RESEARCH HIGHLIGHTS 2013
A publication of the WPI Advanced Institute for Materials Research

RESEARCH HIGHLIGHTS 2013

WPI Advanced Institute for Materials Research
The Advanced Institute for Materials Research (AIMR) at Tohoku University in Sendai,
Japan, is one of nine World Premier International Research Center Initiative (WPI)
programs established with the support of the Japanese Ministry of Education, Culture,
Sports, Science and Technology (MEXT). Since its inauguration in 2007, the AIMR has
been bringing together world-class researchers from Japan and abroad to carry out cuttingedge research in materials science through interdisciplinary collaboration among its fourgroups — Bulk Metallic Glasses, Materials Physics, Soft Materials, Device/System — andMathematics Unit, with further integration supported by its Interface Unit.
Led by distinguished mathematician and director Motoko Kotani, the institute promotesinterdisciplinary research across the different groups while fostering young researchers
through the Global Intellectual Incubation and Integration Laboratory (GI3 Lab), whereinternational joint research is carried out in close cooperation with high-profile researchers
invited from countries throughout the world.
The AIMR is host to over 140 leading researchers, around half of whom come fromabroad, including 31 principal investigators. In addition to the research hub at Tohok­­u
University, the AIMR collaborates with research centers in China, France, Germany, Poland,
the United Kingdom and the United States. Close ties with other leading overseas institutes
are maintained through its Adjunct Professor and Associate Professor programs.

AIMResearch
AIMResearch is an online and print publication that highlights the scientific achievements
and activities of the AIMR. First published in June 2009, AIMResearch selects the mostimportant papers from the wealth of research produced by AIMR scientists throughout
the year, distilling the essence of the achievements into timely, concise and accessible
research highlights that are easy to digest, but retain all of the impact and importance of theoriginal research article. Published monthly on the AIMResearch website in both English
and Japanese, AIMResearch research highlights bring the very best of AIMR research to a
global audience of specialists and nonspecialists alike. AIMResearch also publishes a rangeof feature articles introducing other activities of the AIMR’s research groups. Visitors to thewebsite can register for monthly email alerts in either English or Japanese to keep abreast of
the latest developments and discoveries made at the AIMR.
research.wpi-aimr.tohoku.ac.jp

MESSAGE FROM THE DIRECTOR
2Making great progress through mathematics–
materials science collaboration
RESEARCH HIGHLIGHTSIN THE SPOTLIGHT

6

Graphene: Superconductivity thinned down

7

Supercapacitors: Better with a dash of gold

8

Organic spintronics: What matters in the long run

28

Materials and math makes green

9Superconductors: Riding the wave

30

Scaling the heights of materials

10

Microscopy: Where rubber meets the probe

11

Glasses: From disorder to disorder32

No bridge too far

12

Molecular electronics: In the right place

34

Reaping the rewards of

13

Fuel cells: Improved cathodic catalysts

14

Organic electronics: It’s all in the twist

15

Metallic glasses: All in order

16

Spintronics: Current generation

17

Batteries: A crash course in nanofabrication

18

Biomaterials: Getting cells in line

19

Raman spectroscopy: Pairing up for mercury detection

20

Graphene oxide: Responding to infrared light21

Spintronics: Using nature’s symmetries

22

Molecular magnets: Mathematical predictions

23

Batteries: The power of patterns

24Superhard materials: Shear resolution

research.wpi-aimr.tohoku.ac.jp
AIMResearch is a publication of the Advanced Institute for Materials Research(AIMR), a Tohoku University institute funded by the Ministry of Education,
Culture, Sports, Science and Technology of Japan.
© 2014 AIMR, Tohoku University. This publication may be reproduced in its
original form for personal use only. Modification or commercial use without priorpermission from the copyright holder is prohibited.

26

Comprehensive support for worldclass researchscience researcha mathematics–materials approach
36

Strengthening scientific exchange
and joint research

Editorial
AIMR, Tohoku University
2-1-1 Katahira, Aoba-ku, Sendai,
Miyagi 980-8577, Japan
Editor-in-Chief

Motoko Kotani

Managing Editor

Takashi Takahashi

Editorial Assistant

Tomoko Tagawa

ISSN 1884-491X

MESSAGE FROM THE DIRECTOR

Making great progress through mathematics–
materials science collaboration
As the director of the Advanced
Institute for Materials Research(AIMR), Tohoku University, it
is my great pleasure to welcome
you to the fifth print editionof AIMResearch: ResearchHighlights. Each month, wepublish a selection of the
AIMR’s distinguished research
results on our bilingual website,research.wpi-aimr.tohoku.ac.jp.
This publication is a collection of
the research highlights and featurearticles that appeared online
in 2013.
The AIMR was launched in 2007
as one of the inaugural research
centers under the World PremierInternational Research Center
Initiative (WPI) program initiated by the Japanese Ministry of
Education, Culture, Sports, Scienceand Technology (MEXT). The
program aims to create globally
visible research centers within
Japan. As such, the AIMR is fostering an ideal research environmentand becoming a hub that attracts
and circulates the world’s bestminds in materials science.
Another objective of the WPI
research centers is to create newscientific fields through interdisciplinary fusion. At the end of 2010,
the AIMR decided to establish
mathematics–materials sciencecollaboration at the institutional
level, creating a new materials
science that is appropriate for thetwenty-first century.
Society currently faces serious
environmental and energy
problems. To solve these problems
efficiently, we have to design andproduce functional materials
based on theoretical prediction.
As mathematics can provide acommon language for all scientificdisciplines — and has the power
to rearrange and integrate the fullbreadth of materials science —mathematics is our focus.
We spent the two years prior
to 2013 rearranging our internalorganization accordingly. We firstestablished the Mathematics Unit
consisting of two mathematics
laboratories. Then, members of
the AIMR reformulated materials
research themes from a mathematical viewpoint and set three
Target Projects: Non-equilibrium
Materials based on Mathematical
Dynamical Systems; Topological
Functional Materials; and Multiscale Hierarchical Materials basedon Discrete Geometric Analysis.
In setting these projects,
we identified the need forinterpreters who can bridge thegap between mathematics andmaterials science. Consequently,
we established the Interface Unit
that consists of young theoreticalresearchers in physics, chemistry
and applied mathematics. Rather
than belonging to a specificlaboratory, these independent
researchers can freely accessany materials scientists andmathematicians at the AIMR. Ourassembly of materials scientists
and mathematicians has now
completely fused and integrated.
We consulted widely on our
approach because the mathematics–materials collaboration isan ambitious challenge that isaccompanied by infinite possibilities of producing historicalbreakthroughs. The challenge isalso accompanied by the prospectof discovering problems attractive to both materials scientists
and mathematicians.
The AIMR achieved substantial
progress as a result of themathematics–materials sciencecollaboration during 2013.
For example, we successfully
characterized the atomic structureof icosahedral clusters in bulk
metallic glasses. We also revealed
atomic-scale competition in energy
and geometry for glass formation
using computational homology, anadvanced mathematical concept
but not a tool of conventional

theoretical physics. (This topic waspublished as a research highlight in2013 entitled “Metallic glasses: Allin order” and appears on page 16 of
this collection.)
Globalization also featured as anachievement in 2013. To strengthen
cooperation with international
satellites, AIMR Joint ResearchCenters (AJCs) establishedlaboratories at the University ofCambridge, United Kingdom, andthe University of California, Santa
Barbara (UCSB) in the UnitedStates. The AJCs have clear roles injoint research and in increasing the
AIMR’s international visibility.
In 2013, we held workshopswith UCSB in February andthe University of Cambridge inNovember. The AIMR’s international visibility will also benefit
from further reinforcement of our
Public Relations & Outreach Office.
In the seven years since its
inauguration, the AIMR has
produced promising results. Thisis largely due to a strong belief inthe significance of our approachand the fact that we are supported
by solid cooperation between
researchers and administrators. As
such, I believe that we can deliver
ground-breaking research findingsin the following years.
Motoko Kotani
Director
AIMR

Tohoku University’s Advanced Institute for Materials Research (AIMR)
promotes fusion research in materials science across disciplinary barriers

The AIMR is leading the world in facilitating collaboration between materials science and mathematics. In
an environment where more than half of the researchers come from abroad, scientists at the AIMR —young and international included — contribute to discussions and joint research projects, enabling the
AIMR to achieve world-leading research results.
AIMResearch’s website introduces cutting-edge research from the AIMR through research highlights,
spotlights, news and job vacancies. Access AIMResearch online now!

research.wpi-aimr.tohoku.ac.jp
Latest research highlights• Superhard materials: Shear resolution• Molecular magnets: Mathematical predictions• Batteries: The power of patterns• Graphene oxide: Responding to infrared light• Spintronics: Using nature’s symmetries

RESEARCH HIGHLIGHTS
The AIMR advances research in bulk metallic glasses, materials physics,
soft materials and device/system construction, and actively promotes
collaboration among these divisions toward the development ofground-breaking technologies that cross the boundaries of conventional
fields of study — bridging the disciplines of materials science, physics,
chemistry and precision, mechanical, electronics and informationengineering. The Mathematics Unit complements the AIMR’s research
activities, and the Interface Unit further supports their integration.

RESEARCH HIGHLIGHTS

Graphene

Superconductivity thinned down
Production of the thinnest possible carbon-based superconductor could herald
functionalized graphene materials

6

Ca

C

Reproduced from Ref. 1 © 2012 K. Kanetani et al.

Graphene has a well-earned reputation as a ‘wonder material’. Isolation ofthese one-atom-thick sheets of carbon
that make up graphite — a material
best known for its use in pencils — has
opened an avenue for the study and utilization of two-dimensional materials.
Bulk graphite has also attracted interest
in its own right, especially for its potential practical applications. In particular,
the insertion of substances between
its graphene layers to form ‘graphite
intercalation compounds’ (GICs) has
been investigated as a method for the
storage of lithium atoms within batteries. Interestingly, some GICs canalso conduct electricity without any
resistance — an attractive phenomenon
known as superconductivity.
Now, by trapping calcium atoms
between just two layers of graphene,
Katsuaki Sugawara and co-workers
from the AIMR and the Departmentof Physics at Tohoku University haveconstructed a carbon-based superconductor at its two-dimensional limit1 (seeimage). Their ‘sandwich’ material offers
the advantages of bulk graphite while
being as thin as it can possibly be. With
the production of this graphene–calcium material, the researchers have constructed the thinnest possible form of
the calcium-based GIC C6Ca.
Among the known superconducting
GICs, C6Ca is arguably the most interesting as it develops superconductivity
at a higher temperature than any other.
Sugawara and co-workers were able
to reduce the thickness of the graphite
layer that surrounds the calcium atoms
to the absolute minimum. The thin graphene–calcium–graphene material was
produced by first introducing lithium

SiC substrate
Schematic view of the calcium-based graphite intercalation compound (GIC) C6Ca. Calcium atoms (Ca, inyellow) are inserted between two sheets of graphene, which are made of carbon atoms (C, in gray). The
graphene–calcium sandwich is supported by a silicon carbide (SiC) substrate.

into a bilayer graphene film supported
by a silicon carbide (SiC) substrate — aless challenging task than the direct introduction of calcium, due to the smaller
size of the lithium atoms. Subsequently,
they replaced the intercalated lithium
atoms by depositing calcium onto thegraphene–lithium–graphene intermediate, followed by heating. “We had initially developed this method for making
millimeter-thick C6Ca, and have now
improved it for use in bilayer-graphenefilms,” explains Sugawara.
Despite the thinness of the material
they created, the scientists were able tosuccessfully perform a number of experiments on it. “The most importantresult of our study is the characterization of the electronic structure in thisthinnest limit of a GIC,” notes Sugawara.
“Our findings should form a basis forunderstanding superconductivity in
GIC systems.” The team now hopesthat the same approach will be usefulfor other GIC applications, including
the creation of efficient microbatteries.
“This research area should help to gain
a fundamental understanding of thephysics and chemistry relevant to stateof-the-art batteries using graphite as anelectrode,” says Sugawara.
1. Kanetani, K., Sugawara, K., Sato, T., Shimizu, R.,
Iwaya, K., Hitosugi, T. & Takahashi, T. Ca intercalated bilayer graphene as a thinnest limitof superconducting C6Ca. Proceedings of
the National Academy of Sciences USA
109, 19610–19613 (2012).

AIMResearch 2013

RESEARCH HIGHLIGHTS

Supercapacitors

Better with a dash of gold

Supercapacitors aim to surpass batteries
by combining immense energy storage
with lightening-quick charge times.
Manganese oxide (MnO2) is a promising material for these devices becauseof its low cost, nontoxic properties andultrahigh capacitance. However, thecompound’s intrinsically low conductivity renders electron transport difficult.
So far, only nanometer-thin films or
low-density nanoparticle dispersionsof MnO2 have displayed the desirable
supercapacitance, but unfortunately
these structures are too small to deliveradequate power for most applications.
Mingwei Chen, Jianli Kang andcolleagues from the AIMR at Tohoku
University have now devised a strategy
to boost the conductivity of MnO2 thickfilms by fashioning them into unconventional nanoporous electrodes thatincorporate gold atoms within their oxide
lattice1. First, the team synthesized a porous MnO2 electrode by electrochemicallydepositing a nanoscale film with needlelike arrangements onto a gold–polymer
substrate. Despite the structure providing
plenty of surface sites for energy storage, the electrode’s capacitance dropped
dramatically when the film’s thickness exceeded 350 nanometers, owing to MnO2’s
poor conductivity.
The researchers then bombarded the
MnO2 electrode with gold atoms from aphysical vapor deposition system, using
a process known as sputtering. Repeating
the sequence of MnO2 electrochemical growth followed by gold ‘doping’
several times enabled the constructionof micrometer-thick electrodes ready for
use as supercapacitors. X-ray and electron
microscopy analysis revealed that thistechnique replaces 10% of the MnO2 with

AIMResearch 2013

© 2013 Mingwei Chen

An innovative deposition technique may help to jumpstart a new generation ofhigh-speed energy storage materials

View of the crystal structure of manganese oxide (MnO2) (blue and red spheres) doped with an atom of gold(yellow sphere). New findings reveal that this kind of material is ideal for supercapacitors.

electron-rich gold dopant atoms that are
distributed evenly throughout the oxide(see image). Alternate layering of MnO2
and gold atoms ensures the dopants are
well-integrated within the oxide’s latticeand not just physically absorbed, Chen
notes. “The electrochemical deposition helps sputtered gold travel to theelectrode/electrolyte interface to occupy
MnO2 lattice sites.”
The gold-doped MnO2 was found tohave a capacitance 65% higher than thatof comparable pure films — the best
charge storage ever achieved from thick
MnO2 electrodes. The new material
showed outstanding stability and evenincreased its charge capacity after a few
hours’ use due to electrochemical dopant redistribution during voltammetric
cycling. Collaboration with Kazuto
Akagi’s research team at the AIMR

uncovered a fundamental theoreticalprinciple behind these findings: gold
dopants transfer electrons to manganeseand oxygen atoms equally, boosting theentire material’s conductivity.
“Manganese oxide is the most promising material for electrochemical supercapacitors,” says Chen, adding that “dopingis the easiest and best way to improveits conductivity.” By implementing anoften-considered but rarely realized
concept, the team is confident that their
doping approach will benefit futurecommercialization efforts of MnO2
thick-film devices.
1. Kang, J., Hirata, A., Kang, L., Zhang, X., Hou, Y.,
Chen, L., Li, C., Fujita, T., Akagi, K. & Chen, M.
Enhanced supercapacitor performance of
MnO2 by atomic doping. Angewandte ChemieInternational Edition 52, 1664–1667 (2013).

7

RESEARCH HIGHLIGHTS

Organic spintronics

What matters in the long run

An ability to control the spin of theelectron would enable the design ofspintronic devices that are more efficient than current electronic ones.
Research efforts have so far focusedon solid-state inorganic materials thatcan be fabricated to a high purity,
easily incorporated into devices andwhose composition can be precisely
controlled. However, organic materials
also pose several advantages, including
low processing costs and the opportunity to control their physical properties
through careful chemical modification.
Since organic compounds are
typically made from light elements— primarily carbon — the spin–orbit
interaction, which couples the spin
momentum with the angular momentum of the electron, is quite small. Thismeans that the electron spin can bepreserved for a long time and electronscan, in principle, travel long distances
without flipping their spin. Until recently, the longest distances travelled atroom temperature were in the few tensof nanometers and a greater distance
had only been observed at a low temperature. Xianmin Zhang and co-workers have now realized devices basedon an organic material in which theelectrons can travel distances of up to
110 nanometers at room temperature,
while preserving their spin1 (see image).
The researchers constructed theirdevices from films of fullerene (C60), a
molecule which has low spin–orbit interactions as it consists solely of carbon
atoms. The absence of hydrogen — common in other organic materials — serves
to reduce the hyperfine interactions
between electron and nuclear spins that
can induce spin-flipping events. Zhang

8© 2013 Miyazaki–Mizukami group

Experiments on fullerene films show that electron spins can be preserved for long
distances in optimized organic compounds

Illustration of the fullerene films in which electrons preserve their spins over long distances. Fullerenes (blue),electrons (green spheres) and electron spins (arrows) are shown.

and colleagues fabricated organic spin
valves, in which two ferromagnetic
electrodes are placed in contact withan organic layer, and measured theirmagnetoresistance, which is the difference in electrical resistance when thespin valve’s electrodes are magnetizedin the same or opposite direction.
Magnetoresistance is therefore ameasure of the conservation of theelectron’s spin polarization.
By studying devices composed fromvarious thicknesses of the C60 film, theteam observed a record value — of up
to 110 nanometers in length — for magnetoresistance at room temperature.
Zhang explains that it may be possible
to further improve on these results as,

according to theory, a spin length ofover 400 nanometers can be obtained in
crystalline C60 — although fabricating
films of such a well-ordered material
would be quite challenging.
According to Zhang, the significanceof the team’s results is not limited to
C60: an understanding of spin transport
in these films could inspire chemists
and engineers to design even more efficient compounds and devices.
1. Zhang, X., Mizukami, S., Kubota, T., Ma, Q.,
Oogane, M., Naganuma, H., Ando, Y. &Miyazaki, T. Observation of a large spin-dependent transport length in organic spin valves atroom temperature. Nature Communications
4, 1392 (2013).

AIMResearch 2013

RESEARCH HIGHLIGHTS

Superconductors

Riding the wave
The coexistence of superconductivity and a wave-like, charge-ordered phase in irondoped 1T-TaS2 offers a deeper understanding of high-temperature superconductivity

AIMResearch 2013Ta

© 2013 Ran Ang

Understanding the origin of superconductivityinhigh-temperature
superconductors remains a major
question in physics and is crucial forthe development of superconductorsthat can operate at higher temperatures.
However, unraveling the phenomenon iscomplicated by the fact that electronic
properties — such as magnetism —which usually prevent superconductivity, appear to play an important rolein the superconducting state at suchtemperatures. An international teamled by Takashi Takahashi and colleagues
from the AIMR at Tohoku University has
now shown that superconductivity may
coexist with these competing states1.
Superconductivity originates from theexistence of pairs of electrons that canroam a crystal without losing energy.
In conventional superconductors theformation of such electron pairs is facilitated by oscillations of the atoms in the
crystal. However, in high-temperature
superconductors other factors including
magnetism seem to play a role, despite
conventional theory determining thatmagnetism and superconductivity cannot coexist.
The researchers studied 1T-TaS2, a material consisting of layers of the elements
tantalum (Ta) and sulfur (S), as well as
its iron-doped derivatives. At lower temperatures the tantalum atoms in 1T-TaS2
arrange into a so-called ‘Star of David’
pattern (see image) and exhibit an insulating behavior in which periodic variations in the density of electrons — known
as charge-density waves (CDWs) — arise
across the material. Typically, superconductivity and the CDW state areconsidered to be mutually exclusive. Yet
the researchers found that when some of

Tantalum (Ta) atoms organize into a ‘Star of David’ pattern in the charge-density wave (CDW) phase of 1T-TaS2.

the tantalum atoms were replaced withiron, superconductivity could occur.
Takahashi and colleagues used highresolution angle-resolved photoemission
spectroscopy (ARPES) — a techniquein which light pushes electrons out ofa material — to investigate 1T-TaS2.
Measuring the energy and momentumof the ejected electrons provides a direct
window into a material’s electronic state.
The researchers identified a shallow electron pocket, believed to be characteristicof superconductivity, within 1T-TaS2
in the nearly commensurate CDW(NCCDW) state — a CDW phase that
forms at higher temperatures and particular concentrations of iron. “The uniquefeature of this method is to reveal theelectronic states responsible for the CDW
state as well as the superconducting state.

This would not be possible with otherexperimental approaches,” explains teammember Ran Ang.
The team was able to show that superconductivity and the CDW state are notseparated within 1T-TaS2 crystals but
instead coexist, representing an intrinsic
property and offering valuable insight
into the origin of high-temperature superconductivity. In addition, the ability
to control the CDW phase — by switching between the material’s normal metallic and insulating states — has potential
for application in electronic devices.
1. Ang, R., Tanaka, Y., Ieki, E., Nakayama, K., Sato, T.,
Li, L. J., Lu, W. J., Sun, Y. P. & Takahashi, T. Realspace coexistence of the melted Mott state andsuperconductivity in Fe-substituted 1T-TaS2.
Physical Review Letters 109, 176403 (2012).

9

RESEARCH HIGHLIGHTS

Microscopy

Where rubber meets the probe

Rubber is an important class of material with applications ranging fromhigh-performance devices to the humble
car tire. But characterizing the complex
blend of cross-linked polymers and carbon ‘filler’ particles that comprises rubber is far from straightforward. To better
investigate its composition, researchers
have turned to atomic force microscopy(AFM) — a technique that uses tiny,
oscillating silicon probes to measure thephysical properties of surfaces.
Conventional AFM instruments areunable to fully investigate the behaviorof rubber because their probes cannot
vibrate sufficiently fast across different
frequencies. Now, Ken Nakajima andcolleagues from the AIMR at Tohoku
University have solved this problem witha design that uses so-called ‘piezoelectric’
crystal actuators to boost the sensors’
vibrational capabilities1. While actuators
allow the three-dimensional scanningof surfaces, they are designed for large
movements, meaning that AFM instruments have a limited frequency range.
To obviate this issue, the researchers inserted an additional piezoelectric actuator — small, lightweight and with large
resonant frequencies — above the AFM
scanner to simultaneously oscillate thesample and probe it up to 20,000 times
per second.
The team tested its design on a seriesof isoprene and styrene–butadiene rubbers. First, they determined mechanicalcontact parameters by recording how
increasing force deformed the materials. They then compared the amplitude
and phase of AFM signals from therubbers to those of a solid mica surface.
Repeating the measurements at different frequencies generated ‘viscoelastic’

10

0.1μm
An atomic force microscopy ‘map’ of the mechanical loss of a rubber surface, which reveals an ‘island–sea’arrangement of immiscible rubbers. Such maps can be created at different frequencies to fully visualize thesurface’s nanoscale features.

parameters that described the rubbers’
dynamic deformation.
Two-dimensional ‘maps’ of the mechanical loss of a mixed rubber surface
were created using the AFM scanning
functions (see image). These revealed an‘island’-like arrangement of nanoscale
isoprene rubbery regions surrounded
by a ‘sea’ of styrene–butadiene rubbery
regions. Critically, the immiscible natureof the rubbers only became clear when
scanning at a certain range of frequencies.
Nakajima notes that the ability tomeasure frequency-dependent deformation can eliminate many of the timeconsuming tests currently needed tocharacterize rubber. “In viscoelastic
materials, frequency and temperatureare believed to be related. Therefore,
measurements with narrow frequency

ranges must be performed at multiple
temperatures. Our instrument can carryout these measurements with a muchwider frequency range at a fixed temperature,” he says.
Furthermore, explains Nakajima, theAFM measurements match many of thefrequencies encountered during macroscopic testing. Such direct comparisonsof large- and nano-scale phenomena arevital to comprehend multi-component
systems. “Our technique can visualize
the viscoelastic nature of each component in high resolution, giving valuable
feedback for future materials design.”
1. Igarashi, T., Fujinami, S., Nishi, T., Asao, N. &Nakajima, K. Nanorheological mapping of
rubbers by atomic force microscopy.
Macromolecules 46, 1916–1922 (2013).

AIMResearch 2013

Reproduced, with permission, from Ref. 1 © 2013 American Chemical Society

A ground-breaking microscope design reveals the nanoscale mechanical propertiesof rubber surfaces in unprecedented detailRESEARCH HIGHLIGHTS

Glasses

From disorder to disorder
A new type of phase transition in amorphous materials raises fundamental
questions about glasses and could lead to faster computer memory

AIMResearch 2013

Arsenic (As)Selenium (Se)Heator light© 2013 Jiri Orava

Phase-change materials are of great
importance in modern computing due
to their use in rewritable optical disks
and computer memory. They are particularly suitable for these applications
as they can be made to undergo a fast,
reversible transition induced by light orelectrical pulses. These transitions cause
their molecular structure to change froman ordered crystal to an amorphousstate resembling that of glass. Materials
in these two states have vastly different
physical properties, such as their ability
to reflect light or conduct electricity, andthis phenomenon can be used to encode
the ‘on’ and ‘off ’ states of digital bits.
An international team of researchers,
including Jiri Orava from the AIMR at
Tohoku University, has now discovered acompletely new type of phase transitionin which the material switches between
two different amorphous states1. The
amorphous-to-amorphoustransition
is fundamentally different to known
amorphous-to-crystalline transitions,and even to previously known
amorphous–amorphoustransitions,according to Orava.
The researchers studied As50Se50,
which is composed of equal amounts ofarsenic (As) and selenium (Se). When
freshly deposited as a thin film, thematerial is amorphous but if heated tohigh temperatures and slowly cooled
it becomes crystalline. However, theteam discovered that when only moderately heated, As50Se50 transitions to adifferent — and stable — amorphousstate. Similarly, when irradiated bylaser light, the newly grown material
forms another stable amorphous state.
These two states can be distinguished bymeasuring the bonding energy between

Heating, as well as illuminating, a thin film of As50Se50 causes a reversible transition from one amorphous state
to another.

the arsenic and selenium atoms, which
provides a unique fingerprint for theatomic configuration.
Transitions between different amorphous states are not unknown, but
previously had only been observed inmaterials subjected to pressure. Thechange studied here can be induced
through heating, suggesting that a further mechanism is responsible for theseamorphous-to-amorphous transitions.
This mechanism is of particular interest
because the material can be reversibly
switched between the two amorphousstates through successive annealing
and laser-exposure cycles. Switching isthought to occur at milli- to microsecond intervals.
Reversible
switching
betweenamorphous states resembles previously
discovered
amorphous-to-crystallinetransitions used in other applications.
However, the new system offers theadvantage that the switching process
requires far less energy. “The changes inatomic arrangement take place with arelatively low cost of energy; no melting
is required,” comments Orava. Moreover,the new switching paradigm involves far
fewer atoms than switching to an ordered
crystal, suggesting it could be used to create computer memory devices. Verifying
the dynamics of this transition and its
benefit for applications remains an aim of
future research, says Orava.
1. Kalyva, M., Orava, J., Siokou, A., Pavlista, M.,
Wagner, T. & Yannopoulos, S. N. Reversible
amorphous-to-amorphous transitions inchalcogenide films: Correlating changes instructure and optical properties. Advanced
Functional Materials 23, 2052–2059 (2012).

11

RESEARCH HIGHLIGHTS

Molecular electronics

In the right place

A fundamental discrepancy exists
between the basic building blocks
that underpin modern engineeringand those found in natural organisms:
while computers and electronic circuits
are based on inorganic materials,
such as silicon, biological processes
revolve around organic molecules.
Increasingly, researchers are striving
to combine the two to fabricate complex artificial devices from organic
molecules. Ikutaro Hamada, Masaru
Tsukada and co-workers from the
AIMR at Tohoku University and the
University of Tokyo have now shownhow the right choice of metal electrodes and operational conditions canenhance electronic performance1.
Molecular electronic devices are
particularly interesting for a number of
spintronic applications, which exploit
the electron’s magnetic property, known
as ‘spin’. “The realization of spintronic
devices consisting of single molecules
promises highly functional sensing,logic (computing) and informationstorage devices,” says Hamada, amember of the research team. Until
now, however, spin-based effects havenot been strong enough to use inpractical applications.
While the performance of a molecularelectronic device would be chiefly dictated by the organic molecule, contact
between the molecule and the adjacentmetallic electrodes also plays a key role.
The researchers fabricated devices featuring two magnetic nickel electrodes
separated by only 1 nanometer — farenough apart to accommodate thefullerene (C60) molecule (see image).
To create this precisely sized gap,
they used an electromigration-based

12

S

N

S

N

An illustration of the molecular electronic device’s geometry, with a fullerene (C60) molecule (red, center)embedded within magnetic nickel electrodes. N and S represent the north and south poles, respectively, of thedevice’s magnetic contacts.

process to move nickel atoms out of
the electrodes, slowly closing the space
between them.
The team then studied the effect of
the electrodes’ electronic levels on theproperties of the spintronic device
by measuring the change in electricalresistance when they applied different
external magnetic fields, a property
known as magnetoresistance. By varying the voltage applied, the researchers
could tune the device to observe achange in resistance of up to –80%.
Theoretical calculations revealed thathybridization at the nickel–C60 interface may be responsible for the observation of this unusual negative value
and, in addition, magnetoresistance
was maximal when the applied voltages led to the perfect alignment of theelectron spins in the C60 molecule andthe nickel electrodes.
These findings demonstrate thatmolecular electronic devices should beenvisaged as a whole since it is crucial
to realize an appropriate combination of
metallic contacts and organic molecules.
Hamada is confident that the team’s approach is applicable to a range of related
devices. “Using the theory developed in
the present work, I believe that it is possible to predict the properties of spintronic
devices made from other moleculesand electrodes.”1. Yoshida, K., Hamada, I., Sakata, I., Umeno, A.,
Tsukada, M. & Hirakawa, K. Gate-tunable large
negative tunnel magnetoresistance in Ni−C60−Nisingle molecule transistors. Nano Letters13, 481−485 (2013).

AIMResearch 2013

Reproduced, with permission, from Ref. 1 © 2013 American Chemical Society

Precise alignment of the electronic states in metal contacts and organic molecules isneeded to optimize performance in molecular electronic devices

RESEARCH HIGHLIGHTS

Fuel cells

Improved cathodic catalysts
An electrochemical dealloying method allows the preparation of highly active andtunable platinum–copper catalysts for the oxygen reduction reaction

AIMResearch 2013

O2

© 2013 Mingwei Chen

The development of cheap and efficientfuel cells — devices that convert chemical energy into electricity — is a key
component of the push toward cleaner
energy sources. Instead of burning fuelto produce heat, fuel cells extract energy
as electrons, which can then be fed into
an electrical circuit. In the most basic
example — the proton exchange membrane fuel cell (PEMFC) — hydrogen gas
is oxidized to protons and electrons at
one electrode. These electrons then passto the other electrode, via an electricalcircuit, where they reduce oxygen. Lastly,
the resulting oxide anions combine withthe protons, which have moved througha membrane, to form water — completing the same conversion as occurs whenhydrogen is burnt as a fuel.
Although commercially available
fuel cell systems use platinum absorbed
onto carbon to catalyze the oxygen
reduction reaction (ORR), the rate of
the reaction is still low, meaning thata large amount of expensive and scarce
platinum is required to achieve an efficient reaction. Now, Mingwei Chen and
Xingbo Ge from the AIMR at Tohoku
University and co-workers have createda cheap and active ORR platinum–copper catalyst1. Their system consists ofa nanoporous platinum–copper alloy
core covered by a thin skin of pureplatinum (see image).
Previous research revealed that the
precise ratio of platinum to copperin the core of these nanoparticulate
catalysts is particularly important for
their function. “Controlling the composition of bimetallic particles at thenanoscale is extremely difficult,” says
Chen. “Our electrochemical dealloying
can selectively dissolve the copper from

H2O

An illustration of the nanoporous platinum–copper catalyst developed for use in the oxygen reduction
reaction of fuel cells.

an alloy and is much easier to control.”The dealloying process itself is governedby the voltage that is applied, allowing
the final composition of the catalyst
to be tuned and, in turn, the optimum
catalyst to be identified.
Chen and his co-workers showedthat while the catalytic activity of theirmaterial can be attributed to the thinlayer of pure platinum at its surface, thisproperty can be honed by changing thecomposition of the catalyst’s alloy core.
This is due to the way in which the atoms
in the thin layer of platinum bind to thecore. Correspondingly, by adjusting theplatinum–copper ratio of the core, theteam was able to produce a nanoporous
material that outperforms commercial
platinum on carbon catalysts.
“We are now using our dealloying
method to prepare other bimetallic
catalysts for energy-related applications,” says Chen. “In addition, we areplanning industrial collaborations topromote the practical applications ofthese catalysts.”
1. Ge, X., Chen, L., Kang, J., Fujita T., Hirata, A.,
Zhang, W., Jiang, J. & Chen, M. A core-shell nanoporous Pt–Cu catalyst with tunable compositionand high catalytic activity. Advanced Functional
Materials 23, 4156-4162 (2013).

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RESEARCH HIGHLIGHTS

Organic electronics

It’s all in the twist

Organic light-emitting field-effect transistors (OLETs) are innovative devices
that combine brilliant light production
with fast electronic switching. With
the potential for application in flexible
low-cost displays and all-organic lasers,
OLET development has so far been hampered by a fundamental materials-based
challenge: the molecular interactions
that boost the mobility of charge carriers — a key transistor parameter —generally stifle light emission. In joint
experimental1 and theoretical2 studies,a multidisciplinary research team led
by Tienan Jin, Susumu Ikeda, Hiroyuki
Tamura and Katsumi Tanigaki from the
AIMR at Tohoku University has founda way to preserve electron mobility andgenerate higher luminescence efficiency
in OLETs using short chains of oxygenated aromatic molecules that form unusual bent structures in the crystal state.
Previously, the researchers synthesizeda promising organic semiconductor
known as BP2T by linking phenyl rings
and thiophene — a pentagonal aromatic
molecule containing a sulfur atom —into chains called oligomers. But despite
BP2T’s impressive bipolar amplification
characteristics, it only converted 38%
of incoming photons into luminescentemissions — a quantum yield too low for
OLET applications.
The team hypothesized that substituting thiophene’s sulfur atom withoxygen, which turns the molecule into
a furan ring, might enhance BP2T’s
performance. As oxygen atoms are
smaller than sulfur, this change shouldfavor the growth of more tightly
packed crystal structures — ideal formoving charge quickly. Furthermore,notes Jin, oligomerized furans have14

© 2013 Tienan Jin

A small molecular bending effect helps flexible light-emitting transistors tooutshine other optoelectronic technologies

A new aromatic compound that packs into ‘bent’ solid-state crystals can produce fast organic transistors that
emit bright luminescent light.

a strong track record of brightening
luminescent materials.
When the researchers synthesized
the new furan-containing compound,
BPFT, and incorporated it into an OLET
(see image), they saw their strategy pay
off — the luminescent quantum yield
jumped significantly to 51%. Next, theteam used X-ray crystallography to peer
into BPFT’s molecular structure. Insteadof being packed flatly like most aromatic
molecules, the furan oligomers had adistinct structural kink resulting in alternation between flat and bent alignmentsin the solid state.
Theoretical simulations revealed that
BPFT’s bending critically enhanced the
OLET’s photoluminescence. According
to Tamura, this particular packing
arrangement ‘breaks’ the equilibrium inherent to aromatic solids, causing
asymmetric electronic dipoles to form
during the transition to a photo-excitedstate. These dipoles then generate luminescent emissions that are forbidden in
totally symmetric complexes.
The researchers note that high-performance OLETs are rarely discovered

because diverse expertise is required tosynthesize, fabricate and model organic
semiconductor devices. Collaboration
between different research groups
proved crucial to identifying and tailoring the BPFT structure, they add.
“These results could not have beenaccomplished without long-term discussion and complete fusion within ourteam,” say Jin and Tamura.
1. Oniwa, K., Kanagasekaran, T., Jin, T., Akhtaruzzaman, Md., Yamamoto, Y., Tamura, H., Hamada, I.,
Shimotani, H., Asao, N., Ikeda, S. & Tanigaki, K.
Single crystal biphenyl end-capped furanincorporated oligomers: Influence of unusual
packing structure on carrier mobility andluminescence. Journal of Materials Chemistry C
1, 4163–4170 (2013).
2. Tamura, H., Hamada, I., Shang, H.,
Oniwa, K., Akhtaruzzaman, Md., Jin, T.,
Asao, N., Yamamoto, Y., Kanagasekaran, T.,
Shimotani, H. et al. Theoretical analysis on the
optoelectronic properties of single crystalsof thiophene-furan-phenylene co-oligomers:
efficient photoluminescence due to molecularbending. The Journal of Physical Chemistry C
117, 8072–8078 (2013).

AIMResearch 2013

RESEARCH HIGHLIGHTS

Metallic glasses

All in order

Most of the glasses that we encountereveryday are transparent and appear
to be rather ordinary. A closer look,however, reveals an intriguing composition: glasses are basically frozen liquids,
meaning that their atoms are randomly
arranged. Researchers from the AIMRat Tohoku University and international
collaborators have now shown that,surprisingly, the atoms of some glasses
containing metallic components also
display a local order that is based on
icosahedral geometric structures1. “Weprovide the first direct experimental
evidence of the existence of icosahedral
order in metallic glasses,” explains
Mingwei Chen, who led the researchteam to this discovery, which confirms
previous theoretical predictions.
Atoms in metals behave like perfectspheres, forming perfect crystals withatomic arrangements in the form offace-centered cubic (fcc) or bodycentered cubic (bcc) structures, forexample. Some metallic compounds
can also form glasses when cooled fastenough after melting. Scientists were
unsure as to why some metals form
glasses instead of crystallizing and assumed that upon fast cooling, atoms inthe metal are prevented from forming acrystal when they arrange into icosahedra. Such arrangements are similar inappearance to fcc crystal structures but
importantly cannot form large-scale,periodic structures (see image).
To study the structure of metallic
glasses, Chen, Akihiko Hirata andcolleagues used an angstrom-beamelectron diffraction technique in which
a tiny beam of electrons is guided ontoa sample of glass that is only a few atoms
wide. As the electrons pass through the

AIMResearch 2013

© 2013 Akihiko Hirata

The local atomic order of metallic glasses has been solved by electron-beamimaging at the atomic scale

The assumed icosahedral local atomic structure of metallic glasses (left, blue), the face-centered cubic (fcc)
structure of the corresponding metal crystal (right, red) and the actual distorted icosahedral arrangement ofmetallic glasses (center, yellow). The top and bottom rows show the same structures from a different angle.

glass, they are reflected by the atoms
and subsequently hit a screen thatrecords the pattern of their reflection.
With the help of computer analysis, thepositions of the atoms in the sample canbe determined from these patterns.
While the researchers were able
to confirm the icosahedral atomic
structure of metallic glasses, they also
found that the icosahedra were not perfectly formed, as previously assumed.
Interestingly, this slight distortion occurs in a way that makes the icosahedra
appear even closer in structure to the
fcc arrangement.
Beyond the discovery of local orderin metallic glasses, the angstrom-beamelectron diffraction technique itself is a

powerful way of studying compounds
on the atomic scale, comments Chen.
“We have just reached the starting
point to understand the true relationship between structure and propertiesof disordered materials. We now havea reliable experimental method to
directly investigate local atomic structure, and in the present case to show
the correlation between atomic-scale
structure and glass formation, andperhaps even the structural origin of
the glass transition.”
1. Hirata, A., Kang, L. J., Fujita, T., Klumov, B.,
Matsue, K., Kotani, M., Yavari, A. R. & Chen, M. W.
Geometric frustration of icosahedron in metallic
glasses. Science 341, 376–379 (2013).

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RESEARCH HIGHLIGHTS

Spintronics

Current generation
A detailed, quantitative analysis of spin current reveals the importance of effects
that are often overlooked in spintronic devices

16

External
magnetic fieldFerromagnetic(Ga,Mn)As
layer

Ohmic
contact

Reproduced from Ref. 1 © 2013 L. Chen et al.

The field of spintronics relies on exploiting the spin of the electron in thesame way that electronics is dependent
on the electron’s charge. Spintronics
holds exciting promise for the generation of ever smaller devices, andan important step in their realizationis the introduction of spin current tonon-magnetic materials.
In solids, the spin and momentumof an electron are coupled, leading
to a reciprocal conversion between
charge and spin currents that can be
described by a phenomenon known as
the spin Hall effect. Whereas the ‘direct
spin Hall effect’ converts current into
an accumulation of spins, the ‘inverse
spin Hall effect’ converts spin flow
into charge current. Interestingly, both
effects have been observed in metals
and semiconductors.
The inverse spin Hall effect is often
determined through the measurement of spin currents. Through aquantitative study, Lin Chen, Fumihiro
Matsukura and Hideo Ohno from the
AIMR at Tohoku University have now
unambiguously shown that other —galvanomagnetic — effects must be
taken into account when investigating
spin currents1.
Galvanomagnetic effects are observed when an external magnetic
field is applied to a current-carrying
conductor or semiconductor material.
To demonstrate their presence, Chen,
Matsukura and Ohno prepared asample comprising a ferromagnetic
layer, gallium manganese arsenide((Ga,Mn)As), on a semiconducting
substrate, gallium arsenide (p-GaAs).
The researchers generated a spin current in the (Ga,Mn)As and injected it

Semiconducting
p-GaAs layer

V
Illustration of the system devised to carry out the direct-current voltage measurements.

into the p-GaAs layer using a method
known as ‘spin pumping’. They thenmeasured the resulting direct-current
voltage in the p-GaAs layer. The study
was carried out under ferromagnetic
resonance (FMR) conditions, allowing
the magnetization of the ferromagnetic
layer to be characterized by FMR spectroscopy. In particular, the team examined the influences of the magnitude
and angle of the external magnetic field.
Analysis of the results revealed thatthe expected inverse spin Hall effect
was accompanied by a galvanomagnetic phenomenon — the ‘planar
Hall effect’ — in the ferromagnetic(Ga,Mn)As layer. “It is especially difficult to distinguish the inverse spin
Hall effect from the planar Hall effect,as they both produce lines of the same

symmetry and width in FMR spectra.
The difference lies in the angulardependence,” explain the researchers.
“These findings indicate the criticalimportance of separating the origins of
the direct-current voltage.”
The next step will be to show that thisstrategy is not just applicable to materials like (Ga,Mn)As that demonstratesignificant galvanomagnetic effects.
“This method should help further
our understanding of the physics ofspin current and the development of
new functional spintronic devices,”says Matsukura.
1. Chen, L., Matsukura, F. & Ohno, H. Direct-current
voltages in (Ga,Mn)As structures induced by ferromagnetic resonance. Nature Communications
4, 2055 (2013).

AIMResearch 2013

RESEARCH HIGHLIGHTS

Batteries

A crash course in nanofabrication

Developing high-capacity lithium ion
batteries is an important research problem
in materials science, and the realization ofhigh-quality thin films of lithium metaloxides is a step toward this goal. Pulsed
laser deposition (PLD) is a promising
method of creating such films. In this technique, atoms from a lithium-containing
source are vaporized using high-powered
bursts of light, and the resulting ‘plume’ ofplasma-phase atoms subsequently lands
on a designated surface as a nanometerthin coating.
However, when depositing films ofelectroactive materials such as lithium,the composition of the final thin film
often differs from that anticipated. This
‘non-stoichiometric’ behavior makes it
hard to predict the final result of particularfabrication strategies. Although the causesof the non-stoichiometry may be attributed to the volatile and chemically reactive nature of lithium atoms, quantitative
explanations of this phenomenon havebeen lacking. Daniel Packwood, Susumu
Shiraki and Taro Hitosugi from the AIMRat Tohoku University1 have made a discovery that should significantly improve thequality of PLD lithium-based thin films
thanks to a model that describes collisions
between high-energy atoms during thedeposition process.
During experimental trials, the researchers noticed that adding backgroundpressures of oxygen gas to the PLD
chamber could change the proportionof lithium in the thin film structures.
Intrigued by this result, they investigatedthis behavior — and the role of oxygen —with a theoretical model of the scattering
process as a series of two-dimensional,
head-on collisions between classical particles (see image).

AIMResearch 2013

Modified from Ref. 1 © 2013 American Physical Society

A collaborative study reveals that atomic collisions play critical roles during laserdriven assembly of electroactive thin films

A representation of the combined mathematical and materials study into the deposition of electroactive
thin films. The simulated trajectory of a lithium atom at an oxygen pressure of 10-6 torr (black line) is
superimposed over a plot of a lithium plasma plume after expanding for 5 microseconds at an oxygen pressureof 10-2 torr (background).

After synthesizing several prototypicallithium–manganese oxide thin films at
different oxygen pressures, Packwood,
Shiraki and Hitosugi compared the films’
chemical composition to the predictionsof their new model. The results were
striking: the theory correctly mirrored
the experimental results and revealed
that the presence of oxygen gas caused
lithium ions to scatter in erratic trajectories, often violently. Heavier manganese
atoms pushed through oxygen practically unimpeded. According to the team,these findings indicate that lighter atoms
will always show deficiencies when background gas pressures rise above a certain
threshold — thus, source materials must
be chosen carefully to achieve desired
lithium compositions.

Packwood notes that the model works
well because it captures the physics
behind the critical energy exchange occurring during atomic scattering. This
ensures reasonable thermal equilibriumin the model and predictions of spatial
distribution that have proven experimentally valid. The team expects that theiranalysis can guide the fabrication ofhigher-quality interfaces that would
lead to lithium ion batteries with higher
charge–discharge rates by reducing theeffects of electrical resistance.
1. Packwood, D. M., Shiraki, S. & Hitosugi, T.
Effects of atomic collisions on the stoichiometry of thin films prepared by pulsed
laser deposition. Physical Review Letters
111, 036101 (2013).

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RESEARCH HIGHLIGHTS

Biomaterials

Getting cells in line

Biomaterial supports that promote theorderly growth and differentiation ofcells are crucial for tissue engineeringand repair. However, reproducing thestructural and biological propertiesof the extracellular matrix, whichgoverns cell organization in the body,remains a challenge for materials
scientists. Now, Toshinori Fujie andAli Khademhosseini from the AIMRat Tohoku University and co-workers
from Japan, South Korea and the UnitedStates have devised a free-standing
ultrathin polymer film that mimics theinherent ability of this matrix to direct
cells. The resulting ‘nanomembrane’
exhibits nano- and microscale features,
similar to those of natural tissue1.
Numerous synthetic extracellular matrices have previously been developed,
including hydrogels and elastomers.
Unfortunately, unlike their naturalcounterparts, the size and componentsof such materials hinder the hierarchical assembly of cells into complex
tissue structures.
Using microfabrication techniques,
the researchers manufactured their film
from nanometer-sized polymer fibers
containing cell-adhesive domains, whichallowed them to replicate the basement membrane of tissues — a dense,
sheet-like structure that serves as acellular scaffold.
First, they prepared an ultrathin polystyrene film on a glass surface pre-coatedwith a sacrificial polymer layer. Next,
using a microscopic stamp, the researchers patterned the surface of the film withfeatures made from a fibronectin–carbon
nanotube composite to functionalize it
for cell alignment and adhesion. After
cell culture, they then dissolved the18

Reproduced, with permission, from Ref. 1 © 2013 American Chemical Society

A flexible artificial extracellular matrix is paving the way for new approaches toregenerative medicine

Differentiated muscle cells (green and blue) assembled on the ultrathin polymer film nanomembrane. The
free-standing micropatterned nanomembrane is shown inset.

initial polymer layer to release the cellpatterned nanomembrane.
In vitro cell studies showed that the
micropatterning facilitated the alignment of muscle progenitor cells, known
as myoblasts, on the nanomembrane.
The fibrous nanotubes also enhanced theelongation and differentiation of thesecells into functional myofibers. “These
results suggest that the film’s surface isa useful platform for studying cell−substrate interactions,” says Fujie.
The researchers were able to produce
films of various thicknesses — ranging
from tens to hundreds of nanometers —by tuning the polystyrene concentration.
Analyses of the thickness dependenceof the mechanical properties revealed
that, in addition to the free-standing
films being highly flexible, the thinner
films displayed greater flexibility. These
unique properties allowed the team totransform the myoblast-coated films
into tubular assemblies — without
damaging the cells — by rolling themaround a soft silicone tube, showcasing the potential of using the nanomembranes as scaffolds in complex
tissue architectures.
The team is currently investigating
how they can apply these findings to thedevelopment of flexible biodevices andtissue regeneration. “The system will be
useful for mimicking blood vessels or
investigating tissue responses to various
drugs and toxic chemicals using lab-ona-chip devices,” says Fujie.
1. Fujie, T., Ahadian, S., Liu, H., Chang, H.,
Ostrovidov, S., Wu, H., Bae, H., Nakajima, K.,
Kaji, H. & Khademhosseini, A. Engineered
nanomembranes for directing cellular organization toward flexible biodevices. Nano Letters13, 3185–3192 (2013).

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RESEARCH HIGHLIGHTS

Raman spectroscopy

Pairing up for mercury detection
An extremely sensitive nanoporous gold-based optical sensor improves thedetection of mercury ions in drinking water

AIMResearch 2013

Cy5-labeled
aptamer

Modified, with permission, from Ref. 1 © 2013 American Chemical Society

Mercury enters drinking water froma number of sources, including theerosion of natural deposits, wastewater
discharged from oil refineries andrunoff from landfill and agriculturalland. As its accumulation in humans
can cause irreversible damage to thebrain and central nervous system, thelevels in water are closely monitored.
“Although many methods have beenreported, developing a quantitative
approach capable of detecting subpart-per-trillion levels of mercury ionswith high selectivity is still challenging,”
explains Ling Zhang from the AIMRat Tohoku University. Zhang, Mingwei
Chen, Qi-Kun Xue and co-workers have
now designed a nanoporous gold-based
optical sensor that is around 1,000 times
more sensitive than conventional
optical methods1. “This is the mostsensitive optical sensor for mercury
ion detection in water known so far,”
Xue says. “The US Environmental
Protection Agency’s limit for mercury
ions in drinking water is 10 nanomoles
per liter, and the detection limit of oursensor is 10,000 times lower.”
The team’s sensor utilizes the technique of surface-enhanced resonanceRaman scattering (SERRS). Like Raman
spectroscopy, SERRS relies on the factthat every molecule scatters light differently — an effect that can be weakand difficult to detect. To overcome
this issue, the Raman signal is amplified
in two ways. First, a roughened metal
surface — in this case nanoporous
gold — is used. A laser excites the gold’s
surface plasmons, which increases thesurrounding electric field. As Raman
scattering intensities are proportional tothis electric field, the signal is therefore

Nanoporous
gold surface

Mercury ion

Within the sensor, mercury ions cause aptamers to bind together in pairs, pulling the cyanine 5 (Cy5)fluorescent tags away from the gold surface and therefore changing the intensity of the Raman signal(inset graphs).

amplified. Second, the excitation wavelength of the laser is matched to theabsorbance of the molecule being analyzed. Thus, the laser light is absorbed,
further amplifying the signal.
In the researchers’ study, the fluorochrome reporter molecule cyanine 5(Cy5) is detected, rather than the mercury ion itself. Their sensor comprises
flexible, single-stranded aptamers thatare tagged with Cy5 and immobilizedon the gold surface. Mercury ions,when present, bind to adjacent aptamers, pairing them to produce relatively
rigid duplex-like structures (see image).
This pulls the Cy5 tags up and awayfrom the gold, resulting in a measurable reduction in the SERRS signal.

At higher mercury concentrations, agreater number of aptamers are boundtogether, which further reduces the
SERRS signal.
“Having successfully detected mercury ions in river water and undergroundwater,” says Chen, “we are now working
on the design and fabrication of a microchip that can be used in conjunction
with a portable Raman spectrometer for
real-world in situ detection.” The teamis also looking to tweak the aptamers totest for other heavy metal ions.
1. Zhang, L., Chang, H., Hirata, A., Wu, H.,
Xue, Q.-K. & Chen, M. Nanoporous gold based
optical sensor for sub-ppt detection of mercury
ions. ACS Nano 7, 4595–4600 (2013).

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RESEARCH HIGHLIGHTS

Graphene oxide

Responding to infrared light

Photodetectors, especially those that sense
the infrared region of the electromagnetic
spectrum, are important devices with uses
in optical communication and imaging
instruments. They rely on the generationof negative and positive charges — electrons and holes — by optical excitation.
Subsequently, the charges are separated
and contribute to an electrical current.
However, in graphene, a material wellknown for its exceptional electronic
properties and the foundation of several
established photonics components, theelectrons and holes rapidly recombine.
As a result, the amount of photocurrent
that can be generated from a watt of incident radiation — the photoresponse — isvery low, and preparing a graphene-based
photodetector has remained a challenge.
Now, Haixin Chang, Hongkai Wu,
Mingwei Chen and Yuichi Ikuhara fromthe AIMR at Tohoku University andco-workers have demonstrated the possibility of enhancing the infrared photoresponse of graphene oxide, a close relativeof graphene, by controlling the structureand number of defects in the material1.
Chang’s team began by reducing
few-layered graphene oxide throughthermal annealing to improve its electronic properties. Then, they studied thestructure and type of defects found in theoriginal and reduced graphene oxide withtransmission electron microscopy and
X-ray photoelectron spectroscopy. While
the original material contained large domains of highly ordered and disordered
lattices (see image), thermal annealing
decreased the size of both of these areas
and also affected the nature of the oxygencontaining groups.
The researchers were able to directly link the structural modifications

20

Reproduced, with permission, from Ref. 1 © 2013 American Chemical Society

Efficient infrared photodetectors can be fabricated by controlling the atomic
structure and number of defects in graphene oxide

Transmission electron microscopy image of graphene oxide, containing large regions of high disorder (yellowline) and order (blue line).

introduced during thermal annealing
to changes in the few-layered graphene
oxide’s photoresponse. Under infrared
illumination, the team observed a photocurrent signal in the thermally annealed
material that increased with the length ofannealing — something they could notdetect in the original.
Next, the team fabricated flexible infrared photodetectors from the reduced
few-layered graphene oxide, finding thephotoresponse of the devices to be overan order of magnitude higher than thatof devices made from pristine graphene.
The external quantum efficiency, a measure of the number of electrons and holes
created by each photon under externalbias, reached 97% — among the highest
observed in graphene-based infrared
photodetectors. Furthermore, the devices

were very stable, retaining their photoresponse after 1,000 bending tests.
According to Chang, these findings
could provide new ways to control the optoelectronic properties of graphene-based
and other two-dimensional systems. His
team is currently working to improve theresponse time of the reduced graphene
oxide, which is still quite slow. “We believe that there are further opportunities
to improve the photoresponse by further
optimizing defects and atomic structures,”says Chang.
1. Chang, H., Sun, Z., Saito, M., Yuan, Q., Zhang, H.,
Li, J., Wang, Z., Fujita, T., Ding, F., Zheng, Z.
et al. Regulating infrared photoresponses in
reduced graphene oxide phototransistors by
defect and atomic structure control. ACS Nano
7, 6310–6320 (2013).

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RESEARCH HIGHLIGHTS

Spintronics

Using nature’s symmetries

Symmetry is an important concept thatmust be taken into account to explain
the properties of the Universe, as well as
those of molecules and atomic crystals.
Researchers from the AIMR at Tohoku
University, together with collaborators from Osaka University, have now
shown how the symmetry of crystalsof tin telluride (SnTe) can be modified
such that the material demonstrates
various electronic effects1,2.
Tin telluride is a conventional semiconductor with commercial applicationsin infrared photodetectors. A featureof the compound is that its crystals are
mirror-symmetric, meaning that they
do not change upon reflection. As aconsequence, the electronic states atthe surface of the crystal are protectedagainst perturbations. Such crystals areclassed as topological crystalline insulators and exhibit ‘topological states’ on
their surface.
A practical advantage of these topological states, explains Seigo Souma, amember of the research team, is that thematerial’s electrical conductivity is independent of size. “Normally, when we reduce the size of the conducting material,
at some point electrons cannot move andthe material becomes insulating. This isa real limitation when down-sizing electronic devices. However, materials with
topological protection could overcome
such limitations.”
In tin telluride, topological states canbe controlled by changing the atomic
composition of the crystal. Souma andhis colleagues replaced some of thetin with lead, discovering that when
the lead content was 75% or higher,
the topological states disappeared1(see image).

AIMResearch 2013

Reproduced from Ref. 1 © 2013 American Physical Society

The different fundamental symmetries of tin telluride make it an ideal testing
ground for the study of topological states

The surface of the topological crystalline insulator tin telluride (SnTe) has electronic states (pink) that differ
from those in the interior (yellow: Sn or Pb; green: Te). When the lead (Pb) content of the crystal is increased(left to right), these surface states disappear as the character of the interior becomes inverted.

As well as destroying these states,
the researchers also found that they
could alter them. When they replaced alow percentage of the tin with indium
instead of lead, the samples became
superconducting at low temperatures.
Owing to the symmetries of themodified crystal, the resulting material,
Sn1-xInxTe, is a rare form of a topological superconductor2. Interestingly,
topologicalsuperconductors
arepredicted to contain an unusual classof particle known as a Majorana
fermion. As their own anti-particle,
these fermions possess some uniqueproperties and are very stable to external
perturbations, making them appealingfor use in electronic applications.
Souma notes that with the ability tocontrol symmetries and topologicalstates through atomic substitution, newpossibilities arise — including further
investigation into the existence of the

Majorana fermion. “One interesting future possibility is to create thin layers oftin telluride/lead telluride in a device.
As topological states do not only exist
at the surface, but can also arise at theinterface between a topological and an
ordinal material, one can encapsulate
the topological state between these
two layers.”
1. Tanaka, Y., Sato, T., Nakayama, K., Souma, S.,
Takahashi, T., Ren, Z., Novak, M., Segawa, K. &Ando, Y. Tunability of the k-space location of
the Dirac cones in the topological crystalline insulator Pb1-xSnxTe. Physical Review B
87, 155105 (2013).
2. Sato, T., Tanaka, Y., Nakayama, K.,
Souma, S., Takahashi, T., Sasaki, S., Ren, Z.,
Taskin, A. A., Segawa, K. & Ando, Y. Fermiologyof the strongly spin-orbit coupled superconductor Sn1-xInxTe: Implications for topologicalsuperconductivity. Physical Review Letters
110, 206804 (2013).

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RESEARCH HIGHLIGHTS

Molecular magnets

Mathematical predictions

Molecular magnets can be handled likeclassical particles owing to their relatively
large size, but they also exhibit quantum
magnetic properties thanks to their
unpaired electron spins. This uniquebehavior makes them attractive as highdensity information storage materials
and for spintronic-based computing.
Currently, chemists struggle to attach
molecular magnets to device surfaces,
however, because these particles have atendency to warp and lose their magnetic
properties on adsorption.
To overcome this difficulty, an international team led by Daniel Packwood
from the AIMR at Tohoku University has
now developed innovative ‘mathematicalchemistry’ techniques that can predict
novel molecular magnets with deformation-resistant magnetic moments1.
Most molecular magnets are madeby linking transition metals, such as
manganese and iron, into complex
clusters through hydrocarbon or oxygen‘bridges’ (see image). When the couplinginteractions between the unpaired metal
ion electrons within these metal–organic
complexes are strong enough, the molecules acquire an appreciable magnetic
moment. Packwood and colleagues hypothesized that the intimate relationshipbetween structure and magnetic behavior
in these systems could mean that certain
geometric networks, currently unknown
to chemists, exist with intrinsically stablespin properties.
To find these structures, the researchers devised an original model thatexamines how one physical property— the energy of the molecule’s groundspin state — changes with small, random
shape deformations of a molecularmagnet. “Creating a realistic model

22

Reproduced from Ref. 1 © 2013 The Royal Society

Mathematical analysis points to how robust nanomagnets can be made fromsurprisingly small metal–organic complexes

Deformation

A molecular magnet containing twelve manganese ions (top) is modeled with a new mathematical approach(bottom left) that randomly deforms the structure to predict spin arrangements that give highly stable
magnetic moments (bottom right).

of a molecule is not so difficult,” says
Packwood. “However, the key challenge
is striking a good balance between physical realism and sufficient simplicity formathematical treatment.”
The team’s analysis showed that twodimensional molecules containing a sufficient number of spin centers can possess
extraordinarily stable ‘weak topologicalinvariant’ magnetic moments. “Whenmathematicians talk about topologicalinvariants, they usually mean properties
that don’t change under arbitrary stretching or squeezing deformations,” explains
Packwood. “A weak topological invariant is similar; however, it can change
under deformations that have a very low
probability of occurring. This difference
significantly broadens the applicabilityof the topological invariance concept tostudying real systems.”

Surprisingly, the researchers’ calculations showed that only between 20 and
50 spin centers were needed for a two-dimensional molecule to achieve robust andstable magnetism. They also found that
resistance to shape deformations improved
when the number of ring-shaped networks
in the model was kept to a minimum. As
the structures predicted by this joint mathematics–materials science study are wellwithin the size range of existing molecularmagnets, Packwood and colleagues are
confident that they represent practical targets for future chemical synthetic efforts.
1. Packwood, D. M., Reaves, K. T., Federici, F. L.,
Katzgraber, H. G. & Teizer, W. Two-dimensional
molecular magnets with weak topological invariant magnetic moments: Mathematical predictionof targets for chemical synthesis. Proceedings of
the Royal Society A 469, 20130373 (2013).

AIMResearch 2013

RESEARCH HIGHLIGHTS

Batteries

The power of patterns
Atomic-scale images reveal that ordering patterns on lithium cathode surfaces canstrongly influence battery performance

AIMResearch 2013

Li

Co

O

Modified from Ref. 1 © 2013 American Physical Society

Lithium (Li) ions, which are small
and light, are ideal for shuttlingcharge between cathodes and anodes
in rechargeable batteries. But despite
their widespread use, researchers still
struggle to understand the atomic
processes behind their movements atbattery interfaces. Now, Katsuya Iwaya
from the AIMR at Tohoku University
and collaborators have captured unprecedented images of surface atoms
on lithium cobalt oxide (LiCoO2)1, an
energy-rich cathode material.
In its bulk crystalline state, LiCoO2
has a structure consisting of alternating layers of lithium and cobalt oxide(CoO2). This arrangement allows
lithium and cobalt atoms to undergointeractions that determine the material’s electronic activity. Understanding
how these atoms arrange at cathode surfaces is difficult, however, because thebehavior of lithium ions depends on thematerial’s composition and can eludedetection with traditional microscopes.
To resolve this problem, Iwaya andhis team turned to the atom-resolved
imaging capabilities of scanning tunneling microscopy (STM). Normally,
STM requires atomically flat surfaces
to produce useful data — a challenge
when investigating LiCoO2 surfaces
due to their often polycrystalline andbumpy nature. The team devised a way
to synthesize single crystals of LiCoO2
with a controllable lithium content thatthey systematically changed. Peelingthese crystals apart in ultrahigh vacuum
conditions produced contaminant-free,smooth surface layers.
STM experiments revealed an abundance of atomic organization patternson the cathode surface (see image). In

The surface of crystalline lithium cobalt oxide (LiCoO2) contains a ‘triangle’ (red) of lithium atoms that forms
part of a hexagonal array (left and top right). Scanning tunneling microscopy (right) also reveals othersurface structures (ordered and disordered: middle and bottom right, respectively), which modify lithium-ion
battery efficiency.

some areas, they saw hexagonal arraysof lithium atoms that scattered awaywhen the researchers changed the voltage on the STM tip. Mostly though,they found cobalt oxide regions witheither ordered or disordered structures.
Depending on the degree of order inthe cobalt oxide, the conductivity ofthe surface electronic states varied
from insulating to metallic — a significant change from LiCoO2’s bulk
crystalline properties.
By comparing the STM results toquantum chemical simulations, theresearchers deduced that the unusual
surface properties of their cathodes
arise from non-uniform concentrationsof lithium ions. In turn, this produces
distinct ordering patterns that significantly modify surface electronic states.

“These ordering patterns are closely
related to diffusion of lithium within
the crystal,” says Iwaya. “Understanding
these processes in detail could lead tolithium-ion batteries with larger capacities and shorter charging times.”
Iwaya notes that these findings may
also help to develop novel atomic-scale
devices. “Because we can likely remove
individual surface lithium ions with the
STM tip, we can tune the surface electronic states at the nanoscale by controlling their ordering patterns — a potential
route to very small electronic circuits.”
1. Iwaya, K., Ogawa, T., Minato, T., Miyoshi, K.,
Takeuchi, J., Kuwabara, A., Moriwake, H., Kim, Y.
& Hitosugi, T. Impact of lithium-ion ordering on
surface electronic states of LixCoO2. PhysicalReview Letters 111, 126104 (2013).

23

RESEARCH HIGHLIGHTS

Superhard materials

Shear resolution

Boron carbide (B4C) is a superhard yet
lightweight ceramic material. As a resultof these characteristics, it is used as aprotective component in bulletproof vests
and tank armor and also has many otherindustrial applications. Despite its hardness, boron carbide’s crystalline structure
deforms under shear pressure, which
creates amorphous regions that lead tothe failure of the material. The precise
mechanism behind this destructive amorphization, however, remains unclear.
Now, Mingwei Chen, Madhav Reddy
and colleagues from the AIMR at Tohoku
University have used Cs-corrected scanning transmission electron microscopy(STEM) to investigate the atomic-level
deformation processes that take place
during the formation of amorphous
shear regions in boron carbide1.
“Understanding such processes is important for the design and developmentof new boron carbide-based materials
with improved impact performance,”says Chen. “It is also important for understanding the basic failure processes ofa covalent material.”
The crystalline structure of boron carbide comprises 12-atom icosahedra and3-atom carbon–boron–carbon chainslocated within individual crystal planes.
Under shear pressure, amorphous bands
approximately 2 nanometers wide are
created, which form within the plane
containing the carbon–boron–carbon
chains (see image).
Using a technique known as annularbright-field (ABF) imaging, which allows light elements to be observed athigh spatial resolutions, Chen and hiscolleagues probed the finer details of theshear bands. The researchers were able
to identify atomic-scale changes, which

24

Reproduced, with permission, from Ref. 1 © 2013 K. Madhav Reddy et al.

Microscopic analysis reveals the atomic structure of amorphous shear bands inboron carbide

When boron carbide (boron: red spheres; carbon: blue spheres) is subjected to shear pressure (red arrows),
amorphous regions (yellow) form in the plane that contains the 3-atom carbon–boron–carbon chains.

led them to conclude that the shear
bands were formed from disassembly of
the icosahedra.
At the interface of the crystalline regions and the amorphous zone, the teamobserved deformed icosahedra. Whilesome icosahedra were displaced fromtheir original position by a considerable
distance, others were hardly displaced atall, indicating that the conversion froma crystalline to an amorphous structure
is progressive within the material. In theamorphous band, the icosahedra were irregularly shaped, randomly located andalso lower in number than in the bulkof the material. The latter may either be
due to the collapse of icosahedra during
shear band formation or limitations of

the ABF-STEM imaging technique whenobserving tilted icosahedra.
“Our findings could help to fabricateboron carbide materials with improved
mechanical properties by reinforcing
atomic chains through chemical doping
or changing the boron/carbon ratio,” says
Chen. “We are now focusing on structuralcharacterization and modification of theatomic chains in boron carbide by utilizing advanced Cs-corrected STEM anddeveloping boron-rich boron carbide andheavily doped boron carbides.”1. Madhav Reddy, K., Liu, P., Hirata, A.,
Fujita, T. & Chen, M. W. Atomic structure ofamorphous shear bands in boron carbide.
Nature Communications 4, 2483 (2013).

AIMResearch 2013

IN THE SPOTLIGHT
The AIMR has grown rapidly since its inauguration in 2007, now
with over 140 leading researchers from all over the world, including
31 internationally renowned principal investigators who are charged
with pioneering new and innovative breakthroughs in materials science.
The institute is also active in developing young, promising researcherswith a focus on strong cross-disciplinary collaboration and creativity.
AIMResearch spotlights these talented researchers of the present andfuture, detailing their daily research activities and scientific ambitions.

IN THE SPOTLIGHT

Published online on 28 January 2013

RESEARCH SUPPORT FOCUS

Comprehensive support forworld-class research
In recognition of its researchers’ efforts to successfully bridge the gap between mathematics and many different
areas of materials science, the AIMR is committed to creating the most conducive environment for research andcareer building

S

ince its establishment in 2007, theAdvanced Institute for Materials
Research (AIMR), as one of theinaugural research institutes of the World
Premier International Research Center
Initiative (WPI), has consistently maintained a contribution to society throughthe creation of new and innovative materials. A highlight among the AIMR’s many
remarkable achievements is the creation ofa pilot cross-disciplinary research programthat brings together materials science andmathematics-related fields. This approach,dubbed ‘fusion research’, has the materials
science community abuzz with its important discoveries.
Reflected in accomplishments so far,the success of the AIMR can be attributed

to its team of more than 130 researchers
who cover the areas of materials science,physics, chemistry, engineering andmathematics. Going forward, the AIMR
has pledged to inaugurate an even more
attractive and robust support system for
its researchers. “We have gained a lot ofinvaluable experience since the AIMR was
established five years ago. We are now in
an ideal position to build on our foundation and to offer the best support for all
our researchers in recognition of their
hard work,” affirms Susumu Ikeda, deputy
administrative director of the AIMR.
The AIMR has identified several key
areas of difficulty that a new team member
or a visiting foreign researcher may facewhen they first embark on their research

The Common Equipment Unit was set up to allow open access to essential apparatus, such as electron
microscopes and a photoemission spectrometer, for all researchers at the AIMR.

26

within the institute. In tailoring a comprehensive system to address those issues,suggestions from current staff members
were analyzed together with studies of theorganization and its facilities. The resultof this extensive planning and implementation period was the opening of the
Research Support Center, which consistsof four divisions: the Common Equipment
Unit, the Computation-Aid Unit, theMathematics Collaboration Unit and the
Researcher Support Office.
Access for everyone
In contrast to most overseas universities
and research institutes, where access tocommon facilities and instruments iseasy and guaranteed, experimental equipment usually belongs to an individuallaboratory. New team members or visiting
researchers may therefore find it difficult
to gain access to equipment without formal collaborations. To address this issue,
the Common Equipment Unit was set
up to establish common facilities thatoffer essential apparatus such as electron
microscopes, X-ray diffractometers and aphotoemission spectrometer. Instruments
located in associated institutions are also
made available. “The Common Equipment
Unit has since fulfilled many requests,
from finding a specific piece of equipment,
to designing appropriate experiments andproviding training in English,” says Ikeda.
Ensuring a smooth start
The innovative strategy of bringing together different areas of materials science
with mathematics requires intensive theoretical studies and numerical calculations.

AIMResearch 2013

IN THE SPOTLIGHT

At the Common Equipment Unit, staff members with fluency in both Japanese and English are available to assist
with the design of experiments and provide training for AIMR researchers.

Correspondingly, the AIMR understands
that an adequate and efficient infrastructure is crucial for supporting research ofsuch magnitude. The Computation-Aid
Unit is designed to offer a platform forthe seamless inception of new projects.
Operated by in-house theoreticians, theComputation-Aid Unit is particularly
beneficial to newly appointed members ofstaff and visiting researchers. “Together,
the Common Equipment Unit andComputation-Aid Unit provide support
not only to the initial phase of a research
project, but also extend continual support to ensure a successful outcome,”
explains Ikeda.
Unifying materials scienceand mathematics
Traditionally, materials science researchhas been largely empirical and involved agreat deal of trial and error. By contrast,
mathematics concerns the setting ofclearly-defined parameters, followedby the building and testing of theories.
While the gap between the two fields has
been bridged significantly over the last
five years, ongoing effort is necessary tomaintain the bond. The Mathematics
Collaboration Unit was established to promote effective communication between
AIMR materials scientists and mathematicians, and to encourage interactions withexternal mathematical communities.
So far, the Mathematics Collaboration
Unit has already made significant effort

AIMResearch 2013

toward connecting the AIMR with theApplied Mathematics Forum at Tohoku
University; since the first joint seminarin June 2012, three more similar sessions
have been organized to further strengthen
the relationship.
Extending a helping hand
The AIMR appreciates that even themost gifted researchers may need assistance to advance their scientific career.
Furthermore, AIMR staff members may
also experience personal or family issues
from time to time. In line with its commitment to ensuring staff well-being,
the AIMR commissioned the Researcher
Support Office — the fourth unit of the
Research Support Center. “To equip young

scientists with competent writing skills,
the Researcher Support Office facilitatedan advanced scientific writing and publishing workshop conducted by Macmillan
Science Communication,” says Ikeda. In
addition, a mentoring system was initiatedto enable younger researchers to connect
with more established senior researchersand gain assistance with the importantcomponents of building a strong research
career. Support is also available for administrative matters such as grant applications,working visa applications and renewals,
and any other issues concerning daily life.
“The AIMR knows it is important for foreign researchers to settle into their life in
Sendai. We strive to provide all necessary
support and assistance to make that transition a smooth one. A Researcher Support
Office can be found in every building,”
assures Ikeda.
Moving toward world-class status
With the new Research Support Centerin place, present and future membersof staff at the AIMR will undoubtedly
find themselves in an environment thathas a remarkable level of comprehensive
support for the realization of their fullpotential and goals. Embarking on thenext stage of its development, the AIMR istherefore set to continue attracting exceptionally talented individuals from all over
the world, putting it on track to become aworld-class research institution that offers
both an excellent forum for research andan ideal working environment.

The Mathematics Collaboration Unit organizes joint seminars at which materials scientists and mathematicians
can interact to benefit from each other’s expertise.

27

IN THE SPOTLIGHT

INTERNATIONAL SYMPOSIUM

Published online on 25 March 2013

Materials and math makes green
The AIMR International Symposium 2013 — convened by the AIMR in Sendai, Japan on 19–21 February 2013 —showcased cutting-edge research from leading international materials scientists and demonstrated how the power ofmathematics is being harnessed to drive green innovation

S

ince its launch in 2007, the AIMR
has built an enviable reputation
for innovative fusion research inmaterials science, bringing together top
international researchers in disciplines
such as bulk metallic glasses, materials
physics, soft materials and devices andsystems. In 2012, a fifth research grouping — Mathematics Unit — was added,
beginning a new chapter in the institute’s
scientific development.
Held since 2008, the annual workshop— renamed as the AIMR International
Symposium — provides a forum for AIMR
researchers, including those based overseas, and other internationally renownedmaterials scientists to discuss the latest developments in the field. The sixth symposium was held at the Sendai International
Center from 19–21 February 2013 underthe banner theme of “Challenge for green
materials innovation through the fusion ofmaterials science and mathematics,” anddrew more than 240 participants from
14 countries.
In contrast to previous years, themeeting attracted a significant number ofattendees and four speakers from the fieldof mathematics, mirroring the recent focus
on mathematics-driven materials scienceat the institute. AIMR director Motoko
Kotani, herself a distinguished mathematician, welcomed the development
but pointed out that it reflected a natural
evolution of the profile of the center. “We
included a session on mathematics andcomputational science and one mathematician in the opening session but that wasall,” she said of the inaugural workshop.
“[This year], as in previous years, wecalled for recommendations of speakers
from our researchers, and chose the best28

from the list. I myself was surprised to findso many talks with mathematical hints inthe symposium program. This shows ourmathematics-driven materials idea has
captured the imagination of our members.”
The decision to place mathematicsdriven materials science at the heart of the
AIMR’s research strategy was announced
by Kotani at the 2012 workshop, and theinitiative has gained form and momentum since then. “I explained our idea of
math–materials science collaboration toaccelerate interdisciplinary research at theconclusion of the workshop last year,” explained Kotani. “But at the time, although
we were confident we made the rightdecision, our ideas for the collaboration
were then still largely unformed. In theintervening period, through much discussion and consultation, we have establishedthree target projects to give a concrete
strategy to our idea, and worked intensively to pursue research in this direction
for one year.” While acknowledging that itis still too early to claim that the AIMR’s
mathematics–materials science collaborations have met the challenges of “green
materials innovation,” Kotani remarked
upon the encouraging initial results due tobe presented at the 2013 symposium.
This year’s meeting was opened by
Susumu Satomi, president of Tohoku
University, who extended a formal welcome to the delegates and congratulated
AIMR members on their developmentof world-class research programs. This
achievement, and the research-first, practice-centered ethos of Tohoku University,
has ensured that the AIMR continues toplay a central role in the life of the university, he said. Further development of
the institute would be strongly influenced

Tohoku University President Susumu Satomi formallywelcomed delegates to the AIMR International
Symposium 2013, which focused on the theme of“Challenge for green materials innovation throughthe fusion of materials science and mathematics”.

by the success of the newly established,mathematics-driven materials science
framework. Pledging the continued support of the university, the president also
praised the international character of the
AIMR and paid tribute to the role playedby the institute’s 19 overseas partners, and3 satellite institutions at the University ofCalifornia, Santa Barbara in the US, theChinese Academy of Sciences’ Instituteof Chemistry and the University ofCambridge, UK.
Welcoming delegates to the symposium, Toshio Kuroki, program director of
the World Premier International ResearchCenter Initiative (WPI), which oversees
the operation of the AIMR, reiterated
the importance of mathematics-driven
materials science research to the institute’s
work. Introducing the mathematics–materials approach had given the AIMR a “newAIMResearch 2013

IN THE SPOTLIGHT

Nobel laureate Ei-ichi Negishi, from Purdue
University in the US, discussed his research into
zirconium-catalyzed addition reactions.

culture and paradigm shift,” in addition toa distinctive focus that complements thealready high levels of research achievement established since its inception in
2007, Kuroki said.
In her symposium address, Kotani
restated the institute’s goal to integrate materials science with physics, chemistry andengineering to create new materials thatcan contribute to society. Although a worthy and important aim, achieving this has
not proved easy, Kotani noted. Working
through the original AIMR launch plan
had led to the realization that it wasnecessary to take greater account of themathematical view of the field, she said.
Further consideration had identified threetarget projects: Non-equilibrium Materials

based on Mathematical Dynamical
Systems, Topological Functional Materials,
and Multi-scale Hierarchical Materials
based on Discrete Geometrical Analysis,that now form the mainstay of research at
the AIMR. Kotani also spoke of the importance of the AIMR as an incubator forinternational research talent and encouraged researchers from around the world tojoin the AIMR’s research programs.
Following the introductory addresses,
the conference’s academic program
began with a special opening lecture
entitled “The Magical Power of Transition
Metals: Past, Present and Future” by
Ei-ichi Negishi from Purdue University
in Indiana, US. Negishi, who shared the2010 Nobel Prize in Chemistry for his
work on transition metal-catalyzed crosscoupling reactions, gave a wide-ranging
survey of his research into zirconiumcatalyzed addition reactions and spoke ofhis belief in the importance of transitionalmetal chemistry for future developments
in materials science.
The session continued with a lecturefrom Hideo Ohno, a principal investigator at the AIMR who presented thelatest developments in ferromagnetismin semiconductors. Ohno was the 2012
recipient of the IEEE David Sarnoff
Award — seen by many in the field as aprecursor to the award of the Nobel Prizein Physics — and is also director of theCenter for Spintronics Integrated Systems
at Tohoku University. The opening session
concluded with lectures from Masakazu
Aono, director of the International
Center for Materials Nanoarchitectonics(MANA) — one of the original nine WPI
institutes — who provided an extensive
assessment of recent topics in materials
nanoarchitectonics, and Shun-ichi Amariof the RIKEN Brain Science Institute
who drew parallels between the modern
differential geometrical analysis of neuralnetworks and nanomaterials.
Plenary sessions featured lecturesin mathematics and computation,
spintronics, and processes and functiondelivered by delegates from Switzerland,
Japan, Poland, Germany, the UK and
the US, representing the research andgeographical diversity of the meeting. In
total, 32 lectures divided into 10 plenary
and parallel sessions were presented during the symposium, supplemented by a
2-day poster session featuring 90 contributions from both Japanese and international
AIMR researchers.
The AIMR International Symposium2013 concluded on 21 February with closing remarks from Masaru Tsukada, administrative director of the AIMR, in which
he thanked the organizers, speakers andparticipants and extended an invitation
to all present to join the next symposiumin 2014.

The symposium attracted 240 delegates, including a significant number of attendees and four speakers from the field of mathematics.

AIMResearch 201329

IN THE SPOTLIGHTFEATURED RESEARCHERS

Published online on 29 July 2013

Scaling the heights of materials
science research
Akari Takayama is a 2013 recipient of the exclusive JSPS Ikushi Prize for research excellence, awarded for her PhD
work as part of the AIMR Materials Physics Group

E

stablished in 2009 with an endowment from Emperor Akihito toencourage and support young
scientists, the Japan Society for the
Promotion of Science (JSPS) Ikushi
Prize has been awarded annually to
16 outstanding early-career researchers
in the natural and social sciences since2010. Akari Takayama, currently a JSPS
research fellow in the Materials Physics
Group at the Advanced Institute forMaterials Research (AIMR), speaks to
AIMResearch about her recent award, herresearch, life at the AIMR and her plans
for the future.
AIMResearch: Congratulations on winning the JSPS Ikushi Prize in 2013. How
did you learn that you had won the prize?
I found out about it at the end of
December when I passed the initial examination meeting of my doctoral thesis.
I was talking through my progress andresults when my PhD supervisor [Takashi
Takahashi, a principal investigator in the
Materials Physics Group] gave me thenews. The moment I heard I’d won the
prize, I was very surprised. Initially, I
couldn’t believe it but when it sank in, I
was so happy and honored.
We were actually having a belated lab
Christmas party at the time. We ate thecake as a sort of unofficial celebration
since the lab was sworn to secrecy — theprize results had to be kept under wraps
until the official announcement in January.
However, I did get to tell my parents.
AIMResearch: The Ikushi Prize is only
presented to a small number of top young

30

Akari Takayama, a 2013 recipient of the JSPS Ikushi Prize for research excellence.

scientists in Japan every year. What effecthas winning this award had on your career
so far?
I won the prize for my work as a PhD
student, which I carried out under the
direction of a supervisor. After receiving
the award I feel a responsibility to step up,
keep delivering even stronger results andmake my mark as a researcher in my own
right. However, the greatest immediatechange was probably that my researchbecame a lot better known. People now
come up to tell me that they have read mypapers and take an interest in my work,
which of course makes me very happy.
But more than the recognition, I value
the opportunity this gives me to interact
with other researchers, particularly thosefrom adjacent fields. I learn a lot fromthem and am inspired to look at thingsfrom a different angle and imagine different approaches.
AIMResearch: You achieved a tremendous
amount during your PhD studies. What do
you think has been the key to your success?
I think it helps that I’m a pretty observant
person. In my view, it’s really importantin scientific research to have an eye fordetail and to be able to notice subtle
changes that are out of the ordinary.
When developing equipment or optimizing an experiment, it is critical to be able
to spot what makes one condition different from a previous arrangement andwork out how this can be used to improvethe experimental outcome. Similarly,
when analyzing data, it’s vital to be able
to distinguish an unusual and potentiallysignificant result from an artifact.

AIMResearch 2013

IN THE SPOTLIGHT

I’m also somewhat of a perfectionist:
all the samples that I make in my research
have to be meticulously prepared. If mymaterials aren’t top quality, I won’t use
them. I’m proud of the quality of mysamples — I don’t want anyone to say mysamples are a bit substandard.
AIMResearch: Your PhD thesis discussed
the effects of spin polarization in materials, which is extremely important fortechnologies such as ‘spintronics’. Whatis spintronics, and how does your work
contribute to the field?
Spintronics involves trying to control andmanipulate the direction of the magnetic
moment, called ‘spin’, that is one of thefundamental properties of electrons.
One application for this technology is
to use it to store electronic information
as the basis for new types of computer
memory, which would be many times
smaller and more energy efficient thancurrent devices. But in order to control
these spins, we first have to be able tomeasure properties such as their size andthe direction in which they are pointing.
My work involves designing equipment and methods for measuring theseproperties very accurately, which can bequite challenging.
Thanks to the JSPS fellowship, I will
be able to extend my PhD work to othermaterials systems and to study their spinpolarization phenomena. My research has
discovered anomalous behaviors of spin,
and the results suggest a new possibilityof spintronics. To check the universalityof this discovery, I am eager to investigate
systems with different elements to the
one I have been studying, but which
theory suggests should display the samekinds of phenomena.
AIMResearch: What are the best things
about working at the AIMR, and what
attracted you to carry out your doctoral
research here?
There are many reasons to study at the
AIMR. You get to meet and work witha great number of extremely talented
researchers from different, but related,
fields and are therefore able to take

AIMResearch 2013

As a JSPS research fellow in the Materials Physics Group at the AIMR, Takayama is currently studying spinpolarization phenomena in materials as an extension of her PhD research.

advantage of their insight and ideas.
For example, I often interact with colleagues from the recently incorporated
Mathematics Unit at events such as theweekly Tea Time, and we have had many
useful and interesting discussions.
My interest in mathematics and mylevel of understanding has definitely
improved as a result, and I am sure thiswill have a positive impact on my workin the future. Plus, AIMR researchers
come from all over the world, which isenormously stimulating.
The facilities and the researchsupport provided by the AIMR are
truly excellent. Obviously, we have thenecessary equipment within our lab
to obtain high-quality data for experiments in our field, but with the kind ofadvanced, cross-disciplinary researchthat my group is performing, we often
need to look at our systems from different
experimental perspectives. Fortunately, at
the AIMR I have access to all the otherresources — both facilities and researchcollaborators — that I need, under
one roof.

AIMResearch: You have already achieveda great deal in your career. What are yourplans for the future?
I definitely want to stay in research,
but I don’t particularly feel the need to
become a famous professor. The part of
my research that I like best is designingand making new experimental equipment,
then using it to explore new materials
systems. The moment when I first obtainnew data is really exciting. I’d like to keep
working in an environment where I canpursue research and experience the thrillof discovery. I also want to try my handat other experimental techniques. Up tonow, I’ve specialized in photoemission
spectroscopy, but I’d really like to learn
new methods in order to evaluate thequality of samples more comprehensively.
Wherever I am and whatever methods I
use, I see myself always enjoying life as a
researcher, though I think that it is hard
to learn new techniques. For this reason,even small and incremental improvements
please me when I am making samples orsetting up machines.

31

IN THE SPOTLIGHTRESEARCH SUPPORT FOCUS

Published online on 30 September 2013

No bridge too far
The Interface Unit, which bridges the gap between mathematics and materials science at the AIMR, is helping totransform the way the institute thinks about research in both fields

W

hen the Advanced Institute forMaterials Research (AIMR)
embarked on its bold strategy
of applying a mathematics-driven approach to materials science researchunder the directorship of Motoko Kotani,
it faced a fundamental challenge: how toassist its mathematicians and experimental materials scientists — who respectively contend with abstract concepts
and very concrete problems — to speak acommon language.
To address this issue, the AIMR created the Interface Unit (IU), a group ofeight young theoretical physicists andchemists charged to act as a bridge between the institute’s mathematicians andresearchers from three Target Projects —Non-equilibrium Materials, Topological
Functional Materials and Multi-scale
Hierarchical Materials — chosen as test
beds for the mathematics-driven fusion
research approach. In addition to carrying out independent original research,members of the IU work closely with
their materials science colleagues to develop mathematical tools and models fortheoretical aspects of the Target Projects,
which subsequently guide the directionof experimental research. The radical
approach is not only influencing the waythat AIMR scientists tackle their work but
also has the potential to break the moldof interdisciplinary research.
Exploring new avenues
Miki Kobayashi, an assistant professor at
the AIMR who specializes in non-linear
dynamics, joined the IU in 2012. He admits to having had concerns at the outset
about the viability of the mathematicsdriven research strategy, which were
ultimately unfounded. “Materials scienceis a well-defined field that has achieved

32

Members of the AIMR Interface Unit (IU). Clockwise from top left: Miki Kobayashi, Masamichi Miyama,
Daniel Packwood and Koji Sato.

remarkable results without any special
involvement from the mathematical community, so I wondered if these researchers actually needed our help at all,” says
Kobayashi. “But I have been impressed by
how receptive my experimental researchcolleagues are to using mathematics
to explore new avenues in materials
research,” he adds. Masamichi Miyama, a
research associate in theoretical physics,
also joined the IU in 2012 and echoes
this sentiment. “When I started at the
AIMR, I had my doubts about whether
my background in statistical thermodynamics would be useful,” Miyama says.
“But my experimentalist colleagues havewelcomed our involvement, and I think
we work really well together,” he adds.
An important tactic used by the IU tobuild connections between the AIMR’s
mathematics and materials researchgroups has been to identify problems ofinterest to experimentalists that also havea mathematical ‘hook’. “It’s like a seed for
creating discussion from both sides,” says
Daniel Packwood, an assistant professor
and theoretical chemist who originallyhails from New Zealand. “Normally, experimentalists come to me with a problem then we discuss it further and I’ll goaway and work on it — and that may leadto publishable research.” This exchangeof ideas can work both ways, however,as the theoreticians often come up withmathematical concepts that may be ofinterest to the institute’s experimentalists.
Research without boundaries
Free discussion and collaboration areencouraged at the AIMR and channels
for interaction include weekly Tea Timesessions. In addition, there are regular

AIMResearch 2013

IN THE SPOTLIGHT

informal seminars aimed at stimulating
open-ended discussion where participants are encouraged to ask questions, nomatter how basic they may seem. “WhenI arrived at the AIMR, I was wary of approaching colleagues who were experts
in areas I knew very little about,” comments Koji Sato, a spintronics researcher
who joined the IU in early 2013. “At myprevious institution, it would have beendifficult for me to do this. But here, we
are under pressure — in a positive way —to collaborate, so I made up my mind
to not feel intimidated and to ask a lotof questions.”
Allowing members of the IU andexperimental researchers to interact
without boundaries has greatly improved
communication within the AIMR, although there is still a need for a degree of‘bilingualism’ on the part of IU members.
“I do find myself needing to use different
language depending on whether I am
talking to a mathematician or an experimental researcher,” admits Packwood. A
certain degree of individuality is inevitable — and even desirable — according to
Kobayashi. “We’re not trying to amalgamate maths and materials science. Our job
is to provide a bridge between the two.”Miyama agrees: “I would like mathematicians to retain their individual identity

but benefit from the different insight thatworking with materials scientists canbring.” Consequently, early concern about
the viability of the mathematics-driven
approach has largely been alleviated,
and the institute is now harvesting thefirst fruits of this strategy — in the formof a number of international conference presentations made by researchers
from the IU and papers jointly published with AIMR experimentalists inleading journals.
Breaking the mold ofinterdisciplinary research
The IU’s role in promoting efficientfusion research at the AIMR could also
serve as a model for other universities
and institutes — in Japan and around theworld — who are seeking to boost theirinterdisciplinary research programs.
“Given time, the AIMR could provide
a template for creating truly functioning interdisciplinary research,” says
Packwood. “We’re already producing innovative results that aren’t normally seenin the theoretical physics arena — but not
yet in the mathematical arena because
the results are so physical in character.
Nonetheless, you can’t just mix people
together and expect them to do interdisciplinary research. You need a catalyst.”

And while the IU provides exactly such a
stimulus, it is also helping to create a new
approach to research — one that is morepredictive and theory-led than typicalmaterials science, yet more descriptive
than traditional mathematics. “It’s important to be able to discover new thingsand develop new methods, especiallyin a mature field like materials science,”
notes Sato. “Hopefully our approach will
help to unlock new potential, although it
won’t be easy.”
Change is unlikely to come overnightand requires experimentalists andtheoreticians alike to work outside their
comfort zones, with the former accepting
a more structured approach to carryingout experiments and the latter being willing to relinquish a degree of theoreticalcompleteness. Although the potential
rewards for the AIMR and any resulting
interdisciplinary research are great, pushing forward with AIMR director Kotani’svision for mathematics-driven research
will take commitment, hard work andmore than a little courage. “The experimentalists are changing the way they doresearch,” observes Packwood, “and astheoreticians, so must we. It’s exciting,but it’s challenging. We have to learn tothink differently; maybe entirely new
types of approximation are needed.”

The IU is bridging the gap between mathematics and materials science researchers at the AIMR.

AIMResearch 201333

IN THE SPOTLIGHT

ROUNDTABLE INTERVIEW

Published online on 20 December 2013

Reaping the rewards ofa mathematics–materials approach
Founded in 2007 as one of the inaugural institutes of the World Premier International Research Center Initiative(WPI), the AIMR has now embarked on its second five-year term. In late 2011, the institute began an ambitious newmathematics-driven research strategy that is already delivering impressive results.

T

he mathematics-driven approachto materials science research at the
AIMR is a distinguishing feature of
the institute’s research culture and sets itapart from the other institutes in the WPI
program. Although still at an early stage,
the strategy has already produced a numberof exciting results. AIMResearch spoke to
Mingwei Chen, a principal investigatorin the Bulk Metallic Glasses Group, andMotoko Kotani, director of the AIMR anda principal investigator in the Mathematics
Unit, about their collaborative work which
was the subject of a recent Science paper.
AIMResearch: Your recent paper — entitled“Geometric Frustration of Icosahedron in
Metallic Glasses” — is an excellent example
of mathematics-driven materials science
research. How would you summarize thepaper’s main findings?
Chen: Our work presents conclusive evidence showing that metal atoms pack into
the glass state as geometrical fluctuationsof 20-faced units called icosahedrons. This
had previously been suggested, but we combined experimental results with extensivemodeling and simulation to confirm that
this motif could be used to make theoreticalpredictions of long-range disorder in metallic glass systems.
To understand structure–property
correlation in metallic glasses, we need towork on the atomic scale because, unlike
crystalline materials, glasses do not havea clearly defined microstructure, such as
grain or defects. This is extremely challenging because glasses essentially consistof long-range disorder. Uncovering the34

Mingwei Chen, a principal investigator in the Bulk Metallic Glasses Group.

atomic arrangement of glasses helps us togain insight into fundamental processes
such as the liquid to glass transition, theformation of shear transformation zones —the movement of atoms when force is applied — and the breaking of atomic bonds
and failure of the glassy material. The workin our latest Science paper1, which follows
our 2011 paper in Nature Materials 2,
establishes local structural features suchas the geometrical and topological atomic
arrangement and shows how these are
distorted in the glass state.
AIMResearch: Your discovery was achievedby combining experiment, theory and mathematical modeling. What respective roles didthese play in the research?

Chen: As you might expect, technicalaspects were extremely important in thiswork, and, in particular, the angstrombeam electron diffraction method. This
technique uses a modified transmission
electron microscope to precisely focus
a coherent electron beam of about
3 angstroms in diameter, without which wewould never have been able to observe thelocal atomic arrangement of the sample.
This is the first technique that allows us
to image not only metallic glasses but alsooxide glasses and other disordered systems
in such detail.
Kotani: A major part of the work involved
translating the experimental data intoa picture of the overall structure of the

AIMResearch 2013

IN THE SPOTLIGHT

metallic glass. This issue was addressedby Akihiko Hirata (associate professor
in the Bulk Metallic Glasses Group) and
Kaname Matsue (assistant professor
in the Kotani Laboratory) who usedadvanced topological methods to derivea global structure from local structural
data using a modeling program provided
by the C omputational Homolog y
Project (CHomP).
This web-based software provides
non-mathematicians with a relatively
pain-free way to analyze complicateddatasets using topological techniques. As
a result, many researchers at the AIMR
have become interested in using topology
to get essential data from complex figuresand hierarchies for working on glassy andnanoporous materials.
AIMResearch: The scientific value of thisresearch is very clear. What is its significancein terms of the mathematics-driven materials science agenda that has been adopted by
the AIMR?
Kotani: When we proposed the newmathematics–materials-driven research
approach, many thought it was an attractive
idea but also very challenging. What thatreally means is that they thought the strategy was rather high risk. I always believedthat the direction we chose was the correct

one but did not expect that we would get
concrete results so quickly. While I think weare yet to make a real breakthrough, results
like those in Professor Chen’s paper give us
confidence that our research program ismoving in the right direction.
Chen: I agree that it is important to havebeen able to prove the concept of combining mathematics with materials science insuch a short time. As an experimentalist,
I can say that working collaboratively
like this has not only given us a tool for
research, but has also changed our conceptual viewpoint and opened my eyes toa new research philosophy. Taking a more
fundamental approach, such as looking at
the topological interpretation of the system, has helped to keep our minds on the
bigger picture, as well as on the details.
AIMResearch: How do you expect the current collaboration to develop?
Chen: We believe that there is a common
link between the behavior of all types ofglassy materials and we are working toapply our methods to other systems suchas polymer and oxide glasses, as well as
chalcogenide glasses. Using theoreticalmodels derived from experimental data,
we can eventually begin to design materials
with enhanced properties.

Kotani: Gaining a comprehensive understanding of glassy substances is one of themain areas of work at the AIMR. In the
future, we will concentrate on establishinga universal framework for these systems.
Glassy materials exist at a phase interface
between particle dynamics, which obeys
certain mathematical rules, and continuum
dynamics, which can be described using
tools such as Navier–Stokes equations. At
the moment we do not have a master equation that describes these phenomena, so
developing a mathematical theory that canhandle these areas is a big challenge.
AIMResearch: How did the research
environment at the AIMR help to makethis discovery?
Chen: One important reason for the
success of our study is the way in which
the WPI program has fostered real fusion
research that, in the case of the AIMR, puts
mathematicians in the same building as experimentalists like me. This gives us the opportunity to discuss research directly, rather
than having to travel to different campuses,
and to establish working relationships withthe right people, straight away.
Kotani: I am also very grateful to the WPI
program for giving us the opportunity forthis kind of interaction and support. It
allows us to physically meet with the best
people to discuss problems on a daily
basis, which would not be possible under
any other system. The same commitment
to exchange has allowed us to set up theInterface Unit, which provides a bridge
between young independent researchers
in mathematics and experimentalists. The
system has really stimulated our young
academics and has provided a model that isbeing considered for roll out across Tohoku
University. As is apparent, this is a very
exciting time to be researching mathematics
and materials science at the AIMR.
1. Hirata, A., Kang, L. J., Fujita, T., Klumov, B.,
Matsue, K., Kotani, M., Yavari, A. R. & Chen, M. W.
Geometric frustration of icosahedron in metallic
glasses. Science 341, 376–379 (2013).

Motoko Kotani, director of the AIMR and a principal investigator in the Mathematics Unit.

AIMResearch 2013

2. Hirata, A., Guan, P., Fujita, T., Hirotsu, Y.,
Inoue, A., Yavari, A. R., Sakurai, T. & Chen, M.
Direct observation of local atomic order in a
metallic glass. Nature Materials 10, 28–33 (2011).

35

IN THE SPOTLIGHT

INTERNATIONAL WORKSHOP

Published online on 27 January 2014

Strengthening scientific exchange
and joint research
The AIMR represented Tohoku University and showcased some of its best science at joint workshops held with the
University of Cambridge and University College London in November 2013

W

hile the AIMR is well known
for its world-leading researchand international research
partnerships, the history of international academic exchange in Japan is still
relatively recent. The year 2013 marked
the 150th anniversary of the first Japanese
students — known as the Choshu Five —beginning their studies in England. In recognition of this milestone, UCL (University
College London) — the university that
hosted the students — organized a numberof commemorative events, including
several held in conjunction with Tohoku
University. The AIMR’s visit to the United
Kingdom offered a further opportunity foracademic exchange through a workshop on
mathematics and materials science at the
University of Cambridge.
Joint AIMR–University of Cambridge
workshop on mathematics andmaterials science
On 20 November, 14 researchers from the
University of Cambridge and 12 young
researchers from the AIMR convergedin Cambridge to attend the AIMR–
Cambridge Workshop and Discussion on“Hierarchical materials for green energy.”
The AIMR’s connection with the Universityof Cambridge was formalized in 2012,
when an agreement was signed to establish
an AIMR Joint Center (AJC) where UK
and AIMR scientists can perform joint
research into metallic glasses, soft materials
and mathematics.
Attendees at the workshop included
Alan Lindsay Greer, an AIMR principal
investigator and a professor at the Universityof Cambridge, and researchers Jiri Orava,
Katherine Orchard and Demeter Kiss from

36

The AIMR–UCL Materials Workshop focused on recent
developments in materials science.

the AJC in Cambridge. “The workshop
provided a relaxed atmosphere in which theyoung and promising researchers could holdintense discussions on mathematics andmaterials science,” noted Masaru Tsukada,
the administrative director of the AIMR.
Celebration of research with UCL
On 21 November, Tohoku University
signed a Memorandum of Understanding
with UCL to further promote scholarly
collaboration and international exchange,building on several years of successful scientific cooperation under academic exchange
agreements fostered between the AIMR,
two other institutions at Tohoku University
and UCL faculties. The signing ceremony
was followed by a forum to commemorate
150 years of academic exchange between
Japan and the United Kingdom, including speeches by eminent professors fromTohoku University and UCL. Representing

the AIMR, Director Motoko Kotani gave acommemorative address on the theme “AnIntroduction to the AIMR: Toward World
Premier Status and Beyond.”
The following day, a well-attended
AIMR–UCL Materials Workshop washeld. Focusing on recent developments
in materials science, the session featured
16 talks, including keynote lecturesfrom AIMR principal investigators (PI).
Alexander Shluger, a PI at the AIMR, expressed his expectations for future researchdevelopment, in consideration of the many
researchers — and potential collaborators — in attendance. “Each presentation
stimulated in-depth discussions, and we
expect further collaborations to develop as
researchers find common agendas.”Continued opportunities for exchange
The AIMR UK-based workshops proved
stimulating and provided researchers
located in Japan and the United Kingdom
with an opportunity to share research ideas
and findings. The workshops’ success is
expected to lead to further opportunities
for personnel exchange and joint research
projects, particularly in partnershipwith UCL. Additionally, the workshops
highlighted the value of promoting multidisciplinary exchange through AJCs at the
University of Cambridge and other AIMR
satellite institutions.
“I am pleased that the AIMR’s UK research activities are contributing to Tohoku
University and providing an opportunity tostrengthen its globalization efforts,” commented Director Kotani. “The AIMR and
Tohoku University have now establishedthemselves as top-class research institutes
with a firm base in the United Kingdom.”

AIMResearch 2013

Advanced Institute for Materials Research
Tohoku University