional organic solar
cells and ﬁeld-effect transistors, but also the organic
electronic devices with new functions based on the
structure controls.

Publications
1. K. Nakano, Y. Kaji, and K. Tajima, “Impact of Narrowing Density of States in Semiconducting Polymers on
Performance of Organic Field-Effect Transistors”, small, 202205570 (2022).
2. F. Chen, K. Nakano, Y. Kaji, and K. Tajima, “Design of planar-zigzag semiconducting polymers to control
chain orientation and electronic structure for organic photovoltaics”, Materials Chemistry Frontiers, 6,3062-3069 (2022).
3. W.-C. Wang, K. Nakano, D. Hashizume, C.-S. Hsu, and K. Tajima, “Tuning Molecular Conformations toEnhance Spontaneous Orientation Polarization in Organic Thin Films”, ACS Appl. Mater. Interface, 14, 16,
18773-18781 (2022).
4. C. Wang, H. Hao, and K. Tajima, “Essential Role of Triplet Diradical Character for Large Magnetoresistancein Quinoidal Organic Semiconductor with High Electron Mobility”, Adv. Sci., 2022, 9, 221045 (2022).
5. K. Nakano, F. Chen, Y. Kaji, and K. Tajima, “Control of molecular orientations by sequential deposition toenhance organic photovoltaic performance”, Mater. Chem. Phys., 281, 125849 (2022).

26

Core members(Research Scientist) Kyohei Nakano(Special Postdoctoral Researcher)
Chao Wang, Hitoshi Saito(Postdoctoral Researcher)
Yuto Ochiai, Takaho Yokoyama(RIKEN Student Researcher M) Ryo Suzuki

Emergent Bioengineering Materials
Research Team
Yoshihiro Ito (D.Eng.), Team Leader
y-ito@riken.jp
Research ﬁeld
Organic Chemistry, Materials Science, Bioengineering

Keywords
Energy conversion, Sensors, Precise polymer
synthesis, Molecular evolutionary engineering,
Nanobiotechnology

Brief resume
1987 D.Eng., Kyoto University
1988 Assistant Professor, Kyoto University

Multiple immune assay system using
microarray chip with a photo-reactive polymer
We developed a multiple microarray assay system for allergy diagnosis and it was listed
in Japanese medical insurance. Here a new rapid automatic quantitative diagnostic
system for multiple SARS-CoV-2 mutant protein-speciﬁc antibodies was developed using
the microarray with photoreactive polymers containing phenylazide and polyoxyethylene.
The polymers were coated on a plastic plate and aqueous solutions of mutant virus
proteins were microspotted on the coated plate and immobilized by photoirradiation.

1996 Associate Professor, Kyoto University
1997 Associate Professor, Nara Institute of Science andTechnology
1999 Professor, University of Tokushima
2001 Project Leader, Kanagawa Academy of Science andTechnology
2004 Chief Scientist, Nano Medical Engineering Laboratory,
RIKEN (-present)2013 Team Leader, Emergent Bioengineering Materials
Research Team, RIKEN Center for Emergent Matter
Science (-present)

OutlineVirus-speciﬁc IgG in the serum or blood was automatically assayed using an instrumentthat we developed for pipetting, reagent stirring, and washing. Blood collected from theﬁngertip (5 μL) and a test period of 8 min were sufﬁcient conditions for conducting multiple antibody assays. The results highly correlated with those of the conventional
enzyme-linked immunoassay or immunochromatography. The system facilitates rapid
and quantitative automatic assays and aid in the diagnosis of various viral infectious
diseases and assessment of the immune status for clinical applications.

Rapid and quantitative automatic detection of multiple antibodies against SARS-CoV-2
mutants using ﬁngertip blood

Publications
1. M. M. Rahman, M. Abosheasha, Y. Ito, and M. Ueda, “DNA-Induced Fusion between Lipid Domains of
Peptide-Lipid Hybrid Vesicles”, Chem. Commun., 58, 11799 (2022).
2. J. Akimoto, H. Kashiwagi, N. Morishima, S. Obuse, T. Isoshima, T. Kageyama, H. Nakajima, and Y. Ito,
“Rapid and quantitative detection of multiple antibodies against SARS-CoV-2 mutant proteins byphoto-immobilized microarray”, Anal. Sci., 38, 1313 (2022).
3. M. Othman, Y. Ito, and J. Akimoto, “Mild-temperature-induced recombination of crosslinking structure inhydrogel using phenylboronic-acid-functionalized 3D nanoparticle crosslinkers”, ACS Appl. Polym. Mater.,
4, 5047 (2022).
4. H. Kashiwagi, N. Morishima, S. Obuse, T. Isoshima, J. Akimoto, and Y. Ito, “SARS-CoV-2 proteins microarrayby photoimmobilization for serodiagnosis of the antibodies”, Bull. Chem. Soc. Jpn., 94, 2435 (2021).
5. S. Tada, X. Ren, H. Mao, Y. Heo, S.-H. Park, T. Isoshima, L. Zhu, X. Zhou, R. Ito, S. Kurata, M. Osaki, E.
Kobatake, and Y. Ito, “Versatile mitogenic and differentiation-inducible layer formation by underwater
adhesive polypeptides”, Adv. Sci., 2100961 (2021).

Advanced materials composed of biological and artiﬁcial
components are synthesized for development ofenvironmentally friendly energy collection and conversion
systems. By combination of organic synthetic chemistry,
polymer chemistry, and biotechnology, novel synthesis
method will be established and materials using biologicaland artiﬁcial elements will be achieved by their chemical
fabrication, and the characterization of the interfaces
between biological and artiﬁcial elements for highly
efﬁcient energy collection and conversion. Especially ourteam will establish a new methodology, a chemicallyextended molecular evolutionary engineering as an“Emergent Chemistry” to create a speciﬁc allyfunctionalized polymer by screening of random
sequence of polymer library containing functionalmonomers.

Core members(Senior Research Scientist)
Masuki Kawamoto, Takanori Uzawa, Motoki Ueda
(Postdoctoral Researcher)
Mohammed Abdelhamid ramadan Abosheasha(Senior Visiting Scientist) Hiroshi Abe(Visiting Scientist) Kyoji Hagiwara, Jun Akimoto(International Program Associate)
Ramadan Mohamed Mohamed Osama Metawea(Junior Research Associate) Minxing Hu(Technical Staff) Noriko Minagawa, Hideaki Takaku(Trainee) Kon Son

27

Supramolecular Chemistry Division

Emergent Supramolecular Materials
Research Team
Yong-Jin Pu (D.Eng.), Team Leader
yongjin.pu@riken.jp
Research ﬁeld
Chemistry, Materials Science

Keywords
Excited State, Interstate Transition, Organic
Semiconductor, Semiconductor Nanoparticle,
Colloidal Quantum Dot

Brief resume
2002 D. Eng., Waseda University
2002 Research associate, Waseda University

Simple cubic self-assembly of
colloidal quantum dots

2004 JSPS Postdoctoral Fellowship for Research Abroad(University of Oxford)
2006 Research associate, Yamagata University
2010 Associate Professor, Yamagata University

Colloidal quantum dots (QDs) have attracted substantial attention due to their characteristic optoelectronic properties based on their size conﬁnement effects. They are also
known to form highly ordered superlattices in the self-assembled solid state. The geometry of such self-assembled QDs has been explored theoretically and experimentally in2013 PRESTO Researcher, Japan Science and Technology
Agency2017 Team Leader, Emergent Supramolecular Materials
Research Team, Supramolecular Chemistry Division,
RIKEN Center for Emergent Matter Science (-present)

order to better understand the ensemble effects on their optical and electrical properties,
especially with regard to solid-state device applications. We achieved the selective control

Outlineof the geometry of colloidal quasi-spherical PbS QDs in highly-ordered two and three
dimensional superlattices: Disordered, simple cubic (sc), and face-centered cubic (fcc).
Gel permeation chromatography (GPC), not based on size-exclusion effects, was developed to quantitatively and continuously control the ligand coverage of PbS QDs. This
selective formation of different geometric superlattices based on GPC promises applications of such colloidal quasi-spherical QDs in high-performance optoelectronic devices.

We precisely control the energy levels, interstatet r a n s i t i o n r a t e , l u m i n e s c e n c e e fﬁ c i e n c y , s p i nmultiplicity etc. of organic/inorganic semiconductors
and nanoparticles by their dynamic and static
molecular structure, shape/size, chemicalcomposition, and assembly pattern, for creating
innovative energy-related technologies.

Core members

3D self-assembly supercrystals of PbS colloidal quantum dots with simple cubic (sc) structure

Publications
1. N. Aizawa, Y.-J. Pu, Y. Harabuchi, A. Nihonyanagi, R. Ibuka, H. Inuzuka, B. Dhara, Y. Koyama, K.
Nakayama, S. Maeda, F. Araoka, D. Miyajima, “Delayed ﬂuorescence from inverted singlet and triplet
excited states”, Nature, 609, 502 (2022).
2. J. Liu, K. Enomoto, K. Takeda, D. Inoue, Y.-J. Pu, “Simple Cubic Self-Assembly of PbS Quantum Dots byFinely Controlled Ligand Removal through Gel Permeation Chromatography”, Chem. Sci., 12, 10354(2021).
3. T. Lee, K. Enomoto, K. Ohshiro, D. Inoue, T. Kikitsu, H.-D. Kim, Y.-J. Pu, D. Kim, “Controlling the Dimensionof the Quantum Resonance in CdTe Quantum Dot Superlattices Fabricated via Layer-by-Layer Assembly”,
Nat. Commun., 11, 5471 (2020).
4. N. Aizawa, Y. Harabuchi, S. Maeda, Y.-J. Pu, “Kinetic Prediction of Reverse Intersystem Crossing in
Organic Donor–Acceptor Molecules”, Nat. Commun., 11, 3909 (2020).
5. K. Enomoto, D. Inoue, Y.-J. Pu, “Controllable 1D patterned assembly of colloidal quantum dots on PbSO4
nanoribbons”, Adv. Funct. Mater., 29, 1905175 (2019).

28(Research Scientist)
Kazushi Enomoto, Ryutaro Komatsu(Special Postdoctoral Researcher) Retno Miranti

Physicochemical Soft Matter Research Team
Fumito Araoka (D.Eng.), Team Leader
fumito.araoka@riken.jp
Research ﬁeld
Physical and Structural Properties ofFunctional Organic Materials

Keywords
Liquid crystals, Polymeric materials, Soft-matterphysics, Optical properties, Organic nonlinear optics,
Organic ferroelectrics

Brief resume

Topology-dependent lehmann rotationin chiral nematic emulsions
Lehmann rotation is a ‘heat ﬂow’ -to- ‘motion’ energy conversion effect in liquid

2003 Ph.D. in Engineering, Tokyo Institute of Technology,
Japan
2003 Postdoctoral Researcher, Catholic University of Leuven,
Belgium
2005 Postdoctoral Researcher, The University of Tokyo
2006 Postdoctoral Researcher, Tokyo Institute of Technology

crystals, which was found in the end of the 19th century. In spite of the huge effort by2007 Assistant Professor, Tokyo Institute of Technology

physicists for more than 100 years, its physical mechanism has not been clear yet. On the2013 Unit Leader, Physicochemical Soft-Matter Research Unit,
Cross-Divisional Materials Research Program, RIKEN
Center for Emergent Matter Scienceother hand, topology is ubiquitous in liquid crystals which can be treated as continua tounderstand many other complex physical systems. In this research, it was proven thathighly efﬁcient Lehmann rotation is realizable even in emulsion states of a chiral liquid2018 Team Leader, Physicochemical Soft-Matter Research
Team, RIKEN Center for Emergent Matter Science(-present)

crystal dispersed in a ﬂuorinated oligomer, in which topological diversity is conﬁrmed
depending on the droplet size and the strength of chirality. Interestingly, the estimatedheat-rotation conversion rate therein signiﬁcantly depends on these inner topological

Outlinestates of the droplets. This result is not merely important as a key to solve thelong-persistent physical problem in Lehmann rotation, but also interesting for fundamental
sciences related to topology.

(A) Topological diversity in a chiral nematic emulsion, (B) Lehmannrotation depending on the topological states.

Publications

Publications
1. H. Nishikawa, K. Sano and F. Araoka, “Anisotropic ﬂuid with phototunable dielectric permittivity”, Nat.
Commun., 13, 1142 (2022).

Our team is mainly working on functionality ofsoft-matter systems from the viewpoints of physicalexperiments and analyses. In our research unit,
particular attention is paid to liquid crystals due to theirself-organizability leading to multifarious structures inwhich many interesting physical phenomena emerge.
Our interest also covers potential applications of suchsoft-matter systems towards optical/electronic or
chemical devices. For example, 1. Ferroelectricinteractions and switching mechanisms in novel liquid
crystalline ferroelectric materials, 2. Chirality related
phenomena - origin and control of emergence, as wella s a p p l i c a t i o n s o f s u p e r s t r u c t u re c h i r a l i t y i n
self-organized soft-matter systems, 3. Novel
optical/electronic devices based on self-organizedsoft-matter systems.

2. H. Nishikawa and F. Araoka, “A New Class of Chiral Nematic Phase with Helical Polar Order”, Adv. Mater.,
33, 2101305 (2021).

Core members

3. S. Aya and F. Araoka, “Kinetics of motile solitons in nematic liquid crystals”, Nat. Commun., 11, 3248
(2020).

(Special Postdoctoral Researcher) Hiroya Nishikawa(Postdoctoral Researcher) Taishi Noma, Daichi Okada

4. J. Yoshioka and F. Araoka, “Topology-dependent self-structure mediation and efﬁcient energy conversion
in heat-ﬂux-driven rotors of cholesteric droplets”, Nat. Commun., 9, 432 (2018).
5. K. V. Le, H. Takezoe, and F. Araoka, “Chiral Superstructure Mesophases of Achiral Bent-Shaped Molecules– Hierarchical Chirality Ampliﬁcation and Physical Properties”, Adv. Mater., 29, 1602737 (2017).

29

Supramolecular Chemistry Division

Materials Characterization Support Team
Daisuke Hashizume (D.Sci.), Team Leader
hashi@riken.jp
Research ﬁeld
Structural Chemistry, Analytical Chemistry,
Materials Science

Keywords
X-ray crystal structure analysis, Electron microscopy,
Chemical analysis

Brief resume
1997 Tokyo Institute of Technology, PhD in Chemistry

Visualization of chemical bondsby accurate X-ray analysis
Our team has investigated the nature of molecules, which have unusual chemicalbonds and show less stability, in the crystalline state by analyzing the distribution ofvalence electrons derived from accurate and precise single-crystal X-ray crystal structure
analysis.
The conventional X-ray diffraction method clariﬁes the arrangement of atoms in the
crystalline state by modeling total electron density distribution using spherical atom
(isolated atom) models. As widely recognized, the resulted structures give important

1997 Research Associate, Department of Applied Physics andChemistry, Univ. of Electro-Communications
2002 Research Scientist, Molecular Characterization Team,
Advanced Development and Support Center, RIKEN
2011 Senior Research Scientist, Materials Characterization
Team, Advanced Technology Support Division, RIKEN
2013 Unit Leader, Materials Characterization Support Unit,
Supramolecular Chemistry Division, RIKEN Center for
Emergent Matter Science
2018 Team Leader, Materials Characterization Support Team,Supramolecular Chemistry Division, RIKEN Center for
Emergent Matter Science (-present)

Outlineinformation on the nature of molecules. However, valence density distribution, which playsa critical role in the chemistry of molecules, is not included in the resulted models. For
deeply understanding of the nature and chemistry of the analyzed molecule, in particular,
reactivity, charge separation, bonding mode, and intermolecular interaction, the valence
densities should be analyzed. In this study, the valence densities are analyzed by applying
multipole models instead of the spherical atom models to gain much direct information on
the electronic structure of molecules.

Distribution of 3d-electrons in Ni(II) complex and bonding electrons
Licensed under CC BY 4.0.

Publications
1. D. He, H. Ooka, Y. Li, Y. Kim, A. Yamaguchi, K. Adachi, D. Hashizume, N. Yoshida, S. Toyoda, S. H. Kim,and R. Nakamura, “Regulation of the electrocatalytic nitrogen cycle based on sequential proton-electrontransfer”, Nat. Catal., 5, 798 (2022).
2. T. Kubo, Y. Suga, D. Hashizume, H. Suzuki, T. Miyamoto, H. Okamoto, R. Kishi, and M. Nakano, “Longcarbon-carbon bonding beyond 2 Å in tris(9-ﬂuorenylidene)methane”, J. Am. Chem. Soc., 143, 14360(2021).
3. T. Kajitani, K. Motokawa, A. Kosaka, Y. Shoji, R. Haruki, D. Hashizume, T. Hikima, M. Takata, K. Yazawa,
K. Morishima, M. Shibayama, and T. Fukushima, “Chiral crystal-like droplets displaying unidirectionalrotating sliding”, Nat. Mater., 18, 266 (2019).
4. S. Park, S. W. Heo, W. Lee, D. Inoue, Z. Jiang, K. Yu, H. Jinno, D. Hashizume, M. Sekino, T. Yokota, K.
Fukuda, K. Tajima, and T. Someya, “Self-powered ultra-ﬂexible electronics via nano-grating-patternedorganic photovoltaics”, Nature, 561, 516 (2018).
5. Y. Sohtome, G. Nakamura, A. Muranaka, D. Hashizume, S. Lectard, T. Tsuchimoto, M. Uchiyama, and M.
Sodeoka, “Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2]cycloaddition”, Nat. Commun., 8, 14875 (2017).

30

Our team provides research support by means of
X-ray diffractometry, electron microscopy, andelemental analysis. In addition to supporting theindividual method, we propose multifaceted researchsupport by combining these methods. To keep our
support at the highest quality in the world, we always
update our knowledge and make training in our skills.
We make tight and deep collaboration withresearchers to achieve their scientiﬁc purposes and to
propose new insights into the research from ananalytical point of view, in addition to providing routine
analysis. Furthermore, we explore and develop new
measurement methods directed to more advanced
and sophisticated analyses.

Core members(Senior Technical Scientist) Keiko Suzuki(Expert Technician) Daishi Inoue(Technical Staff) Kiyohiro AdachiQuantum Information Electronics Division

Quantum Functional System Research Group
Seigo Tarucha (D.Eng.), Group Director
tarucha@riken.jp
Research ﬁeld
Physics, Engineering

Keywords
Quantum information devices, Quantum
entanglement, Quantum coherence, Topologicalparticles

Brief resume
1978 Staff member at the Basic Research Laboratories of
Nippon Tel. & Tel. Corp.

High-ﬁdelity universal quantum gate set
using electron spin qubits in silicon
One of the conditions that a fault-tolerant quantum computer requires to satisfy is
ﬁdelity of universal quantum gate set above 99%. In silicon spin qubits, the single-qubit
gate ﬁdelity exceeding 99.9% was demonstrated. In contrast, the two-qubit gate ﬁdelity
was limited to 98% due to a slow operation compared to spin dephasing. Here weovercome this problem and achieve the two-qubit gate ﬁdelity of 99.5% by making fasterthe gate speed by an order of magnitude than before.
We fabricated a silicon quantum dot device in an isotopically enriched silicon quantum
well/silicon germanium heterostructure with a micromagnet on top, which enables
high-speed single-qubit rotation by an electric-dipole spin resonance under a magnetic ﬁeld.

1990 Leader, Research Program on Electron Transport in
Low-Dimensional Semiconductor Structures, NTT Basic
Research Laboratories(-1998)
1998 Professor, Department of Physics, University of Tokyo
2004 Professor, Department of Applied Physics, University ofTokyo (-present)2013 Group Director, Quantum Functional System ResearchGroup, Quantum Information Electronics Division, RIKEN
Center for Emergent Matter Science (-present)2018 Deputy Director, RIKEN Center for Emergent Matter
Science2020 Team Leader, Semiconductor Quantum Information
Device Research Team, RIKEN Center for Emergent
Matter Science (-present)

OutlineWe used the fast spin rotation and a large exchange coupling to realize a fast CNOT
gate, the most important two-qubit gates, and achieved the single-qubit gate ﬁdelity of
99.8% and the two-qubit gate ﬁdelity of 99.5%.
The result shows that silicon spin qubits can compete with the most advanced qubit
systems of superconductor qubits and ion trap qubits.

Figure (Left) Silicon quantum bit device used for the experiment.
(Right) Characterization of the two qubit gate ﬁdelity using randomized benchmark method.

Publications

Quantum information processing is an ideal information
technology whose operation accompanies low-energy
dissipation and high information security. We aim atdemonstrating the ability of the solid-state information
processing, and ﬁnally paving the way for the realization
with innovative concepts and technology. The speciﬁc
research targets are implementation of small-scalequantum processing circuits with spins in silicon,development of control methods of quantum coherence
and entanglement in the circuits, and development ofinnovative quantum information devices, and in addition
development of control methods of topological particles
providing new concepts of quantum information.

1. K. Takeda, A. Noiri, T. Nakajima, T. Kobayashi, and S. Tarucha, “Quantum error correction with silicon spin
qubits”, Nature 608, 682-686 (2022).

Core members

2. A. Noiri, K. Takeda, T. Nakajima, T. Kobayashi, A. Sammak, G. Scappucci, and S. Tarucha, “Fast universal
quantum gate above the fault-tolerance threshold in silicon”, Nature 601, 338 (2022).

(Senior Research Scientist) Takashi Nakajima(Research Scientist) Kenta Takeda, Sadashige Matsuo(Special Postdoctoral Researcher) Akito Noiri(Visiting Researcher) Leon Camenzind

3. S. Matsuo, J.S. Lee, C.Y. Chang, Y. Sato, K. Ueda, C.J. Palmstrom, Christopher, and S. Tarucha,“Observation of nonlocal Josephson effect on double InAs nanowires”, Commun. Phys. 5, 221 (2022).
4. K. Kuroyama, S. Matsuo, Jo Muramoto, S. Yabunaka, S.R. Valentin, A. Ludwig, A.D. Wieck, Y. Tokura, and
S. Tarucha, “Real-time observation of charge-spin cooperative dynamics driven by a nonequilibrium
phonon environment”, Phys. Rev. Lett. 129, 095901 (2022)
5. T. Nakajima, A. Noiri, K. Kawasaki, J. Yoneda, P. Stano, S. Amaha, T. Otsuka, K. Takeda, M.R. Delbecq,
G. Allison, A. Ludwig, A. D. Wieck, D. Loss, and S. Tarucha, “Coherence of a driven electron spin qubit
actively decoupled from quasi-static noise”, Phys. Rev. X 10, 011060 (2020).

31Quantum Information Electronics Division

Quantum Condensate Research Team
Masahito Ueda (Ph.D.), Team Leader
masahito.ueda@riken.jp
Research ﬁeld
Physics, Engineering, Mathematics, Multidisciplinary

Keywords
Cold atoms, Bose-Einstein condensates, Quantum
simulation, Quantum thermodynamics, Explainable AI

Brief resume
1988 Resercher, NTT Basic Research Laboratories
1994 Associate Professor, Hiroshima University

Topological excitations in
Bose-Einstein condensates2000 Professor, Tokyo Institute of Technology
2008 Professor, University of Tokyo (-present)2014 Team Leader, Quantum Condensate Research Team,
Quantum Information Electronics Division, RIKEN Center
for Emergent Matter Science (-present)

Bose-Einstein condensates offer a cornucopia of symmetry breaking because a richvariety of internal degrees of freedom are available depending on the atomic species. We

Outlinehave used these degrees of freedom to explore various aspects of symmetry breaking
and topological excitations. Among them are the so-called Kibble-Zurek mechanism inwhich the order parameter develops singularities after some parameter of the system issuddenly quenched. Ordinary vortices and spin vortices are found to emerge. We also
investigate novel topological phenomena such as knot excitations in an antiferromagnetic
Bose-Einstein condensate.

We aim to explore physics frontiers that lie at theboarderlines between quantum physics, measurement, information, machine learning, and thermodynamics. In particular, we explore novel phenomena inultracold atoms which offer a versatile tool to investigate universal quantum phenomena that are independent of material-speciﬁc parameters. We also aim toconstract an explainable AI based on physics principles.

Core members(Research Scientist) Takashi Mori
(Postdoctoral Researcher) Lennart Justin Dabelow
Ground-state phase diagram of a spin-2 Bose-Einstein condensate (BEC).
Depending on the phase, different topological excitations appear.

Publications
1. L. Dabelow and M. Ueda, Three learning stages and accuracy-efﬁciency tradeoff of restricted Boltzmann
machines, Nat. Commun. 13, 5474 (2022)
2. E. Yukawa and M. Ueda, “Mophological Superﬂuid in a Nonmagnetic Spin-2 Bose-Einstein Condensate”,
Phys. Rev. Lett., 124, 105301 (2020).
3. K. Kawabata, K. Shiozaki, M. Ueda and M. Sato, “Symmetry and Topology in Non-Hermitian Physics”,
Phys. Rev. X, 9, 041015 (2019).
4. K. Kawabata, S. Higashikawa, Z. Gong, Y. Ashida, and M. Ueda, “Topological uniﬁcation of time-reversal
and particle-hole symmetries in non-Hermitian physics”, Nat. Commun., 10, 297 (2019). [selected as
Editors' Highlights]
5. Z. Gong, Y. Ashida, K. Kawabata, K. Takasan, S. Higashikawa, and M. Ueda, “Topological Phases of
Non-Hermitian Systems”, Phys. Rev. X, 8, 031079 (2018). [Viewpoint was published in “Miguel A. Bandresand Mordechai Segev, Physics, 11, 96 (2018)” ]32

Emergent Phenomena Observation Technology
Research Team
Daisuke Shindo (D.Eng), Team Leader
daisuke.shindo@riken.jp
Research ﬁeld
Physics, Engineering, Materials Science

Keywords
Imaging, Electron microscopy, Lorentz microscopy,
Flux quantum, Electron holography, Nanomagnetism

Brief resume
1982 D. Eng., Tohoku University
1982 Research Associate, Institute for Materials Research at
Tohoku University

In situ observation of accumulation andcollective motion of electrons

1992 Associate Professor, Institute for Advanced Materials
Processing at Tohoku University
1994 Professor, Institute of Multidisciplinary Research for
Advanced Materials at Tohoku University

Comprehensive understanding of electromagnetic ﬁelds requires their visualization both2010 Visiting Scientist, Quantum Phenomena Observation
Technology Team, RIKEN

inside and outside of materials. Since electromagnetic ﬁelds originate from various

2012 Team Leader, Emergent Phenomena Observation
Technology Research Team, RIKEN

motions of electrons, comprehensive study of motions of electrons is of vital importanceas well as of signiﬁcant interest for understanding various emergent phenomena. The
purpose of this study is to extend electron holography technology to visualize motions ofelectrons. By detecting electric ﬁeld variations through amplitude reconstruction2013 Team Leader, Emergent Phenomena Observation
Technology Research Team, Quantum Information
Electronics Division, RIKEN Center for Emergent Matter
Science (-present)
2019 Professor Emeritus, Tohoku University (-present)

processes for holograms, we have succeeded in visualizing collective motions ofelectrons around various insulating materials. The lower right ﬁgures below show one ofOutlineour experimental results of visualization of the collective motions of electrons aroundmicroﬁbrils of sciatic nerve tissue. In these reconstructed amplitude images, the brightyellow regions indicate the area where electric ﬁeld ﬂuctuates due to the motions ofelectrons. At the initial state (top ﬁgure),the electric ﬁeld variations are not prominent.
When the electron irradiation continues, however, bright yellow regions appear and theposition of the regions changes gradually between the two branches as indicated byblack arrows in the lower ﬁgures.
T h e s e re s u l t s i n d i c a t e t h a t t h ecollective motions of electrons canbe detected through electric ﬁeld
variation and can be visualized
through amplitude reconstruction
process for holograms.
Reconstructed amplitude images aroundmicroﬁbrils of sciatic nerve tissue (green).The
bright yellow regions indicate the area
where electric ﬁeld ﬂuctuates due tomotions of electrons.

Publications
1. K. Niitsu, Y. Liu, A. C. Booth, X. Yu, N. Mathur, M. J. Stolt, D. Shindo, S. Jin, J. Zang, N. Nagaosa and Y.
Tokura “Geometrically stabilized skyrmionic vortex in FeGe tetrahedral nanoparticles”, Nat. Mater., 21,305(2022).
2. H. Idzuchi, F.Pientka, K.-F. Huang, K. Harada, Ö. Gül, Y. J. Shin, L. T. Nguyen,N.H.Jo,D. Shindo, R. J.
Cava, P. C. Canﬁeld, and P. Kim,“Unconventional supercurrent phase in Ising superconductor Josephson
junction with atomically thin magnetic insulator”, Nat. Commun.,12, 5332,1 (2021).
3. D. Shindo, Z. Akase “Direct observation of electric and magnetic ﬁelds of functional materials”, Materials
Science and Engineering: R., 142, 100564,1 (2020).
4. D. Shindo, T. Tanigaki, and H. S. Park, “Advanced electron holography applied to electromagnetic ﬁeld
study in materials science”, Adv. Mater., 29,1602216,1 (2017).

For observing and analyzing emergent matterphenomena, we use advanced electron microscopy,
especially electron holography. Electron holography isa leading-edge observation technology that utilizes
interference effects of electron waves and visualizes
electromagnetic ﬁelds on the nanometer scale. Bydeveloping multifunctional transmission electron
microscope-specimen holders equipped with pluralprobes, changes in the electromagnetic ﬁelds in andaround specimens under applied voltages andmagnetic ﬁelds are quantitatively investigated. By
improving resolutions and precisions of theseobservation technologies, we can extensively study
mechanisms of emergent matter phenomena in newly
designed specimens for investigating many-bodysystems with multiple degrees of freedom.

Core members(Senior Research Scientist) Ken Harada(Technical Scientist) Yoh Iwasaki(Technical Staff) Keiko Shimada

5. M. Nakamura, F. Kagawa, T. Tanigaki, H. S. Park, T. Matsuda, D. Shindo, Y. Tokura, and M. Kawasaki,“Spontaneous polarization and bulk photovoltaic effect driven by polar discontinuity in LaFeO3/SrTiO3
heterojunctions”, Phys. Rev. Lett., 116(15), 156801,1 (2016).

33

Quantum Information Electronics Division

Quantum Nano-Scale Magnetism
Research Team
Yoshichika Otani (D.Sci.), Team Leader
yotani@riken.jp
Research ﬁeld
Physics, Engineering, Materials Science

Keywords
Nanomagnetism, Spintronics, Spin current, Spin Hall
effect, Edelstein effect, Magnon-phonon coupling

Brief resume
1989 D.Sci.,Department of Physics, Keio University
1989 Research Fellow, Trinity College University of Dublin,
IrelandTowards the new vision of Spintronics Devices:
Spin to charge conversion inducedby mechanical oscillation.
Spin conversion, the key concept of Spintronics, describes various intriguingspin-mediated interconversion phenomena at the nanoscale between electricity, light,
sound, vibration, and heat. The interaction between spin and mechanical oscillation
prevails not well explored among the above. Our group has demonstrated the feasibility ofa novel hybrid device's spin-mediated conversion of mechanical oscillation to electricalcharge current. Surface acoustic waves (SAWs) across ferromagnetic layers induce

1991 Postdoctoral Researcher, Laboratoire Louis Néel, CNRS,France1992 Research Instructor, Keio University
1995 Associate Professor, Tohoku University
2001 Team Leader, Quantum Nano-Scale Magnetics Team,
RIKEN
2004 Professor, ISSP University of Tokyo (-present)2013 Team Leader, Quantum Nano-Scale Magnetism
Research Team, Quantum Information Electronics
Division, RIKEN Center for Emergent Matter Science(-present)

Outlineperiodic elastic deformation that drives precession magnetization dynamics such as
ferromagnetic resonance (FMR), generating spin current ﬂow into adjacent nonmagnetic
layers. Interestingly, the coupling of SAWs with magnetic layers has more to offer. Our
g ro u p h a s a l s o d e m o n s t r a t e d t h e n o n re c i p ro c a l a t t e n u a t i o n o f S A W s v i amagneto-rotation coupling, a mechanism in which the magnetization couples to therotational lattice motion (see ﬁgure). The
achieved nonreciprocity values up to
100% opens up the route to application
developments such as magneto-acoustic
rectiﬁers. Beyond nonreciprocity, we arealso exploring the enhancements ofmagnon-phonon coupling towards thestrong coupling regime by using carefully
designed acoustic cavities.
Schematics of the magneto-rotation coupling. Depending on the propagation direction, SAWs rotate the lattice in
opposite directions (as indicted by the blue and red oriented cycles in the ﬁgure). This rotational lattice motion couples
with the magnetization via magnetic anisotropies, giving rise to a circularly polarized effective ﬁeld, which suppresses orenhances the magnetization precession (purple cone). In this way, it induces a nonreciprocal attenuation on the SAWs.

Publications
1. T. Yokouchi, S. Sugimoto, B. Rana, S. Seki, N. Ogawa, Y. Shiomi, S. Kasai, and Y. Otani, “Patternrecognition with neuromorphic computing using magnetic ﬁeld–induced dynamics of skyrmions”, Sci. Adv.
8, abq5652 (2022).
2. K. Kondou, M. Shiga, S. Sakamoto, H. Inuzuka, A. Nihonyanagi, F. Araoka, M. Kobayashi, S. Miwa, D.
Miyajima, and. Otani, “Chirality-induced magnetoresistance due to thermally driven spin polarization”,J.
Am. Chem. Soc. 144, 7302 (2022).
3. L. Liao, F. Xue, L. Han, J. Kim, R. Zhang, L. Li, J. Liu, X. Kou, C. Song, F. Pan, and Y. Otani, “Efﬁcient orbital
torque in poycrystalline ferromagnetic-metal/Ru/Al2O3 stacks:Theory and experiment”, Phys. Rev. B 105,
104434 (2022).
4. K. Kondou, H. Chen, T. Tomita, M. Ikhlas, T. Higo, A. H. MacDonald, S. Nakatsuji, and Y. Otani,“Giantﬁeld-like torque by the out-of-plane magnetic spin Hall effect in a topological antiferromagnet”, Nature
Commun. 12, 6491 (2021).
5. J. Kim, D Go, H. Tsai, D. Jo, K. Kondou, H-W Lee, and Y. Otani, “Nontrivial torque generation by orbital
angular momentum injection in ferromagnetic-metal/Cu/Al2O3 trilayers”, Phys. Rev. B 103, L020407 (2021).

34

The Quantum Nano-Scale Magnetism Team fabricatesferromagnetic/nonmagnetic hybrid nanostructuresfrom metals, semiconductors, insulators, andmolecules to study quantum behaviors in domain wall
displacement and magnetization dynamics mediatedby spin current, a ﬂow of spin angular momentum, andorbital current, a ﬂow of orbital angular momentum. We
focus our research on the fundamental process ofinterconversion and coupling between quasi-particles
such as electron spin, magnon, phonon, and photon. In
addition, we hope to develop a new technique forcontrolling spin conversion based on underlying
exchange and spin-orbit interactions and a new classof low-power spintronic devices for novel energy
harvesting.

Core members(Senior Research Scientist) Kouta Kondou(Research Scientist)
Junyeon Kim, Jorge Luis Puebla Nunez(Postdoctoral Researcher) You Ba(JRA / Student Trainee) Yunyoung Hwang(Student Trainee) Mingxing Wu, Liyang Liao

Quantum System Theory Research Team
Daniel Loss (Ph.D.), Team Leader
loss.daniel@riken.jp
Research ﬁeld
Theoretical Physics,
Quantum Theory of Condensed Matter

Keywords
Strongly correlated electron system, Nanodevice,Spin-orbit interaction, Topological quantum matter,
Majorana fermions and parafermions

Brief resume

Helical Liquids in Semiconductors
One-dimensional helical liquids can appear at boundaries of certain condensed mattersystems. Two prime examples are the edge of a quantum spin Hall insulator, also known

1985 Ph.D. in Theoretical Physics, University of Zurich,
Switzerland
1985 Postdoctoral Research Associate, University of Zurich,
Switzerland
1989 Postdoctoral Research Fellow, University of Illinois at
Urbana-Champaign, USA

as a two-dimensional topological insulator, and the hinge of a three-dimensional

1991 Research Scientist, IBM T. J. Watson Research Center,USA

second-order topological insulator. The presence of such states serves as a signature of

1993 Assistant Professor, Simon Fraser University, Canada

their nontrivial bulk topology.

1995 Associate Professor, Simon Fraser University, Canada

We investigate various aspects of helical liquids, such as their realization, topologicalprotection and stability, or possible experimental characterization. We focus especially on
proximity-induced topological superconductivity, allowing for exciting applications
towards topological quantum computation with the resulting Majorana bound states.

1996 Professor, Department of Physics, University of Basel,
Switzerland (-present)2012 Team Leader, Emergent Quantum System Research
Team, RIKEN
2013 Team Leader, Quantum System Theory Research Team,
Quantum Information Electronics Division, RIKEN Center
for Emergent Matter Science (-present)
2021 Team Leader, Semiconductor Quantum Information
Device Theory Research Team, RIKEN Center for
Quantum Computing (-present)

OutlineHelicity. (Left) In particle physics, the helicity of a particle is deﬁned through the relative orientation
between its spin and momentum. (Right) In a condensed matter system hosting spin-1/2 fermions
with quadratic dispersion, we can label the degenerate states near the Fermi level either by their spins
or by their helicities. Unlike the spin, the states with opposite helicities can be split in atime-reversal-invariant system.
Chen-Hsuan Hsu, Peter Stano, Jelena Klinovaja, and Daniel Loss, “Helical Liquids in Semiconductors”,
Semicond. Sci. Technol. 36, 123003 (2021).© IOP Publishing

Publications
1. O. Malkoc, P. Stano, D. Loss, “Charge-noise induced dephasing in silicon hole-spin qubits”, Phys. Rev.
Lett. 129, 247701 (2022).
2. Ch.-H. Hsu, P. Stano, J. Klinovaja, D. Loss, “Helical Liquids in Semiconductors”, Semicond. Sci. Technol.
36, 123003 (2021).
3. C.-H. Hsu, F. Ronetti, P. Stano, J. Klinovaja, and D. Loss, “Universal conductance dips and fractional
excitations in a two-subband quantum wire”, Phys. Rev. Research 2, 043208 (2020).
4. P. Aseev, P. Marra, P. Stano, J. Klinovaja, D. Loss, “Degeneracy lifting of Majorana bound states due toelectron-phonon interactions”, Phys. Rev. B, 99, 205435 (2019).
5. Ch.-H. Hsu, P. Stano, J. Klinovaja, D. Loss, “Majorana Kramers pairs in higher-order topological insulators”,
Phys. Rev. Lett., 121, 196801 (2018).

Our team works on the quantum theory of condensed
matter with a focus on spin and topologicalphenomena in semiconducting and magnetic
nanostructures. In particular, we investigate novel
mechanisms and seek new platforms hosting
topological or spin phases in solid-state systems,
including helical spin texture, topological insulators andtopological superconductors, which have potential
hosting topological quantum states, such as Majorana
fermions and parafermions. Moreover, we also
investigate (quasi-)one-dimensional Tomonaga-Luttinger
liquid, nuclear spins in semiconductors, many-bodyeffects in low-dimensional systems, (fractional)
quantum Hall effect, strongly correlated electron
systems, spin-orbit interaction, and quantum transportphenomena.

Core members(Senior Research Scientist) Peter Stano

35

Quantum Information Electronics Division

Spin Physics Theory Research TeamGen Tatara (D.Sci.), Team Leader
gen.tatara@riken.jp
Research ﬁeld
Physics, Engineering, Materials Science

Keywords
Spintronics, Spin-orbit interaction, Domain wall,
Monopole, Spin current, Metamaterial

Brief resume
1992 Doctor of Science, Department of Physics, Faculty of
Science, University of Tokyo

Microscopic theory of spintronics
Spin-charge conversion effects in spintronics have been conventionally argued based on
the concept of spin current, which has a fundamental ambiguity that cannot be avoided
arising from its non-conservation. We have presented a linear response theory formulation
to describe the effects in terms of response functions between physical observable, freefrom ambiguity. Our formalism without phenomenological constants like spin mixing
conductance is expected to be important for trustable predictions and designs of
spintronics devices.

1992 Postdoctoral Fellow, The Department of Physics, Facultyof Science, University of Tokyo
1994 Postdoctoral Fellow, The Institute of Physical andChemical Research, RIKEN
1996 Assistant Professor, Graduate School of Science, Osaka
University
2004 PRESTO, Japan Science and Technology Agency
2005 Associate Professor, Graduate School of Science andEngineering, Tokyo Metropolitan University
2012 Team Leader, Emergent Spintronics Theory Research
Team, RIKEN
2013 Team Leader, Spin Physics Theory Research Team,
Quantum Information Electronics Division, RIKEN Center
for Emergent Matter Science (-present)

Theoretical description of spintronics effects in analogy with electromagnetism has also
been carried out. The results would be useful for integration of spintronics into electronics.

In ferromagnetic metals, spin of electrons traveling through a magnetization structure follows the
local spin and acquires a quantum phase. This phase acts as an effective electromagnetic ﬁelds that
couples to electron spin.

OutlineOur aim is to explore novel spin-related effects withextremely high efﬁciency in condensed matters. We
thus contributes to development of spintronics, atechnology using spin as well as charge of electrons,
and to realization of ultrafast and high-density
information technology with low energy consumption.
Our particular interest is at present in a strong
quantum relativistic effect in solids, which is applicableto very strong magnets and efﬁcient conversion of spin
information to an electric signal. Our main method is aﬁeld theory.

Publications
Core members
1. H. Funaki, and G. Tatara, “Hydrodynamic theory of chiral angular momentum generation in metals”, Phys.
Rev. Research, 3, 023160(9) (2021).
2. G. Tatara, C. A. Akosa, and R. M. Otxoa de Zuazola, “Magnon pair emission from a relativistic domain wallin antiferromagnets”, Phys. Rev. Research, 2, 043226(17) (2020).
3. G. Tatara, “Effective gauge ﬁeld theory of spintronics”, Physica E: Low-dimensional Systems andNanostructures, 106, 208-238 (2019).
4. C. A. Akosa, O. A.Tretiakov, G. Tatara, and A. Manchon, “Theory of the Topological Spin Hall Effect in
Antiferromagnetic Skyrmions: Impact on Current-Induced Motion”, Phys. Rev. Lett., 121, 097204(5)(2018).
5. T. Kikuchi, T. Koretsune, R. Arita, and G. Tatara, “Dzyaloshinskii-Moriya Interaction as a Consequence of a
Doppler Shift due to Spin-Orbit-Induced Intrinsic Spin Current”, Phys. Rev. Lett.,116, 247201 (1-6) (2016).
(PRL Editors’Suggestion).

36(Postdoctoral Researcher) Guanxion Qu(Research Scientist)
Mohammad Hussein Naseef Al Assadi(Postdoctoral Researcher) Terufumi Yamaguti(Visiting Scientist) Collins Ashu Akosa

Quantum Effect Device Research Team
Koji Ishibashi (D.Eng.), Team Leader
kishiba@riken.jp
Research ﬁeld
Engineering, Physics

Keywords
Carbon nanotube, Semiconductor nanowire,
Quantum dots, Topological superconductor,
Quantum information devices

Brief resume
1988 D.Eng., Graduate School of Electrical Engineering,Osaka University

Towards Majorana qubit withsuperconductor/InAs nanowire
hybrid structures
To maintain quantum coherence is an essential requirement for the quantum computer.
But, it is really a tough requirement because of decoherence and noise that could easily
induce error in the computing processes. Majorana zeromodes (MZMs), simply
mentioned as Majorana fermion, could help to solve this difﬁculty as it is predicted to be

1988 Researcher, Frontier Research Program, RIKEN
1991 Researcher, Semiconductor Laboratory, RIKEN
1996 Visiting Researcher, Delft University of Technology, The
Netherlands
2003 Chief Scientist, Advanced Device Laboratory, RIKEN(-present)
2003 Adjunct Professor, Chiba University (-current)
2005 Adjunct Professor, Tokyo University of Science (-present)2013 Team Leader, Quantum Effect Device Research Team,
Quantum Information Electronics Division, RIKEN Center
for Emergent Matter Science (-present)robust against such local disturbance. Although Majorana fermion has not convincingly
been demonstrated, we are trying to search for it in the superconductor/semiconductor

Outlinenanowire and/or superconductor/topological insulator hybrid structures, in order to realize
the “Majorana qubit”. The ﬁgure shows a SNS (Super-Normal-Super) type Josephson
junction with a InAs nanowire grown by molecular beam epitaxy (MBE) technique followedby the in-situ deposition of the Al contacts. We are trying to measure the energy
spectrum of the MZMs by fabricating the RF-SQUID with the nanowire JJ and coupling itto the microwave resonator. This work has been carried out in collaboration with Prof.
Thomas Schäpers in Julich Research Center in Germany.

Scanning electron microscope image of the InAs nanowire Josephson junction with Al contacts

Publications
1. P. Zellekens, R. Deacon, P. Perla, D. Grützmacher, M. Lepsa, T. Schäpers, and K. Ishibashi, “Microwave
spectroscopy of Andreev states in InAs nanowire-based hybrid junctions using a ﬂip-chip layout”,
Commun. Phys., 5, 267 (2022).
2. M. Ohtomo, R. Deacon, M. Hosoda, N. Fushimi, H. Hosoi, M. Randle, M. Ohfuchi, K. Kawaguchi, K.
Ishibashi, S. Sato, “Josephson junctions of Weyl semimetal WTe2 induced by spontaneous nucleation of
PdTe superconductor”, Appl. Phys. Express 15, 075003 (2022).

We study quantum effects that appear in nanoscale
structures and apply them to functional nanodevice.
We focus on hybrid nanostructures, such as carbon
nanotube/molecule heterostructures and topologicalinsulator or nanostructures/superconductor hybridnanostructures as well as nanoscale Si transistors, tos t u d y q u a n t u m e ff e c t s a n d t o re a l i z e u n i q u efunctionalities that enable us to control electrons,
photons, excitons, and Cooper pairs on a single
quantum level. With those, we develop quantum
information devices and study physics behind them for
future low-power nanoelectronics.

Core members(Senior Research Scientist)
Keiji Ono, Russell S. Deacon(Special Post-Doctoral Researcher) Patrick Zellekens

3. A. Hida and K. Ishibashi, “Exciton Controlled-NOT Gate Using Coupled Quantum Dots in Carbon
Nanotube”, ACS Photonics, 9, 3398 (2022).
4. R. Wang, R. S. Deacon, J. Sun, J. Yao, C. M. Lieber, K. Ishibashi, “Gate Tunable Hole Charge Qubit
Formed in a Ge/Si Nanowire Double Quantum Dot Coupled to Microwave Photons”, Nano Lett. 19, 1052
(2019).
5. R. S. Deacon, J. Wiedenmann, E. Bocquillon, T. M. Klapwijk, P. Leubner, C. Brüne, S. Tarucha, K. Ishibashi,
H. Buhmann, L. W. Molenkamp, “Josephson radiation from gapless Andreev bound states in HgTe-based
topological junctions”, Phys. Rev. X, 7, 021011 (2017).

37

Quantum Information Electronics Division

Quantum Electron Device Research Team
Michihisa Yamamoto (D.Sci.), Team Leader
michihisa.yamamoto@riken.jp
Research ﬁeld
Physics, Engineering

Keywords
Two-dimensional electron systems, Single electron
manipulation, Nanodevices, Quantum coherence,
Quantum correlations

Brief resume
2004 Ph. D. in Physics, The University of Tokyo, Japan

Observation and control of
the Kondo screening cloud
The Kondo effect, an archetype of many-body correlations, arises from the interaction
between a localized spin and surrounding conducting electrons. Since conducting
electrons form a spin cloud to screen the localized spin, the Kondo state is also called as
the Kondo cloud. The size of the Kondo cloud is one of the most important parameters

2004 Research Associate, Department of Applied Physics,
The University of Tokyo
2014 Lecturer, Department of Applied Physics, The Universityof Tokyo2017 Associate Professor, Quantum-Phase Electronics Center,
School of Engineering, The University of Tokyo
2017 Unit Leader, Quantum Electron Device Research Unit,
RIKEN Center for Emergent Matter Science2020 Team Leader, Quantum Electron Device Research Team,RIKEN Center for Emergent Matter Science (-present)that determine properties of many-body states containing multiple localized spins.
We conﬁned a localized spin in a semiconductor artiﬁcial atom coupled to conducting

Outlineelectrons, embedded it into an electronic interferometer, and observed real shape of the
Kondo cloud. We found that its size is inverse proportional to the Kondo temperature andthat the cloud has the universal shape. More recently, we also found that the spin
screening state can be electrically controlled.
Our work is an important step towards
understanding of many-body correlated
states containing multiple magnetic
impurities and development of novel
quantum information devices based on thelong-range spin coupling. We are now
investigating systems, where multiple Kondo
clouds overlap with one another.
Schematic illustration of the device used for
detection of the Kondo cloud and real shape of
the Kondo cloud. The Kondo cloud shape wasobtained by quantifying the Kondo temperature
modulation by the gate voltage VQPC applied tothe quantum point contacts.
Figure taken from Nature 579, 210 (2020).

Publications

We develop quantum electron devices based on
manipulation and transfer of quantum degrees of
freedom in solids. We employ quantum electron
optics, where quantum states of propagating
electrons are manipulated in a single electron unit, andexperiments on transfer and manipulation of novel
quantum degrees of freedom in atomic-layer materials.
These experiments aim to reveal physics of quantum
coherence, quantum correlations, and quantum
conversions, as guiding principles for quantum
electron devices. We also employ state of the art
quantum technologies to solve long-standing
p ro b l e m s i n c o n d e n s e d m a t t e r p h y s i c s f ro m
microscopic points of view.

Publications

1. M. Tanaka, K. Watanabe, T. Taniguchi, K. Nomura, S. Tarucha, and M. Yamamoto, “Temperature-induced
phase transitions in the correlated quantum Hall state of bilayer graphene”, Phys. Rev. B, 105, 075427(2022).
2. R. Ito, S. Takada, A. Ludwig, A. D. Wieck, S. Tarucha, and M. Yamamoto, “Coherent beam splitting of ﬂying
electrons driven by a surface acoustic wave”, Phys. Rev. Lett., 126, 070501 (2021).
3. M. Tanaka, Y. Shimazaki, I. V. Borzenets, K. Watanabe, T. Taniguchi, S. Tarucha, and M. Yamamoto,“Charge Neutral Current Generation in a Spontaneous Quantum Hall Antiferromagnet”, Phys. Rev. Lett.,
126, 016801 (2021).
4. I. V. Borzenets, J. Shim, J. C. H. Chen, A. Ludwig, A. D. Wieck, S. Tarucha, H.-S. Sim, and M. Yamamoto,“Observation of the Kondo screening cloud”, Nature, 579, 210 (2020).
5. Y. Shimazaki, M. Yamamoto, I. V. Borzenets, K. Watanabe, T. Taniguchi, and S. Tarucha, “Generation anddetection of pure valley current by electrically induced Berry curvature in bilayer graphene”, Nat. Phys., 11,1032 (2015).

38

Core members(Research Scientist) Yuya Shimazaki(Postdoctoral Researcher)Ngoc Han Tu, David Pomaranski, Ryo ItoSemiconductor Science Research Support TeamFumihiro Matsukura (D.Sci.), Team Leader
fumihiro.matsukura@riken.jp
Research ﬁeld
Physics, Materials Science

Keywords
Nanometer-scale fabrication, Sample characterization,
Education of users

Brief resume
1994 Research Associate, RIEC, Tohoku University
2006 Associate Professor, RIEC, Tohoku University

Supporting researchers fornanometer-scale fabrication2012 Professor, AIMR, Tohoku University
2018 Professor, CIES, Tohoku University
2023 Team Leader, Semiconductor Science Research
Support Team, RIKEN Center for Emergent Matter
Science (-present)

To build a sustainable society with environment-device, it is essential to realize energyeffective devices and faster information processes. To realize such devices, theOutlineresearchers at the Center for Emergent Matter Science are enthusiastically pursuing todevelopment of quantum devices, spin devices and quantum computers. In building suchdevices, highly sophisticated equipment and support for keeping the best condition of theequipment are required.
Our team is established to support the researcher’ s activity by providing skillfulexpertise. We are responsible for the operation of equipment like lithography systems
including electron beam lithography systems, maskless UV photolithography systems,
deposition systems like evaporators and sputters, dry and wet etching systems andobservation system as scanning electron microscopy and for keeping them in the best
condition. We instruct users in the usage of equipment and provide technical informationin fabrication. With our effort, the researchers are now able to fabricate and characterizevarious devices in the range of 10 nm – 10 μm tirelessly.

Our mission is to develop novel technologies with awide range of applications in nanoscience andnanotechnology and to support the users in RIKEN for
nanometer-scale fabrication and the characterizationof specimens. We are responsible for the operation of
the facilities including the clean room and the chemicalrooms with suitable safety measures. The clean room
is for the fabrication and characterization of
nanometer-scale devices and the chemical rooms arefor those of wet samples for chemistry and biology. In
the clean room and the chemical rooms, more than 30
apparatus have been installed and are open to theusers. We are also responsible for the education of theusers.

Core members(Technical Staff)
Reiko Nakatomi, Yoshio Taguchi, Hideaki Oyama

Examples of the specimen fabricated in the clean room.

39

Cross-Divisional Materials Research Program

Emergent Molecular Assembly Research Unit
Hiroshi Sato (Ph.D.), Unit Leader
hiroshi.sato@riken.jp
Research ﬁeld
Chemistry, Materials Science

Keywords
Self-assembly, Crystal engineering, Porous materials,
Surface/Interface

Brief resume
2008 Ph. D., The University of Tokyo
2008 Researcher, JST-ERATO Kitagawas Integrated Pores
Project

Topological bonds assemble toform porous crystals
Our unit succeeded for the ﬁrst time in synthesizing crystals by precisely arranging
catenane molecules (topological bonds), which are chains of two ring-shaped molecules,
and metal ions three dimensionally through coordination bonds. The crystal structure was
examined using single crystal X-ray structural analysis, and it was found that more than
90% of the crystal is composed of catenane molecules, that it has a structure withmicropores, and that it changes its structure with changes in temperature. Furthermore, it
was revealed that the crystal changes its shape when force is applied from the outside
and recovers its original shape when the force is removed, showing rubber-like properties

2010 Project Assistant Professor, Institute for Integrated
Cell-Material Sciences, Kyoto University
2012 Assistant Professor, Institute for Integrated Cell-Material
Sciences, Kyoto University
2014 Lecturer, Department of Chemistry and Biotechnology,
University of Tokyo
2020 Associate Professor, Department of Chemistry andBiotechnology, University of Tokyo
2020 Researcher, PRESTO, Japan Science and Technology
Agency2021 Unit Leader, Emergent Molecular Assembly Research
Unit, Cross-Divisional Materials Research Program,
RIKEN Center for Emergent Matter Science (-present)
2023 Specially Appointed Professor, International Institute for
Sustainability with Knotted Chiral Meta Matter(-present)

despite its crystalline nature. This is expected to lead to the application of innovative
porous materials that can absorb and desorb gas molecules, such as carbon dioxide, by

Outlinepinching and releasing them with a ﬁnger.

The aim of this unit is to unleash the potential ofmolecules by controlling their assembly andarrangement patterns, and to create novel functions
that are impossible to achieve with single molecules.
Our speciﬁc research themes are as follows.
(1) Creation of materials by precise arrangement of
topological bonds: By periodically arranging topologicalbonds such as catenanes, we will realize new materials.
(2) Sequence control in supramolecular polymerization:
In supramolecular polymerization, it is still challenging tocontrol the monomer sequence, so we are trying tocontrol the sequence in coordination polymers.

Core members
An elastic porous crystal with a Densely Catenated Backbone

Publications
1. W. Meng, S. Kondo, T. Itoh, K. Komatsu, J. Pirillo, Y. Hijikata, Y. Ikuhara, T. Aida, and H. Sato “An Elastic
Metal–Organic Crystal with a Densely Catenated Backbone”, Nature, 598, 298 (2021).
2. H. Huang, H. Sato, J. Pirillo, Y. Hijikata, Y. S. Zhao, S. Z. D. Cheng, and T. Aida “Accumulated Lattice Strain
as an Internal Trigger for Spontaneous Pathway Selection”, J. Am. Chem. Soc., 143, 15319 (2021).
3. H. Sato, T. Matsui, Z. Chen, J. Pirillo, Y. Hijikata, and T. Aida “Photochemically Crushable and Regenerative
Metal–Organic Framework”, J. Am. Chem. Soc., 142, 14069 (2020).
4. J.-M. Lee and H. Sato “Photoswitching to the Core”, Nat. Chem., 12, 584 (2020).
5. S. Suginome, H. Sato, A. Hori, A. Mishima, Y. Harada, S. Kusaka, R. Matsuda, J. Pirillo, Y. Hijikata, and T.
Aida “One-Step Synthesis of an Adaptive Nanographene MOF: Adsorbed Gas-Dependent Geometrical
Diversity”, J. Am. Chem. Soc., 141, 15649 (2019).

40(Postdoctoral Researcher) Bohan Cheng(Special Postdoctoral Researcher) Saiya Fujiwara(Student Trainee) Kunyi Leng, Wei Yuan

Computational Materials Function Research Unit
Yong Xu (Ph.D.), Unit Leader
yong.xu＠riken.jp
Research ﬁeld
Condensed Matter Physics, Materials Science

Keywords
First-principles calculations, Topological quantum
matters, Thermoelectric effect, Thin ﬁlms andinterfaces, Theoretical materials design

Brief resume

Discovery of graphene’s latest cousin: stanene
One of the grand challenges in condensed matter physics and material science is todevelop room-temperature electron conduction without dissipation. Based on ﬁrst-principles calculations, we predicted a new material class of stanene (i.e., the latest cousin ofgraphene) that is promising for the purpose. Stanene (from the Latin stannum meaningtin) is a 2D layer of tin atoms in a buckled honeycomb lattice. One intriguing feature of2010 Ph.D., Condensed Matter Physics, Tsinghua University,
Beijing, China
2013 Alexander von Humboldt Fellow, Fritz Haber Institute,
Berlin, Germany
2015 Research Scholar, Stanford University, USA
2015 Assistant Professor, Tsinghua University, Beijing, China
2015 Unit Leader, Computational Materials Function Research
Unit, Cross-Divisional Materials Research Program,
RIKEN Center for Emergent Matter Science (-present)2018 Associate Professor, Tsinghua University, Beijing, China
2021 Professor, Tsinghua University, Beijing, China (-present)

stanene and its derivatives is that the materials support large-gap quantum spin Hall
(QSH) states, enabling conducting electricity without heat loss. Moreover, many otherexotic characteristics were also proposed theoretically for stanene-related materials,
including enhanced thermoelectric performance, topological superconductivity and thenear-room-temperature quantum anomalous Hall effect. Very recently we have success-Outlinefully fabricated the monolayer stanene structure by molecular beam epitaxy. This will stim-

We a re a re s e a rc h g ro u p o n t h e o re t i c a l a n dcomputational condensed-matter and materials
physics. Our main research interest is tounderstand/predict unusual quantum phenomena andnovel material properties, based on ﬁrst-principles
electronic structure calculations. In particular, we focus
on exploring the electronic, thermal, optical andmagnetic properties of low-dimensional systems (e.g.
layered materials, materials surfaces and interfaces) as
well as materials with non-trivial topological order. The
primary goal of our research is to design advanced
functional materials that can be used for
low-dissipation electronics, high-performance
thermoelectricity and high-efﬁciency solar cell. We arealso interested in developing theoretical methods forstudying quantum thermal, electronic, andthermoelectric transport at the mesoscopic scale.

ulate great experimental effort to observe the unusual electronic properties of stanene.

(a) An element familiar as thecoating for tin cans: tin(chemical symbol Sn).
(b) A 2D layer of tin, named
stanene, when decorated byhalogen atoms, is able toconduct electricity perfectly
along its edges (blue and red
arrows) at room temperature.
(c) The atomic structure model(top view) superimposed on
the measured STM images forthe 2D stanene on Bi2Te3(111).
(d) Side view.

Publications

Publications
1. H. Li, Z. Wang, N. Zou, M. Ye, R. Xu, X. Gong, W. Duan, and Y. Xu “Deep Neural Network Representationof Density Functional Theory Hamiltonian”, Nat. Comput. Sci., 2, 367 (2022).
2. Y. Li, J. Li, Y. Li, M. Ye, F. Zheng, Z. Zhang, J. Fu, W. Duan, and Y. Xu “High-Temperature Quantum Anomalous
Hall Insulators in Lithium-Decorated Iron-Based Superconductor Materials”, Phys. Rev. Lett., 125, 086401(2020).
3. C. Liu, Y. Wang, H. Li, Y. Wu, Y. Li, J. Li, K. He, Y. Xu, J. Zhang, and Y. Wang “Robust axion insulator andChern insulator phases in a two-dimensional antiferromagnetic topological insulator”, Nature Mater., 19,522 (2020).
4. J. Li, Y. Li, S. Du, Z. Wang, B.-L. Gu, S.-C. Zhang, K. He, W. Duan, and Y. Xu, “Intrinsic magnetic
topological insulators in van der Waals layered MnBi2Te4-family materials”, Sci. Adv. 5, eaaw5685 (2019).
5. C. Wang, B. Lian, X. Guo, J. Mao, Z. Zhang, D. Zhang, B.-L. Gu, Y. Xu, and W. Duan, “Type-II Ising
superconductivity in two-dimensional materials with spin-orbit coupling”, Phys. Rev. Lett. 123, 126402 (2019).

41

Cross-Divisional Materials Research Program

Low-Dimensional Transport Research Unit
Ding Zhang (Ph.D.), Unit Leader
ding.zhang@riken.jp
Research ﬁeld
Physics

Keywords
Condensed matter physics, High-temperature
superconductor, Josephson effect, Low dimensional
superconductors, Van der Waals epitaxy

Brief resume
2014 PhD in physics, Max Planck Institute for Solid State
Research, Stuttgart, Germany

Josephson tunneling in twisted
bilayer cuprates
S u p e rc o n d u c t i v i t y i s o n e o f t h e m a c ro s c o p i c q u a n t u m p h e n o m e n a . T h esuperconducting state can be described by quantum mechanical wave functions
categorized as s-, p-, d-wave, etc., similar to the wave functions of a hydrogen atom.
Conventional superconductors such as tin or aluminum host s-wave pairing symmetry,
and although it remains debatable, most researchers believe that copper oxides ared-wave superconductors instead. Theoretically, if two d-wave superconductors are2014 PhD in physics, University of Stuttgart, Stuttgart,
Germany
2014 Post-doctor, Tsinghua University, Beijing, China.
2016 Assistant Professor, Tsinghua University, Beijing, China.
2018 Associate Professor, Tsinghua University, Beijing, China(-present)
2021 Unit Leader, Low-Dimensional Transport Research Unit,
Cross-Divisional Materials Research Program, RIKEN
Center for Emergent Matter Science (-present)

Outlinestacked vertically, the Josephson coupling strength starts to change once one
superconductor is twisted against the other one. It monotonically drops to zero when therotation angle increases up to 45 degrees. By contrast, the s-wave superconductors
show constant Josephson coupling, irrespective of the rotation angles. Recently, we
successfully fabricated high-quality c-axis twisted Josephson junctions with accurate
control over the twist angle. Junctions at various twist angles all exhibit a single tunnelingbranch behavior, suggesting that only the ﬁrst half of a unit cell on both sides of thetwisted ﬂakes is involved in the Josephson tunneling process. Interestingly, we found thatwhen one cuprate ﬂake is rotated by 45° against the other, Josephson coupling still
exists, and the coupling strength of 45° and 0° are comparable. This behavior isconsistent with s-wave pairing symmetry.

Twisted cuprate bilayer.

Publications

Publications

1. M. Liao, Y. Zhu, S. Hu, R. Zhong, J. Schneeloch, G. Gu, D. Zhang, and Q.-K. Xue, “Little-Parks likeoscillations in lightly doped cuprate superconductors”, Nat. Commun., 13, 1316 (2022).
2. Y. Zhu, M. Liao, Q. Zhang, H.-Y. Xie, F. Meng, Y. Liu, Z. Bai, S. Ji, J. Zhang, K. Jiang, R. Zhong, J.
Schneeloch, G. Gu, L. Gu, X. Ma, D. Zhang, and Q.-K. Xue, “Presence of s-wave pairing in Josephson
junctions made of twisted ultrathin Bi2Sr2CaCu2O8+x ﬂakes”, Phys. Rev. X, 11, 031011 (2021).
3. M. Liao, H. Wang, Y. Zhu, R. Shang, M. Raﬁque, L. Yang, H. Zhang, D. Zhang, and Q.-K. Xue,
“Coexistence of resistance oscillations and the anomalous metal phase in a lithium intercalated TiSe2
superconductor”, Nat. Commun., 12, 5342 (2021).
4. J. Falson, Y. Xu, M. Liao, Y. Zang, K. Zhu, C. Wang, Z. Zhang, Ho. Liu, W. Duan, K. He, Ha. Liu, J. H. Smet,
D. Zhang, and Q.-K. Xue, “Type-II Ising pairing in few-layer stanene”, Science 367, 1454 (2020).
5. D. Zhang, J. Falson, S. Schmult, W. Dietsche, and J. H. Smet, “Quasi-particle tunneling across an exciton
condensate”, Phys. Rev. Lett. 124, 246801 (2020).

42

Our research unit studies a variety of low-dimensional
electronic systems that undergo Cooper pairing. We
aim at addressing some of the basic properties suchas the pairing mechanism and the pairing symmetry.
Furthermore, we look for novel quantum phenomena
in reduced dimensions under specially designed
conditions. The experimental knobs include stacking
van der Waals heterostructures, injecting
lithium/hydrogen/ﬂuoride ions, varying the magnetic
ﬁeld orientations at ultralow temperatures, andramping up the magnetic ﬁeld to an extremely highvalue. By collaborating closely with experimental andtheoretical experts in the ﬁeld, we hope to gain acomprehensive understanding of those exotic
phenomena.

Topological Quantum Phenomenon
Research Unit
Tian Liang (Ph.D.), Unit Leader
tian.liang@riken.jp
Research ﬁeld
Physics

Keywords
Condensed matter physics, Topological quantum
matters, Berry phase physics, Thermoelectric effect,
Strongly Correlated electron system

Brief resume
2016 Ph.D. in physics, Princeton University, USA

Berry curvature generation
detected by Nernst responses
in ferroelectric Weyl semimetal
The quest for non-magnetic Weyl semimetals with high tunability of phase hasremained a demanding challenge. As the symmetry-breaking control parameter, the ferro-

2016 Postdoctoral associate, Stanford University, USA
2018 Postdoctoral Researcher, Strong Correlation Quantum
Transport Research Team, RIKEN Center for Emergent
Matter Science
2021 Assistant Professor, Tsinghua University, China (-present)
2021 Unit Leader, Topological Quantum Phenomenon
Research Unit, Cross-Divisional Materials Research
Program, RIKEN Center for Emergent Matter Science(-present)

electric order can be steered to turn on/off the Weyl semimetals phase, adjust the band
structures around the Fermi level, and enlarge/shrink the momentum separation of Weyl

Outlinenodes which generate the Berry curvature as the emergent magnetic ﬁeld. Here, we

In our unit, we aim to investigate the intriguing physicalproperties in topological phases of matter and strongly
correlated electron system, through the researchbased on the condensed matter experiment. First,
from fundamental physics point of view, we pay
attention to the nontrivial geometrical properties of theband structure, and aim to measure the novel
electrical, thermal, and magnetic quantum effect on
the system. In addition, from application point of view,
we work on the design of high quality thermoelectricmaterial and devices with low dissipation. In order toachieve the above mentioned goals, we will
collaborate with the researchers all over the world andenhance the understanding of physics both from thefundamental and application aspects.

report the realization of a ferroelectric non-magnetic Weyl semimetal based on
indium-doped Pb1−xSnxTe alloy where the underlying inversion symmetry as well as mirror
symmetries are broken with the strength of ferroelectricity adjustable via tuning indium
doping level and Sn/Pb ratio. The transverse thermoelectric effect, i.e., Nernst effect, bothfor out-of-plane and in-plane magnetic-ﬁeld geometry, is exploited as a Berry-curvature-sensitive experimental probe to manifest the generation of Berry curvature via there-distribution of Weyl nodes under magnetic ﬁelds. The results demonstrate a clean
non-magnetic Weyl semimetal coupled with highly tunable ferroelectric order, providing an
ideal platform for manipulating the Weyl fermions in non-magnetic system.

The left panel shows the topological phase transition in the system of In-PbSnTe. Since the spatial
inversion symmetry is broken by ferroelectricity, a Weyl semimetal phase appears. The right panel
shows anomalous Hall and thermoelectric Hall effect, which originates from the Berry curvature
generated by the Weyl nodes.
Publications

Publications

1. CL. Zhang, T. Liang, Y. Kaneko, N. Nagaosa, Y. Tokura, “Giant Berry curvature dipole density in aferroelectric Weyl semimetal”, npj Quantum Materials, 7, 1-6 (2022).
2. C. Zhang, T. Liang, M. S. Bahramy, N. Ogawa, V. Kocsis, K. Ueda, Y. Kaneko, M. Kriener, and Y. Tokura“Berry curvature generation detected by Nernst responses in ferroelectric Weyl semimetal”, PNAS, 118,
e2111855118 (2021).
3. C. Zhang, T. Liang, N. Ogawa, Y. Kaneko, M. Kriener, T. Nakajima, Y. Taguchi, and Y. Tokura “Highly tunable
topological system based on PbTe-SnTe binary alloy”, Phys. Rev. Materials, 4, 091201 (2020).
4. J.J. He, T. Liang, Y. Tanaka, and N. Nagaosa “Platform of chiral Majorana edge modes and its quantum
transport phenomena”, Commun. Phys., 2, 149 (2019).
5. K. Yasuda, H. Yasuda, T. Liang, R. Yoshimi, A. Tsukazaki, K. Takahashi, N. Nagaosa, M. Kawasaki, Y.
Tokura, “Nonreciprocal charge transport at topological insulator/superconductor interface”, Nat. Commun.
10, 2734 (2019).

43

Cross-Divisional Materials Research Program

Emergent Spectroscopy Research Unit
Youtarou Takahashi (Ph.D.), Unit Leader
youtarou.takahashi@riken.jp
Research ﬁeld
Physics, Materials Science

Keywords
Strongly correlated electron system, Multiferroics,
Terahertz spectroscopy, Ultrafast spectroscopy,
Non-reciprocal effect

Brief resume
2007 Ph.D, The University of Tokyo

Magnetoelectric optical effect withelectromagnons in helimagnet
Helical spin orders exhibit the magnetically induced ferroelectricity, resulting in the2007 Researcher, Tokura Multiferroic Project, ERATO, Japan
Science and Technology Agency
2011 Lecturer, Quantum-Phase Electronics Center, School ofEngineering, The University of Tokyo
2014 Associate Professor, Quantum-Phase Electronics Center,
School of Engineering, The University of Tokyo

ferroelectric polarization, the helical spin orders possess the chirality; the right-handed2014 Unit Leader, Emergent Spectroscopy Research Unit,
Cross-Divisional Materials Research Program, RIKEN
Center for Emergent Matter Science(-present)

and left-handed spin habits are distinguished in terms of chirality. The strong

2016 Associate Professor, Quantum-Phase Electronics Center,
School of Engineering, The University of Tokyo (-present)

concept of multiferroics with strong magnetoelectric coupling. In addition to themagnetoelectric coupling generates the novel spin excitation referred to aselectromagnon, which is the magnon endowed with the electric activity, in terahertz
region. We clariﬁed that the strong magnetoelectric coupling of the electromagnon

Outlineresonance causes the nonreciprocal optical effect in general. We also demonstrated theelectric ﬁeld control of chirality by using the helical spin order with ferroelectricity andchirality. On the electromagnon resonance, the reversal of the natural optical activity,
which is most fundamental nature of chiral matter, is observed. The control of opticalactivity may lead to the novel chiral optics.

Control of natural optical activity induced by helical spin-orderPublications

Publications
1. Y. D. Kato, Y. Okamura, S. Minami, R. Fujimura, M. Mogi, R. Yoshimi, A. Tsukazaki, K. S. Takahashi, M.
Kawasaki, R. Arita, Y. Tokura and Y. Takahashi “Optical anomalous Hall effect enhanced by ﬂat bands inferromagnetic van der Waals semimetal”, npj Quantum Mater., 7, 73 (2022).
2. Y. Okamura, T. Morimoto, N. Ogawa, Y. Kaneko, G-Y. Guo, M. Kawasaki, N. Naogaosa, Y. Tokura, and Y.
Takahashi, “Photovoltaic effect by soft phonon excitation”, PNAS 119, e2122313119 (2022).
3. S. Iguchi, R. Masuda, S. Seki, Y. Tokura and Y. Takahashi, “Enhanced gyrotropic birefringence and natural
optical activity on electromagnon resonance in a helimagnet”, Nat. Commun. 12, 6674 (2021).
4. Y. Hayashi, Y. Okamura, N. Kanazawa, T. Yu, T. Koretsune, R. Arita, A. Tsukazaki, M. Ichikawa, M
Kawasaki, Y. Tokura and Y. Takahashi, “Magneto-optical spectroscopy on Weyl nodes for anomalous andtopological Hall effects in chiral MnGe”, Nat. Commun. 12, 5974 (2021).
5. R. Masuda, Y. Kaneko, Y. Tokura and Y. Takahashi, “Electric ﬁeld control of natural optical activity in a
multiferroic helimagnet”, Science 372, 496 (2021).

44

Light-matter interaction has been a fundamental issue
for the condensed matter physics. Optical spectroscopy plays an important role for the various researches,
and the emergent phenomena in condensed matterprovide novel optical responses. Our unit focuses on
the light-matter interaction on the strongly correlated
electron systems as listed below. (1) Magnetoelectric
optical effect driven by the cross-coupling between
the magnetism and dielectric properties in matter. (2)Optical control of the magnetism and dielectric properties. (3) Novel optical responses derived from the
topology in condensed matter. We are pushing
forward scientiﬁc and technological developments withthese researches.

Core members(Visiting Researcher) Yoshihiro Okamura

Emergent Functional Interface Research Unit
Masaki Nakano (Ph.D.), Unit Leader
mnakano@riken.jp
Research ﬁeld
Physics, Engineering, Chemistry, Materials Science

Keywords
Thin ﬁlms and interfaces, Electric-ﬁeld device,
Strongly-correlated oxide, 2D materials, Van der
Waals epitaxy

Brief resume
2009 Ph. D., Tohoku University

Emerging properties of van der Waals
superstructures
When conducting electrons in a solid are conﬁned within a two-dimensional plane, they
behave differently from those moving freely in a three-dimensional space. This is called
two-dimensional electron system, providing a unique platform in condensed matterphysics research, although available only in semiconductor heterostructures or inelectric-ﬁeld devices in the 1980s and the 1990s. After entering the 21st century,
however, the situation has been dramatically changed owing to the development of
epitaxial growth technique as well as the discoveries of different types of materials as
typiﬁed by graphene and topological insulators, and nowadays we can play with a variety
of 2D phenomena more easily than in the past. We are in particular interested in emerging
properties of 2D materials, and trying to build up functional interfaces from bottom-up
approach by van der Waals epitaxy. We have already established a route to layer-by-layer
epitaxial growth of various 2D materials, and now several research topics aiming for
discovery of intriguing interface phenomena are in progress.

2009 Postdoctoral Researcher, Institute for Materials
Research, Tohoku University
2009 Postdoctoral Researcher, Department of Condensed
Matter Physics, University of Geneva
2010 Postdoctoral Researcher, Correlated Electron ResearchGroup, RIKEN
2012 Research Associate, Department of Advanced Materials
Science, The University of Tokyo
2013 Research Associate, Institute for Materials Research,
Tohoku University
2014 Project Lecturer, Quantum-Phase Electronics Center,
The University of Tokyo
2019 Project Associate Professor, Quantum-Phase Electronics
Center, The University of Tokyo (-present)
2019 Unit Leader, Emergent Functional Interface Research
Unit, Cross-Divisional Materials Research Program,
RIKEN Center for Emergent Matter Science (-present)

OutlineWe explore physical properties and functionalities
emerging when materials are thinned down to monolayer limit. We in particular focus on monolayer properties of various 2D materials including hardly-cleavableand even metastable compounds that could be
realized by employing non-equilibrium epitaxial growthtechnique, and develop novel device functionalities incombination with electric-ﬁeld doping technique. In
addition, we construct van der Waals superstructuresby stacking different 2D materials aiming for discovery
of novel quantum phases emerging at the interfaces.

Van der Waals superstructures

Publications
Publications
1. Y. Wang, S. Kajihara, H. Matsuoka, B. K. Saika, K. Yamagami, Y. Takeda, H. Wadati, K. Ishizaka, Y. Iwasa,
and M. Nakano “Layer-number-independent two-dimensional ferromagnetism in Cr3Te4”, Nano Lett., 22,9964 (2022).
2. H. Matsuoka, T. Habe, Y. Iwasa, M. Koshino, and M. Nakano “Spontaneous spin-valley polarization in
NbSe2 at a van der Waals interface”, Nature Commun., 13, 5129 (2022).
3. N. Yoshikawa, H. Suganuma, H. Matsuoka, Y. Tanaka, P. Hemme, M. Cazayous, Y. Gallais, M. Nakano, Y.
Iwasa, and R. Shimano “Ultrafast switching to an insulating-like metastable state by amplitudon excitationof a charge density wave”, Nature Phys., 17, 909 (2021).
4. H. Matsuoka, S. E. Barnes, J. Ieda, S. Maekawa, M. S. Bahramy, B. K. Saika, Y. Takeda, H. Wadati, Y.
Wang, S. Yoshida, K. Ishizaka, Y. Iwasa, and M. Nakano “Spin-orbit-induced Ising ferromagnetism at a vander Waals Interface”, Nano Lett., 21, 1807 (2021).
5. M. Nakano, K. Shibuya, D. Okuyama, T. Hatano, S. Ono, M. Kawasaki, Y. Iwasa, and Y. Tokura “Collective
bulk carrier delocalization driven by electrostatic surface charge accumulation”, Nature, 487, 459 (2012).

45

Cross-Divisional Materials Research Program

Topological Quantum Matter Research Unit
Max Hirschberger (Ph.D.), Unit Leader
maximilian.hirschberger@riken.jp
Research ﬁeld
Physics, Materials Science

Keywords
Strongly Correlated electron system, Magnetism,
Skyrmion, Spin-orbit interaction, Emergent
electromagnetism, Topological materials, Frustrated
quantum magnets, Berry phase physics

Brief resume

Skyrmions in a centrosymmetric breathing
Kagome magnet
In hexagonal intermetallics Gd2PdSi3 and Gd3Ru4Al12, RKKY magnetic interactions are
frustrated due to the highly symmetric crystal lattice. As a result, we observed a
non-coplanar skyrmion vortex lattice (SkL) on very small dimensions (λ~2-3 nanometers).
We studied the resulting giant emergent magnetic ﬁeld in transport experiments.
Recently, we are also searching for new families of topological spin-vortices in frustrated
magnets.

2011 Dipl. Phys., Department of Physics, Technical Universityof Munich, Munich, Germany
2017 Ph.D., Department of Physics, Princeton University,
Princeton, NJ, USA
2017 Postdoctoral Researcher, RIKEN Center for Emergent
Matter Science (CEMS)
2018 Alexander von Humboldt / JSPS Research Fellow andVisiting Researcher at RIKEN CEMS
2019 Project Lecturer, Quantum-Phase Electronics Center,
School of Engineering, The University of Tokyo
2019 Unit Leader, Topological Quantum Matter Research Unit,
Cross-Divisional Materials Research Program, RIKEN
CEMS (-present)
2021 Associate Professor, Department of Applied Physics,
School of Engineering, The University of Tokyo (-present)
2021 Project Associate Professor, Quantum-Phase Electronics
Center, School of Engineering, The University of Tokyo(-present)

OutlineSkyrmions in hexagonal intermetallic Gd3Ru4Al12. (a) Pink spheres indicate Gd3+ moments on thebreathing Kagome sublattice. (b) Illustration of skyrmion spin structure. (c) Phase diagram with manymagnetic phases observed due to competing interactions. (d) Large topological Hall signal (greyshaded). (e) Real space image of skyrmions and (f) its Fourier transform.

Publications

Publications

1. L. Spitz, T. Nomoto, S. Kitou, H. Nakao, A. Kikkawa, S. Francoual, Y. Taguchi, R. Arita, Y. Tokura, T.-h.
Arima, and M. Hirschberger, “Entropy-assisted, long-period stacking of honeycomb layers in an AlB2-typesilicide”, J. Am. Chem. Soc., 144, 37, 16866–16871 (2022).
2. M. Hirschberger, L. Spitz, T. Nomoto, T. Kurumaji, S. Gao, J. Masell, T. Nakajima, A. Kikkawa, Y. Yamasaki,
H. Sagayama, H. Nakao, Y. Taguchi, R. Arita, T.-h. Arima, and Y. Tokura, “Topological Nernst Effect of the
Two-Dimensional Skyrmion Lattice”, Phys. Rev. Lett., 125, 076602 (2020).
3. M. Hirschberger, T. Nakajima, S. Gao, L. Peng, A. Kikkawa, T. Kurumaji, M. Kriener, Y. Yamasaki, H.
Sagayama, H. Nakao, K. Ohishi, Kakurai, Y. Taguchi, X. Yu, T.-h. Arima, and Y. Tokura “Skyrmion phaseand competing magnetic orders on a breathing kagome lattice”, Nat. Commun., 10, 5831 (2019).
4. M. Hirschberger, S. Kushwaha, Z. Wang, Q. Gibson, S. Liang, C.A. Belvin, B.A. Bernevig, R.J. Cava, and
N.P. Ong, “The chiral anomaly and thermopower of Weyl fermions in the half-Heusler GdPtBi”, Nat. Mater.,
15, 1161 (2016).
5. M. Hirschberger, R. Chisnell, Y.S. Lee, and N.P. Ong, “Thermal Hall effect of spin excitations in a kagomemagnet”, Phys. Rev. Lett., 115, 106603 (2015).

46

We study the interplay between magnetic order, inparticular non-coplanar spin arrangements such as
magnetic skyrmions, and the electronic band structure
in solids. Particular emphasis is put on compoundswith the potential to be grown in thin-ﬁlm form and on
realizing new types of protected surface states incorrelated materials. Methods include materials searchguided by density functional theory calculations, crystal synthesis using a variety of solid state techniques,
and ultra-high resolution transport measurements (upto very high magnetic ﬁelds). We collaborate closelywith other researchers at RIKEN and beyond toresolve the magnetic structure of new materials using
scattering and imaging experiments.

Topological Materials Design Research Unit
Motoaki Hirayama (Ph.D.), Unit Leader
motoaki.hirayama@riken.jp
Research ﬁeld
Physics, Materials Science

Keywords
First-principles calculations, Theoretical materials
design, Topological materials, Majorana fermions andparafermions, Spin-orbit interaction

Brief resume
2013 Ph.D., Department of Applied Physics, University of
TokyoElectrides as a new platform of
topological materials
Our unit propose e lectrides as a new platform of topological materials. Electrides are agroup of materials in which electron e- exists in the interstitial region and stabilizes the
structure as an anion. Electrides are being studied in the ﬁeld of catalysis because of theirsmall work function. For example, in the layered material Sc2C (Fig. (a)), electrons enter
the cavities between the layers and exhibit insulating properties as shown in Fig. (b). The
2+

2013 Postdoctoral Researcher, Nanosystem ResearchInstitute, AIST2015 Project Assistant Professor, Department of Physics,
Tokyo Institute of Technology
2017 Research Scientist, First-Principles Materials Science
Research Team, RIKEN Center for Emergent Matter
Science2020 Unit Leader, Topological Materials Design Research Unit,
Cross-Divisional Materials Research Program, RIKEN
Center for Emergent Matter Science (-present)
2020 Project Associate Professor, Quantum-Phase Electronics
Center, The University of Tokyo (-present)-

charge density of [Sc2C] 2e extends to interlayer positions that are signiﬁcantly displaced
from the Sc2C layer due to the anionic electrons 2e-, resulting in a non-trivial system witha quantized large polarization. Reﬂecting the bulk topology, a topologically-protected
metallic state appears on the Sc2C surface (Fig. (c)). The metallic surface state originatesfrom the interstitial electron, and therefore ﬂoats above the Sc 2C surface (Fig. (d)). This
electron cloud has a small work function, making it possible to use Sc2C as a topologicalsubstrate for high-density electron doping. For example, one electron per Mo site can be
doped for MoS 2 (Fig. (e)). We
have discovered a variety of
topological electrides including
relativistic systems, which willlead to the development of
topological properties acrossscientiﬁc ﬁelds.

OutlineIn our unit, we explore novel materials and their properties using ﬁrst-principles calculations, which are
numerical methods for realistic materials. In particular,
we focus on the topological properties of the electronic band structure and search for topological materials
with non-trivial properties. We investigate the properties and applications of these unique electronic states.
We also include superconducting states and propose
the emergence of Majorana fermions. In addition, wedevelop ab initio methods to treat correlation effects
and design a wide range of materials including strongly correlated systems and magnetic systems. We
design materials across a wide range of ﬁelds, including materials in the chemical and materials ﬁelds, suchas electrides.

(a) Crystal structure of the topological electride [Sc2C]2+2e-, (b) band structure of Sc2C, (c) band
structure of the Sc2C (111) surface, (d) ﬂoating topological surface state, (e) topological carrier doped
toPublications
MoS2

Publications
1. T. Yu, R. Arita, and M. Hirayama, “Interstitial-Electron-Induced Topological Molecular Crystals”, Adv. Phys.
Res., 2200041 (2023).
2. Y. Ohtsuka, N. Kanazawa, M. Hirayama, A. Matsui, T. Nomoto, R. Arita, T. Nakajima, T. Hanashima, V.
Ukleev, H. Aoki, M. Mogi, K. Fujiwara, A. Tsukazaki, M. Ichikawa, M. Kawasaki, Y. Tokura, “Emergence ofspin-orbit coupled ferromagnetic surface state derived from Zak phase in a nonmagnetic insulator FeSi”,
Sci. Adv., 7, eabj0498 (2021).
3. M. Hirayama, T. Tadano, Y. Nomura, and R. Arita “Materials design of dynamically stable d 9 layered
nickelates”, Phys. Rev. B, 101, 075107 (2020).
4. M. Hirayama, S. Matsuishi, H. Hosono, and S. Murakami, “Electrides as a New Platform of Topological
Materials”, Phys. Rev. X, 8, 031067 (2018).
5. M. Hirayama, R. Okugawa, T. Miyake, and S. Murakami, “Topological Dirac nodal lines and surface chargesin fcc alkaline earth metals”. Nat. Commun., 8, 14022 (2017).

47

Index3D magnetic imaging

Electronic States Microscopy R.T. (X.Z. Yu)

18

A

Excited state

Emergent Supramolecular Materials R.T. (Y.-J. Pu) 28

Explainable AI

Quantum Condensate R.T. (M. Ueda)

32

F
Analytical electron microscopy Electronic States Microscopy R.T. (X.Z. Yu)

18

Anomalous photovoltaic effect Emergent Device R.T. (Y. Iwasa)

24

First-principles calculations First-Principles Materials Science R.T. (R. Arita)

15

Computational Materials Function R.U. (Y. Xu)

41

BTopological Materials Design R.U. (M. Hirayama) 47
Berry phase physics

Strong Correlation Physics R.G. (Y. Tokura)

6

Flux quantum

Emergent Phenomena
Observation Technology R.T. (D. Shindo)33

Frustrated quantum magnets Quantum Matter Theory R.T. (A. Furusaki)

13

Topological Quantum Phenomenon R.U. (T. Liang) 43
Topological Quantum Matter R.U. (M. Hirschberger) 46
Biomimetics

Emergent Soft Matter Function R.G. (T. Aida)

21

Emergent Bioinspired Soft Matter R.T. (Y. Ishida) 23
Bose-Einstein condensation Quantum Condensate R.T. (M. Ueda)

Topological Quantum Matter R.U. (M. Hirschberger) 46
H32
High-resolution electron microscopy

CElectronic States Microscopy R.T. (X.Z. Yu)

Carbon nanotube

Quantum Effect Device R.T. (K. Ishibashi)

37

Chemical analysis

Materials Characterization S.T. (D. Hashizume)

30

Cold atoms

Quantum Condensate R.T. (M. Ueda)

32

Colloidal Quantum Dot

Emergent Supramolecular Materials R.T. (Y.-J. Pu) 28

18

High-temperature superconductor
Strong Correlation Quantum Transport R.T. (Y. Tokura) 11
Low-Dimensional Transport R.U. (D. Zhang)

42

I

Computational condensed matter physics
Computational Quantum Matter R.T. (S. Yunoki) 14
Condensed matter physics Low-Dimensional Transport R.U. (D. Zhang)

Imaging

Emergent Phenomena
Observation Technology R.T. (D. Shindo)

42

Topological Quantum Phenomenon R.U. (T. Liang) 43

Strong Correlation Quantum Structure R.G. (T. Arima) 9

Strong Correlation Quantum Transport R.T. (Y. Tokura) 11

Interface electrons

Strong Correlation Theory R.G. (N. Nagaosa)

DInterstate transition

Emergent Supramolecular Materials R.T. (Y.-J. Pu) 28

Differential phase-contrast microscopy

J

Crystal engineering

Emergent Molecular Assembly R.U. (H. Sato)

40

Electronic States Microscopy R.T. (X.Z. Yu)

18

Domain wall

Spin Physics Theory R.T. (G. Tatara)

36

Dynamic control

Emergent Supramolecular Materials R.T. (Y.-J. Pu) 28

Edelstein effect

Quantum Nano-Scale Magnetism R.T. (Y. Otani) 34

Education of users

Semiconductor Science R. S. T. (F. Matsukura)Electric-ﬁeld device

Emergent Functional Interface R.U. (M. Nakano) 45

Electron correlation

Quantum Matter Theory R.T. (A. Furusaki)

Electron diffraction

Strong Correlation Quantum Structure R.G. (T. Arima) 9

Electron holography

Emergent Phenomena
Observation Technology R.T. (D. Shindo)33

Electron microscopy

Materials Characterization S.T. (D. Hashizume)

30

Emergent Phenomena
Observation Technology R.T. (D. Shindo)

33

Low-Dimensional Transport R.U. (D. Zhang)

42

L

13

Emergent Soft Matter Function R.G. (T. Aida)

21

Electronic states

Electronic States Microscopy R.T. (X.Z. Yu)

18

Emergent electromagnetism Strong Correlation Theory R.G. (N. Nagaosa)

7

Topological Quantum Matter R.U. (M. Hirschberger) 46
Emergent Soft Matter Function R.G. (T. Aida)
Emergent Bioengineering Materials R.T. (Y. Ito)

Emergent Bioinspired Soft Matter R.T. (Y. Ishida) 23

29

Electronic States Microscopy R.T. (X.Z. Yu)

18

Emergent Phenomena
Observation Technology R.T. (D. Shindo)

33

Low-Dimensional Transport R.U. (D. Zhang)

42

M
Magnetism

Computational Quantum Matter R.T. (S. Yunoki) 14
Strongly Correlated Spin R.T. (H. Furukawa)

17

Topological Quantum Matter R.U. (M. Hirschberger) 46
Magnetoelectric effectStrong Correlation Theory R.G. (N. Nagaosa)

Magnon-phonon coupling

Quantum Nano-Scale Magnetism R.T. (Y. Otani) 34

7

Majorana fermions and parafermions
Quantum System Theory R.T. (D. Loss)

35

Topological Materials Design R.U. (M. Hirayama) 47

27

21

Physicochemical Soft Matter R.T. (F. Araoka)

Low dimensional superconductors

21

Environmentally friendly material
Emergent Soft Matter Function R.G. (T. Aida)

Lorentz microscopy

39

Electronic material

Energy conversion

Josephson effect7

Liquid crystals, polymeric materials

E

Metamaterial

Spin Physics Theory R.T. (G. Tatara)

36

Molecular design

Emergent Soft Matter Function R.G. (T. Aida)

21

Molecular evolutionary engineering
Emergent Bioengineering Materials R.T. (Y. Ito)

48

33

Interface electronic structure27

Monopole

Spin Physics Theory R.T. (G. Tatara)

36

Multiferroics

Strong Correlation Physics R.G. (Y. Tokura)

6

Strong Correlation Materials R.G. (Y. Taguchi)

10Emergent Spectroscopy R.U. (Y. Takahashi)

44

Precise polymer synthesis

Emergent Bioengineering Materials R.T. (Y. Ito)

27

Nanodevices

Quantum System Theory R.T. (D. Loss)

35

Quantum Electron Device R.T. (M. Yamamoto)

38

Emergent Phenomena
Observation Technology R.T. (D. Shindo)

33

Nanomagnetism

Quantum Nano-Scale Magnetism R.T. (Y. Otani) 34
Nanometer scale fabrication Semiconductor Science R. S. T. (F. Matsukura)

39

Nanostructure control

Emergent Functional Polymers R.T. (K. Tajima)

26

Nanotubes

Emergent Device R.T. (Y. Iwasa)

24

Neutron scattering

Strong Correlation Quantum Structure R.G. (T. Arima) 9

Non-reciprocal effectNonreciprocal transport

Strongly Correlated Spin R.T. (H. Furukawa)

17

Strong Correlation Theory R.G. (N. Nagaosa)

7

Emergent Spectroscopy R.U. (Y. Takahashi)

44

Emergent Device R.T. (Y. Iwasa)

24

Quantum coherence

Quantum Functional System R.G. (S. Tarucha)

31

Quantum Electron Device R.T. (M. Yamamoto)

38

Quantum correlations

Quantum Electron Device R.T. (M. Yamamoto)

38

Quantum dots

Emergent Device R.T. (Y. Iwasa)

24

Quantum Effect Device R.T. (K. Ishibashi)

37

Quantum entanglement

Quantum Functional System R.G. (S. Tarucha)

31

Quantum information devices Quantum Functional System R.G. (S. Tarucha)

31

Quantum Effect Device R.T. (K. Ishibashi)

37

Quantum materials

Emergent Photodynamics R.T. (N. Ogawa)19

Quantum simulation

Quantum Condensate R.T. (M. Ueda)

32

Quantum thermodynamics Quantum Condensate R.T. (M. Ueda)

32

S
Sample characterization

Semiconductor Science R. S. T. (F. Matsukura)

39

Scanning probe microscopy

Dynamic Emergent Phenomena R.T. (F. Kagawa) 20

Scanning tunneling microscopy
Emergent Phenomena Measurement R.T. (T. Hanaguri) 12
Self-assembly

O

27

Q

N
Nanobiotechnology

Emergent Bioengineering Materials R.T. (Y. Ito)

Emergent Soft Matter Function R.G. (T. Aida)

21

Emergent Bioinspired Soft Matter R.T. (Y. Ishida) 23
Optical properties

Physicochemical Soft Matter R.T. (F. Araoka)

29

Opto-spintronics

Emergent Photodynamics R.T. (N. Ogawa)

19

Organic electronics

Emergent Soft System R.T. (T. Someya)

25

Emergent Functional Polymers R.T. (K. Tajima)

26

Physicochemical Soft Matter R.T. (F. Araoka)

29

Organic ferroelectrics

Organic ﬁeld-effect transistor Emergent Molecular Function R.T. (K. Takimiya)
Emergent Soft System R.T. (T. Someya)

22
25

Organic light emitting devices
25

Organic nonlinear optics

Physicochemical Soft Matter R.T. (F. Araoka)

29

Organic semiconductor

Emergent Molecular Function R.T. (K. Takimiya)

22

Emergent Supramolecular Materials R.T. (Y.-J. Pu) 28
Organic sensors

Emergent Soft System R.T. (T. Someya)

25

Organic solar cells

Emergent Molecular Function R.T. (K. Takimiya)

22

Emergent Soft System R.T. (T. Someya)

25

Emergent Functional Polymers R.T. (K. Tajima)

26

Emergent Molecular Function R.T. (K. Takimiya)

22

Organic thermoelectric materials
Emergent Molecular Function R.T. (K. Takimiya)

40

Emergent Supramolecular Materials R.T. (Y.-J. Pu) 28
Quantum Effect Device R.T. (K. Ishibashi)

37

Sensors

Emergent Bioengineering Materials R.T. (Y. Ito)27

Shift current

Strong Correlation Theory R.G. (N. Nagaosa)

7

Single electron manipulation

Quantum Electron Device R.T. (M. Yamamoto)

38

Strong Correlation Physics R.G. (Y. Tokura)

6

Strong Correlation Materials R.G. (Y. Taguchi)

10Strongly Correlated Spin R.T. (H. Furukawa)

17

Topological Quantum Matter R.U. (M. Hirschberger) 46
Soft material

Emergent Soft Matter Function R.G. (T. Aida)

21

Emergent Bioinspired Soft Matter R.T. (Y. Ishida) 23
Soft-matter physics

Physicochemical Soft Matter R.T. (F. Araoka)

Spectroscopy

Dynamic Emergent Phenomena R.T. (F. Kagawa) 20

Spin current

Spin Hall effect22

29

Quantum Nano-Scale Magnetism R.T. (Y. Otani) 34
Spin Physics Theory R.T. (G. Tatara)

36

Strong Correlation Theory R.G. (N. Nagaosa)7

Quantum Nano-Scale Magnetism R.T. (Y. Otani) 34
Spin-orbit interaction

P

26

Emergent Molecular Assembly R.U. (H. Sato)

Semiconductor nanowire

Skyrmion

Emergent Soft System R.T. (T. Someya)

Organic Synthesis

Semiconductor nanoparticle

Emergent Functional Polymers R.T. (K. Tajima)

Strong Correlation Physics R.G. (Y. Tokura)

6

Strong Correlation Quantum Transport R.T. (Y. Tokura) 11
Phase control

Dynamic Emergent Phenomena R.T. (F. Kagawa) 20

Photocurrent spectroscopy Emergent Photodynamics R.T. (N. Ogawa)

19

Photoelectric conversion material
Emergent Soft Matter Function R.G. (T. Aida)

Quantum System Theory R.T. (D. Loss)

35

Spin Physics Theory R.T. (G. Tatara)

36

Topological Quantum Matter R.U. (M. Hirschberger) 46
21

Photoelectron spectroscopy

Electronic States Spectroscopy R.T. (K. Ishizaka) 16

Pi-electronic compound

Emergent Molecular Function R.T. (K. Takimiya)

22

Polymer synthesis

Emergent Functional Polymers R.T. (K. Tajima)

26

Porous materials

Emergent Molecular Assembly R.U. (H. Sato)40

Topological Materials Design R.U. (M. Hirayama) 47
Spintronics

Quantum Nano-Scale Magnetism R.T. (Y. Otani) 34
Spin Physics Theory R.T. (G. Tatara)

Stimuli-responsive material Emergent Soft Matter Function R.G. (T. Aida)

36
21

Emergent Bioinspired Soft Matter R.T. (Y. Ishida) 23

49

IndexStrongly correlated electron system

Two-dimensional electron system

Strong Correlation Physics R.G. (Y. Tokura)

6

Strong Correlation Materials R.G. (Y. Taguchi)

10

Quantum Electron Device R.T. (M. Yamamoto)38

Two-dimensional materials (2D materials)

Strong Correlation Quantum Transport R.T. (Y. Tokura) 11

Emergent Device R.T. (Y. Iwasa)

Computational Quantum Matter R.T. (S. Yunoki) 14

Emergent Functional Interface R.U. (M. Nakano) 45

First-Principles Materials Science R.T. (R. Arita)

15

24

U

Electronic States Spectroscopy R.T. (K. Ishizaka) 16
Strongly Correlated Spin R.T. (H. Furukawa)

17

Ultrafast spectroscopy

Emergent Photodynamics R.T. (N. Ogawa)

19

Ultrafast time-resolved TEM

Dynamic Emergent Phenomena R.T. (F. Kagawa) 20
Quantum System Theory R.T. (D. Loss)

35

44

Topological Quantum Matter R.U. (M. Hirschberger) 46
Strongly-correlated oxide

Emergent Functional Interface R.U. (M. Nakano) 45

Structure science

Strong Correlation Quantum Structure R.G. (T. Arima) 9

Superconductivity

Strong Correlation Theory R.G. (N. Nagaosa)

7

Emergent Phenomena Measurement R.T. (T. Hanaguri) 12

Electronic States Spectroscopy R.T. (K. Ishizaka) 16

Emergent Photodynamics R.T. (N. Ogawa)
Unconventional Hall effect Strong Correlation Interface R.G. (M. Kawasaki)

Surface/Interface

Strongly Correlated Spin R.T. (H. Furukawa)

17

Emergent Device R.T. (Y. Iwasa)

24

Emergent Molecular Assembly R.U. (H. Sato)40

Terahertz spectroscopy

Emergent Spectroscopy R.U. (Y. Takahashi)

44

Theoretical materials design First-Principles Materials Science R.T. (R. Arita)

15

Computational Materials Function R.U. (Y. Xu)

41

Topological Materials Design R.U. (M. Hirayama) 47
Thermoelectric effectStrong Correlation Materials R.G. (Y. Taguchi)

10Emergent Device R.T. (Y. Iwasa)

24

Computational Materials Function R.U. (Y. Xu)

41

Topological Quantum Phenomenon R.U. (T. Liang) 43
Thin ﬁlms and interfaces

Strong Correlation Interface R.G. (M. Kawasaki)

8Computational Materials Function R.U. (Y. Xu)

41

Emergent Functional Interface R.U. (M. Nakano) 45
Topological electronics
Topological Insulators

Strong Correlation Interface R.G. (M. Kawasaki)

8Strong Correlation Physics R.G. (Y. Tokura)

6

Strong Correlation Quantum Transport R.T. (Y. Tokura) 11
Emergent Phenomena Measurement R.T. (T. Hanaguri) 12

Topological materials

Quantum Matter Theory R.T. (A. Furusaki)

13

Strong Correlation Interface R.G. (M. Kawasaki)

8

Electronic States Spectroscopy R.T. (K. Ishizaka) 16
Topological Quantum Matter R.U. (M. Hirschberger) 46
Topological Materials Design R.U. (M. Hirayama) 47
Topological particles

Quantum Functional System R.G. (S. Tarucha)

Topological quantum matters Quantum System Theory R.T. (D. Loss)
Computational Materials Function R.U. (Y. Xu)

31
35
41

Topological Quantum Phenomenon R.U. (T. Liang) 43

50

Topological superconductivity Quantum Matter Theory R.T. (A. Furusaki)

13

Quantum Effect Device R.T. (K. Ishibashi)

37

8Strong Correlation Interface R.G. (M. Kawasaki)

8

Low-Dimensional Transport R.U. (D. Zhang)

42

V
Van der Waals epitaxy

Emergent Functional Interface R.U. (M. Nakano) 45
X
X-ray crystal structure analysis
Materials Characterization S.T. (D. Hashizume)
X-ray scattering

T

19

Unconventional photovoltaic effectComputational Quantum Matter R.T. (S. Yunoki) 14
Electronic States Spectroscopy R.T. (K. Ishizaka) 16

44

Ultrafast/broadband spectroscopy

Topological Quantum Phenomenon R.U. (T. Liang) 43
Emergent Spectroscopy R.U. (Y. Takahashi)

Emergent Spectroscopy R.U. (Y. Takahashi)

30

Strong Correlation Quantum Structure R.G. (T. Arima) 9

Memo

51

52

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