RIXS/REXS Workshop 2023
2nd–4th August 2023
Sakura Hall
Tohoku University

Book of Abstracts
Institute for Advanced Synchrotron Light Source
National Institutes for
Quantum Science and Technology

for Materials Research
IMR InstituteTohoku University

IMRT

Global Ins�tute forMaterials Research Tohoku-Interna�onal hub for collabora�ons in materials science-Wednesday, August 2nd-9:05

Registration
Chair: Masaki Fujita (IMR, Tohoku University)

9:05-9:20

Opening Remarks
Dr. Wataru Utsumi, Director of ASLS, QST
Prof. Takahiko Sasaki, Director of IMR, Tohoku University

Session Chair: Mark P. M. Dean (Brookhaven National Laboratory)
9:20-10:05

Ke-Jin Zhou (Diamond Light Source)

Spin and charge excitations in quantum materials probed by RIXS

Johan Chang (University of Zurich)
10:05-10:35 Magnon-magnon Interactions in Soft Mott Insulators
Yingying Peng (Peking University)
10:35-11:05 Charge order and its dynamics in overdoped Cuprates
11:05-11:35 BreakSession Chair: Thorsten Schmitt (Paul Scherrer Institut)
Di-Jing Huang (National Synchrotron Radiation Research Center)
11:35-12:05 Excitonic excitations of cuprate superconductors probed with high-resolution RIXS
Hiroyuki Yamase (National Institute for Materials Science)
12:05-12:25 Plasmon excitations and plasmarons in cuprate superconductors
12:25-13:30 Lunch
13:30-14:30 Poster session
Session Chair: Eugenio Paris (Paul Scherrer Institute)
Urs Staub (Paul Scherrer Institute)
14:30-15:15 Resonant Scattering to Study Ultrafast Dynamics of Spins and Electrons and theRelation to the Dynamics of the Lattice

Tsuyoshi Kimura (University of Tokyo)
15:15-15:45 Circularly polarized resonant x-ray diffraction of multiferroic CuOWilliam Windsor (Fritz Haber Institute of the Max Planck Society)
15:45-16:15 Towards control of ultrafast spin dynamics in 4f antiferromagnets
16:15-16:45 BreakSession Chair: Atsushi Hariki (Osaka Metropolitan University)
David Hawthorn (University of Waterloo)
16:45-17:15 Orbital/Nematic and Charge Density Wave Orders in Cuprate Superconductors Probed
by Resonant Elastic X-ray Scattering

Hsiao-Yu Huang (National Synchrotron Radiation Research Center)
17:15-17:35 Quantum critical scaling of charge order in La2-xSrxCuO4 revealed by high-resolution
RIXS

Mirian Garcia Fernandez (Diamond Light Source)
17:35:17:55 Low energy orbital excitations in A-site ordered SmBaMn O2

1

6

Thursday, August 3rd
Session Chair: Wei-Sheng Lee (SLAC National Accelerator Laboratory)
9:00-9:45
9:45-10:15

Mark P. M. Dean (Brookhaven National Laboratory)

Electronic structure, magnetic interactions, and charge order in low valence nickelates
probed by RIXS

Yao Wang (Clemson University)

Manipulation of Magnetic Excitations and Entanglement Enabled by trRIXS

Atsushi Hariki (Osaka Metropolitan University)
10:15-10:45 LDA+DMFT approach to resonant inelastic x-ray scattering in correlated materials
10:45-11:15 BreakSession Chair: Di-Jing Huang (National Synchrotron Radiation Research Center)
Hakuto Suzuki (Tohoku University)
11:15-11:45 Distinct spin and orbital dynamics in Sr RuO
2

4

Naoya Iwahara (Chiba University)
11:45-12:05 Vibronic excitations in resonant inelastic x-ray scattering spectra of spin-orbit Mott
insulators

Subhayan Roychoudhury (Lawrence Berkeley National Laboratory)

12:05-12:25 CleaRIXS: A fast and accurate first-principles method for the simulation and analysis ofresonant inelastic x-ray scattering

12:25-13:30 Lunch
13:30-14:30 Poster session
Session Chair: William Windsor (Fritz Haber Institute of the Max Planck Society)
Matteo Mitrano (Harvard University)
14:30-15:15 Towards a quantum x-ray spectroscopy of light-driven quantum materials
Giacomo Coslovich (SLAC National Accelerator Laboratory)
15:15-15:45 Ultrafast Resonant X-ray Scattering Reveals Light-enhanced Charge Density Wave
Coherence in a High-TC Superconductor

Nicolas Jaouen (Synchrotron SOLEIL)
15:45-16:15 Magnetic chirality in multilayers probed by Soft x-ray (coherent) scattering
16:15-16:45 BreakSession Chair: David Hawthorn (University of Waterloo)
Eugenio Paris (Paul Scherrer Institute)
16:45-17:15 Ultrafast Dynamics In Quantum Materials Using Time-resolved Resonant Inelastic X-ray
Scattering at SwissFEL Furka

Kenji Tsutsui (QST)

17:15-17:35 Theoretical study of magnetic excitations in a photoexcited Mott insulator on a squarelatticeVivek Kumar Bhartiya (Brookhaven National Laboratory)
17:35:17:55 Spectroscopic signature of 3D magnetism in a van der Waals ferromagnet Fe GeTe
5

19:00-21:00 Workshop Dinner22

Friday, August 4th
Session Chair: Ke-Jin Zhou (Diamond Light Source)
9:00-9:45
9:45-10:15

Jinghua Guo (Lawrence Berkeley National Laboratory)

Opportunities and challenges for the in-situ/operando soft X-ray spectroscopy in energy,
catalysis and chemical science

Jonathan Pelliciari (Brookhaven National Laboratory)

Resonant Inelastic X-Ray Scattering to study thin films of quantum materials

Wei-Sheng Lee (SLAC National Accelerator Laboratory)
10:15-10:45 RIXS Studies on Charge Order Phenomena in Cuprate and Nickelate Superconductors
10:45-11:15 BreakSession Chair: Johan Chang (University of Zurich)Thorsten Schmitt (Paul Scherrer Institut)
11:15-11:45 Spin-excitation anisotropy in the nematic state of detwinned FeS
Wenliang Zhang (Paul Scherrer Institut)
11:45-12:05 Observation of the Flat Magnon Band in the Ferromagnetic Topological Metal Fe3Sn2 by
Resonant Inelastic X-ray Scattering

Octave Duros (Sorbonne Université)
12:05-12:25 Expression and determination of the crystal electric field in the quantum spin-ice
candidate Yb2Ti2O7

12:25-13:50 Lunch
Session Chair: Hakuto Suzuki (Tohoku University)
Yi Tseng (Massachusetts Institute of Technology)
13:50-14:10 Exciton delocalization mediated by charge-transfer dynamics in van der Waals
semiconductors

Yuan Wei (Paul Scherrer Institut)

14:10-14:30 Spin-orbital excitations encoding the magnetic phase transition in the van der Waals
antiferromagnet FePS3

15:00-17:00 NanoTerasu Tour

3

Oral Presentation
Abstracts4

Spin and charge excitations in quantum materials probed by RIXS
Ke-Jin ZhouaaDiamond Light Source, Harwell Campus, Didcot, OX11 0DE, United Kingdom
Author Email: kejin.zhou@diamond.ac.uk

Resonant inelastic X-ray scattering (RIXS) is a photon-in photon-out spectroscopic technique capableof probing collective excitations or ordered states, such as magnons, orbitons, plasmons, phonons,
charge-density waves (CDW) in the energy-momentum space. Owing to its high cross-section andfocused X-ray beam, RIXS is advantageous in measuring micron-size samples and nanometer-thickfilms. Over the last decade, RIXS has flourished because of an order of magnitude increase in its energy
resolving power.
In the first part of my talk, I will present the results of spin excitations in a prototypical Haldane spin
chain material Y2BaNiO5 [1] and a ferromagnetic Kagome semimetal Co3Sn2S2 [2]. The studies establishthat RIXS is capable of probing more complex spin excitations beyond simple dipolar spin wave. In thesecond part of my talk, I will present some of recent studies on unconventional cuprate and infinitelayer nickelate superconductors. In single-layer bismuth-based cuprates, we found anisotropic CDW
peaks with elliptical shapes which is interpreted as evidence of unidirectional charge stripes hosted bymutually 90°-rotated anisotropic domains consistent with lanthanum- and yttrium- based cuprates [3].
For the newly discovered infinite-layer nickelates, plenty of spectroscopic results evidence that they
resemble cuprates in some respects but also possess its distinct electronic structure. The dispersive spin
excitations comparable to that in cuprates validate the existence of strong electron Coulomb interactions
in particular the proximity between the strong antiferromagnetic correlations and superconductivity [4].
Besides spin excitations, CDW was discovered in thin films of non-superconducting NdNiO2 [5-7]. This
CDW exists in Ni and Nd orbitals demonstrating a multi-orbital character distinct to cuprates [5]. Most
recently, abundant H is discovered in Nd0.8Sr0.2NiO2 where superconducting dome appears in a narrow
H doping window [8]. The results highlight the critical role of H for superconductivity in epitaxial
infinite-layer nickelates.
References[1] A. Nag, A. Nocera, S. Agrestini et al., Quadrupolar magnetic excitations in an isotropic spin-1 antiferromagnet.
Nat. Commun. 13, 2327 (2022).
[2] A. Nag, Y. Peng, J. Li et al., Correlation driven near-flat band Stoner excitations in a Kagome magnet. Nat.
Commun. 13, 7317 (2022).
[3] J. Choi, J. Li, A. Nag et al., Stripe symmetry of short-range Charge density waves in cuprate superconductors.
arXiv: 2301.07637.
[4] H. Lu, M. Rossi, A. Nag et al., Magnetic excitations in infinite-layer nickelates. Science 373, 213 (2021).
[5] C. C. Tam, J. Choi, X. Ding et al., Charge density waves in infinite-layer NdNiO2 nickelates. Nature Materials
21, 1116 (2022).
[6] M. Rossi, M. Osada, J. Choi et al., A broken translational symmetry state in an infinite-layer nickelate. Nature
Physics 18, 869 (2022).
[7] G. Krieger, L. Martinelli, S. Zeng et al., Charge and spin order dichotomy in NdNiO2 driven by the capping
layer. Phys. Rev. Lett. 129, 027002 (2022).
[8] X. Ding, C. C. Tam, X. Sui et al., Critical role of hydrogen for superconductivity in nickelates. Nature 615, 50(2023).

5

Magnon-magnon Interac�ons in So� Mot Insulators
Johan Chang1*, Qisi Wang2, Izabella Bialo1, Leonardo Martinelli1
University of Zurich, Switzerland
City University of Hong Kong, Hong Kong (SAR of China)
1

2

In this talk, recent RIXS results on Mot insula�ng cuprate compounds will bepresented. Analysis of magnon dispersions and magnon-magnon interac�ons will be
the focus. We will discuss higher order magne�c exchange interac�ons and theirrenormalisa�ons factors along with their implica�on for superconduc�vity in doped
compounds.

6

Charge order and its dynamics in overdoped Cuprates
Yingying Peng aaInternational Center for Quantum Materials, School of Physics, Peking University, China
Email: yingying.peng@pku.edu.cn

Charge orders (CO) are often considered a significant rival of high-temperature superconductivity inunderdoped cuprates [1]. In contrast, overdoped cuprates have traditionally been viewed as conventional
Fermi liquids without collective electronic order. However, our discovery of a reentrant CO in heavily
overdoped Bi2201 beyond the pseudogap phase challenges this assumption [2]. Despite this, there is noconsensus on whether CO is ubiquitous in heavily overdoped cuprates. Determining the extent of CO
across different doping and temperature ranges can help disentangle the relationship between
superconductivity, pseudogap, and CO phases, which is critical to understanding high-temperature
superconductivity. Using Cu L3 edge and O K edge resonant x-ray scattering, we have revealed thepresence of CO in overdoped La2-xSrxCuO4 (0.35  x 0.6) beyond the superconducting dome. We
observed similar in-plane momentum and polarization dependence and dispersive excitations as the COof underdoped cuprates, but its maximum intensity differed along the c-direction and persisted up to 300
K. The Fermi surface instability cannot explain this CO and its origin remains to be understood. Our
results suggest that CO is prevalent in the overdoped metallic regime, requiring a reassessment of the
traditional understanding of overdoped cuprates as weakly correlated Fermi liquids.
In our recent study on heavily overdoped Bi2201, we also used time-resolved resonant X-ray scattering
to examine CO dynamics [4,5]. We found that the charge order dynamics were distinct from thoseobserved in underdoped cuprates when using 800 nm and 400 nm laser pumps, suggesting that theorigins of CO in underdoped and overdoped cuprates may differ.
References[1] Ghiringhelli et al., Science 337, 821-825 (2012).
[2] Peng et al., Nat. Mater. 17, 697 (2018).
[3] Li et al., arXiv:2208.08634 (2022).
[4] Mitrano et al., Sci. Adv. 5: eaax3346 (2019).
[5] Wandel et al., Science 376, 860–864 (2022).

7

Excitonic excitations of cuprate superconductors probed withhigh-resolution RIXS
Di-Jing HuangaaNational Synchrotron Radiation Research Center, Hsinchu, Taiwan
Author Email: djhuang@nsrrc.org.tw

Recent advancements in synchrotron radiation instrumentation have enabled high-resolution
resonant inelastic X-ray scattering (RIXS) to become a powerful technique for probing elementary
excitations with momentum resolution and providing direct information about the dynamics arisingfrom fluctuations of spin, charge, and orbital degrees of freedom. This talk will begin with a review of
the advances in high-resolution RIXS instrumentation [1], followed by discussions of recent examples
of RIXS studies on cuprate superconductors [2, 3].
Electron quasiparticles play a crucial role in simplifying the description of many-body physics
in solids with surprising success. However, conventional Landau’s Fermi-liquid and quasiparticle
theories for high-temperature superconducting cuprates have received skepticism from various angles.
Whether the framework of electron fractionalization captures the essential physics of the pseudogap
and superconducting phases of cuprates is still an open issue. We will show that excitonic excitation of
optimally doped Bi2Sr2CaCu2O8+δ with energy far above the superconducting-gap energy scale, about
1 eV or higher, is unusually enhanced by the onset of superconductivity. Our findings prove theinvolvement of such high-energy excitons in superconductivity. Therefore, the observed enhancementin the spectral weight of excitons imposes a crucial constraint on theories for the pseudogap andsuperconducting mechanisms.
References[1] A. Singh et al., J. Synchrotron Radiat. 28, 977 (2021).
[2] H. Y. Huang et al., Phys. Rev. X 11, 04138 (2021).
[3] A. Singh, Nat. Commun. 13, 7906 (2022).

8

Plasmon excitations and plasmarons in cuprate superconductors
Hiroyuki Yamasea, Matias Bejasb, and Andres GrecobaResearch Center of Materials Nanoarchitectonics (MANA),

National Institute for Materials Science (NIMS), Tsukuba 305-0047, Japanb

Facultad de Ciencias Exactas, Ingenieria y Agrimensura andInstituto de Fisica Rosario (UNR-CONICET), Avenida Pellegrini 250, 2000 Rosario, Argentina
Email: yamase.hiroyuki@nims.go.jp
Charge fluctuations in cuprates may be categorized into two: i) the charge ordering tendency aroundthe momentum q≒(0.5p, 0) and (0.6p, 0) in electron- and hole-doped cases, respectively, and ii) the Vshaped dispersion around the Brillouin zone center in both electron- and hole-doped cases. The former
feature was interpreted as a d-wave bond-charge ordering tendency in electron-doped cuprates, but theorigin is still controversial in hole-doped cuprates. The latter feature was discussed controversially atthe early stage. The characteristic in-plane and out-of-plane momentum dependences and theobservation of a charge gap at the zone center indicated consistently the acoustic-like plasmons specificto layered materials. In particular, a large-N theory of the layered t-J model with the long-range Coulombinteraction can explain the experimental data nearly quantitatively.
In this talk, we first present what kind of charge excitation spectra are predicted in the large-N theoryof the t-J model—bond-charge excitations, acoustic-like plasmons, optical plasmons, and particle-holeexcitations in momentum-energy space, and then clarify how well the acoustic-like plasmons explain
the recent resonant inelastic x-ray scattering (RIXS) data [1]. The theory also explains consistently the
optical plasmon observed by electron energy-loss spectroscopy (EELS) [2]. We next study how thosecharge fluctuations renormalize the one-particle electron property by computing the electron self-energy[3]. In contrast to an electron-phonon interaction and a coupling to magnetic fluctuations, charge
fluctuations do not yield a kink in the electron dispersion. Instead, they yield the uniform suppressionof the spectral weight on the entire Fermi surface and the quasi-particle weight is reduced down to 1030 %, depending on parameters. The rest of the spectral weight is transferred to high energy regions,but in a very asymmetric way with respect to zero energy. This asymmetry comes from the strong
correlation effect, not from the underlying band structure. In particular, an incoherent band is generated
near the energy controlled by the optical plasmon energy. This incoherent band is the so-called replicaband dubbed as plasmarons [4]. Recalling that plasmarons were discussed in weakly correlated systems
such as graphene, two-dimensional electron systems, and SrIrO3 films, it is intriguing that the same
plasmarons are predicted in cuprates, too, where the strong correlation effect is definitely important. The
predicted dispersion may be tested by collaborating with a community of angle-resolved photoemission
spectroscopy.
References[1] A. Greco, H. Yamase, and M. Bejas, Commun. Phys. 2, 3 (2019); A. Nag et al., Phys. Rev. Lett. 125,
257002 (2020); A. Greco, H. Yamase, and M. Bejas, Phys. Rev. B 102, 024509 (2020); H. Yamase, J.
Phys. Soc. Jpn. 90, 111011 (2021); M. Hepting et al., Phys. Rev. Lett. 129, 047001 (2022).
[2] A. Greco, H. Yamase, and M. Bejas, Phys. Rev. B 94, 075139 (2016).
[3] H. Yamase, M. Bejas, and A. Greco, Phys. Rev. B 104, 045141 (2021).
[4] H. Yamase, M. Bejas, and A. Greco, arXiv: 2208.11421.

9

Resonant Scattering to Study Ultrafast Dynamics of Spins and Electrons
and the Relation to the Dynamics of the LatticeUrs Staub
Swiss Light Source, Forschungsstrasse 111, Paul Scherrer Institute, 5232 Villigen, Switzerland
Urs.staub@psi.ch
In my presentation, I will concentrate on investigations using transient resonant x-ray diffraction to
study ultrafast dynamics of electronic and magnetic properties of materials. I will first discuss the caseof ultrafast suppression of antiferromagnetic order in insulators, exemplified on different multiferroic
materials such as CuO [1], TbMnO3 [2,3] and hexaferrites [4]. These soft x-ray diffraction studies
shown how a near infrared laser pulse demagnetize magnetic sublattices of the antiferromagnet. The
observed timescales for the suppression of the antiferromagnetic order parameter is strongly material
dependent and not yet fully understood. In a second step, I will show how THz pulses, short pulses ofelectric fields, can interact with the magnetic order leading to coherent (electro) magnon excitations.
[5] This type of study is extended with very recent results from the free electron laser SwissFEL. A
hard x-ray diffraction study using the BERNINA endstation allowed a direct visualization of thephononic contribution of an electromagnon. A resonant soft x-ray magnetic diffraction study from thebrand-new FURKA endsation addressed the corresponding spin motion in real time. [6] The observed
phase shift between the coherent resonant excitation of the lattice (phonon) and the spins (magnon)show that the E-field of the excitation drives the lattice first, which in turn changes the magnetic
Hamiltonian that creates an effective magnetic field, which in turn drives the spins. In the last example,
ultrafast hard x-ray resonant diffraction is used to study the response to a coherent excitation of a quasitwo-level orbital system in Tb2Ti2O7. The excitation creates a quantum coherence entanglement of thestates, which is observed through an induced spin rotation.
[1] S. L. Johnson et al., Phys. Rev. Lett. 108, 037203 (2012).
[2] J. A. Johnson et al., Phys. Rev. B, 92, 184429 (2015).
[3] E. Abreu et al., Phys. Rev. B 106, 214312 (2022).
[4] H. Ueda et al., Phys. Rev. Research 4, 023007 (2022).
[5] T. Kubacka et al., Science 343,1333 (2014).
[6] H. Ueda et al., arXiv:2306.02676

10

Circularly polarized resonant x-ray diffraction of multiferroic CuO
T. Kimuraa, R. Misawab, K. Arakawab, H. Nakajimac, S. Moric, H. Uedad, Y. TanakaeaDepartment of Applied Physics, University of Tokyo, bDepartment of Advanced Materials Science,
University of Tokyo, cOsaka Metropolitan University, dSwissFEL, Paul Scherrer Institute,e
RIKEN SPring-8 Center
Author Email: tkimura@ap.t.u-tokyo.ac.jp

CuO has attracted considerable attention since its multiferroic nature was discovered in 2008 [1]. This
compound exhibits successive antiferromagnetic (AFM) phase transitions at TN1 = 213 K and TN2 = 230
K. At temperature (T) below TN1, CuO shows a collinear AFM order with the commensurate propagation
vector qCM (0.5, 0, -0.5). At TN1 ≤ T ≤ TN2, the Cu moments show a spiral spin order with theincommensurate propagation vector qICM (0.506, 0, -0.483). This spiral spin arrangement breaks
inversion symmetry and induces improper ferroelectricity in which spin helicity is a primary orderparameter [1]. Apart from the multiferroic nature in the ICM phase, the CM phase of CuO has been
proposed to have an orbital current that is characterized by a time-odd polar vector corresponding to ananapole or toroidal moment [2].
In this study, we investigate resonant x-ray diffraction of CuO using circularly polarized x rays [3].
Circular dichroism on magnetic Bragg reflections in two distinct AFM phases (ICM spiral and CM
collinear AFM phases) was observed at around the Cu L3 edge. In the ICM phase where spin-spiralinduced ferroelectricity develops, it is reasonably considered that circular dichroism and its sign are
ascribed to the spiral magnetic order and the sign of spin helicity (i.e., ferroelectricity), respectively. In
the CM phase, weaker but substantial circular dichroic signals are observed. Measurements of spatial
distributions of the circular dichroism revealed the presence of magnetic domains with rectilinear
domain boundaries in both phases. It is found that the domain structures in the two phases resemble eachother, suggesting some correlation between the ICM and the CM phases. Furthermore, a comparison of
the magnetic domain structures with dark-field images obtained by electron diffraction measurements
revealed that the domain boundaries observed in the two phases were strongly influenced by
crystallographic twin structures. This study clarified the correlation between the crystallographic defectstructure and the magnetic domain structures in antiferromagnetic CuO.
References[1] T. Kimura, Y. Sekio, H. Nakamura, T. Siegrist, and A. P. Ramirez, Nat. Mater. 7, 291 (2008).
[2] V. Scagnoli, U. Staub, Y. Bodenthin, R. A. de Souza, M. GarcíaFernández, M. Garganourakis, A. T.
Boothroyd, D. Prabhakaran, and S. W. Lovesey, Science 332, 696 (2011).
[3] R. Misawa, K. Arakawa, H. Ueda, H. Nakajima, S. Mori, Y. Tanaka, and T. Kimura, Phys. Rev. B 106,
104401 (2022).

11

Towards control of ultrafast spin dynamics in 4f antiferromagnets
Y. W. Windsor1, S-E. Lee1, D. Zahn1, V. Borisov2, D. Thonig3, K. Kliemt4, A. Ernst5,6, C.
Schüßler-Langeheine7, N. Pontius7, U. Staub8, C. Krellner4, D. V. Vyalikh9,10, O. Eriksson2, L.
Rettig1
1

Fritz Haber Institute of the Max Planck Society, Berlin, Germany

4
5
6
7

2

Uppsala University, Sweden

3Örebro University, Sweden

Goethe-Universität Frankfurt, Germany

Johannes Kepler University, Linz, Austria

Max-Planck-Institut für Mikrostrukturphysik, Halle (Saale), Germany

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany
8
910Paul Scherrer Institut, Switzerland

Donostia International Physics Center, Spain

IKERBASQUE, Basque Foundation for Science, Spain
Author Email: windsor@tu-berlin.de

Ultrafast manipulation of magnetism bears great potential for future information technologies. Whiledemagnetization in ferromagnets is governed by the dissipation of angular momentum, materials withmultiple spin sublattices, for example antiferromagnets, can allow direct angular momentum transfer
between opposing spins, promising faster functionality. Furthermore, a central prospect of
antiferromagnetic spintronics is to exploit magnetic properties that are unavailable with ferromagnets.
However, this poses the challenge of accessing such properties for readout and control.
Here I will present a series of ultrafast (“pump-probe”) resonant soft X-ray diffraction studies that wehave conducted, in which we address these prospects in Lanthanide-based antiferromagnets. 4f
magnetism is usually mediated indirectly through the conduction electrons, in an effect known as the
RKKY interaction. We have studied how tuning RKKY affects ultrafast magnetization dynamics in 4f
antiferromagnets. This was done both by systematically varying the 4f occupation [1] and by altering
the conduction electrons (thereby altering RKKY’s magnitude). We
find that the rate of direct angular momentum transfer between
opposing moments is directly determined by this coupling. We havefurther studied light-induced manipulation of the transient ground state
in one such material [2]. We trigger a coherent rotation of the entire
long-range antiferromagnetic spin arrangement about a crystalline axis,
thereby demonstrating deterministic control of this rotation. Our
observations allow for a quantitative description of the transientmagnetic anisotropy potential of the Lanthanide ions.
References[1] Windsor et al., Nature Materials 21, 514–517 (2022)[2] Windsor et al., Communications Physics 3, 139 (2020)12Orbital/Nematic and Charge Density Wave Orders in Cuprate
Superconductors Probed by Resonant Elastic X-ray Scattering
David HawthornaaDepartment of Physics and Astronomy, University of Waterloo, Waterloo, N2L 3G1, Canada.
Author Email: dhawthorn@uwaterloo.ca

Charge density wave (CDW) order has been established as a generic feature of the cuprate phase diagram,competing and co-existing with superconductivity. While most commonly characterized by a Bragg
�⃗CDW indictive of a translational symmetry breaking order parameter, CDW order can also
peak at finite 𝑄𝑄
couple to orbital degrees of freedom, evident by Qx = Qy = 0 orbital/nematic order. How these orders
manifest and couple to each other can depend on the structure of the material and hole doping, and may
play an important role in how CDW order varies amongst the different families of cuprates. In this talk,we explore the relationship between structural distortions, (Qx = Qy = 0) nematic/orbital order and CDW
using equilibrium and pump-probe resonant x-ray scattering measurements in the(La,M)2CuO4 familyof cuprate superconductors. These measurements demonstrate orbital/nematic order to be coupled to but
distinct from CDW order. We will also show nematic order to be associated with the pseudogap phaseof the cuprates, with signatures of nematic order present within the pseudogap phase, but vanishing
above the pseudogap critical doping, p*, and temperature, T* in overdoped cuprates.
References[1] Martin Bluschke, Naman K Gupta, Hoyoung Jang, Ali A Husain, Byungjune Lee, MengXing Na, Brandon
Dos Remedios, Sang-Youn Park, Minseok Kim, Dogeun Jang, Hyeongi Choi, Ronny Sutarto, Alexander H Reid,
Georgi L Dakovski, Giacomo Coslovich, Quynh L Nguyen, Nicolas G Burdet, Ming-Fu Lin, Alexandre
Revcolevschi, Jae-Hoon Park, Jochen Geck, Joshua J Turner, Andrea Damascelli, David G Hawthorn.
Nematicity dynamics in the charge-density-wave phase of a cuprate superconductor. arXiv/2209.11528[2] Naman K. Gupta, C. McMahon, R. Sutarto, T. Shi, R. Gong, Haofei I. Wei, K. M. Shen, F. He, Q. Ma, M.
Dragomir, B. D. Gaulin, D. G. Hawthorn. Vanishing nematic order beyond the pseudogap phase in overdoped
cuprate superconductors. Proceedings of the National Academy of Sciences 118 (34), e2106881118 (2021).
[3] A. J. Achkar, M. Zwiebler, Christopher McMahon, F. He, R. Sutarto, Isaiah Djianto, Zhihao Hao, Michel J.
P. Gingras, M. Hücker, G. D. Gu, A. Revcolevschi, H. Zhang, Y.-J. Kim, J. Geck and D. G. Hawthorn.
Nematicity in stripe-ordered cuprates probed via resonant x-ray scattering. Science 351, 576 (2016).

13

Quantum critical scaling of charge order in La2−xSrxCuO4
revealed by high-resolution RIXS
Hsiao-Yu Huanga, Amol Singha, Chung-Yu Moub, Jun Okamotoa, Seiki Komiyac,
Atsushi Fujimorid,e, Chien-Te Chena, Di-Jing Huanga,eaNational Synchrotron Radiation Research Center, bNational Tsing Hua University Taiwan(Center for Quantum Technology and Department of Physics), cCentral Research Institute ofElectric Power Industry, dUniversity of Tokyo (Department of Physics), eNational Tsing Hua
University Taiwan (Department of Physics)
Author Email: huang.hy@nsrrc.org.tw
The pseudogap (PG) and strange-metal (SM) phases observed in cuprates above the superconductivity
transition temperature are enigmatic. Quantum phase transitions, which are driven by nonthermal
fluctuations at absolute zero temperature, play a crucial role in shaping the phase diagram of hightemperature cuprate superconductors. Understanding the PG and the SM phases might hinge on theinfluence of quantum criticality at finite temperatures. Recently, quantum fluctuations of charge-density
waves (CDW) were observed in different families of cuprates [1-4]. In this study, we investigated thehigh-resolution resonant inelastic x-ray scattering (RIXS) of La2−xSrxCuO4 to unravel the quantum
fluctuations of CDW in different doping. Our findings provide the spectroscopic signature of quantum
critical scaling in cuprates, in which the PG and SM phases correspond to the renormalized classical andquantum critical scaling regimes, respectively. In addition, the characteristic energy Δ of the CDW
fluctuations at zero temperature determines the crossover temperature T* between the PG and the SMphases, i.e., T* ∼ Δ.
References[1] R. Arpaia et al., Science 365, 906 (2019).
[2] W. S. Lee et al., Nat. Phys. 17, 53 (2021).
[3] H. Y. Huang et al., Phys. Rev. X 11, 041038 (2021).
[4] G. Seibold et al., Commun. Phys. 4, 7 (2021).

14

Low energy orbital excitations in A-site ordered SmBaMn2O6.
Mirian Garcia FernandezaDiamond Light Source

Harwell Campus, Didcot, OX11 0DE, United Kingdom
Author Email: mirian.garcia@diamond.ac.uk
In the last few decades plenty of experimental and theoretical research efforts have been devoted toperovskite manganites with chemical formula R1-x 3+Ax2+MnO3 (R3+= rare earth ions, A2+=alkaline-earthions). These materials show a rich variety of fascinating electromagnetic properties, such as the colossal
magnetoresistance (CMR), charge and orbital ordering (COO), and metal-insulator transition. Recently
it has been shown that an additional control parameter besides doping content and ionic radii of the Asite ions is the A-site randomness. Hence LBaMn2O6 compounds with L = Sm, Eu, Gd, Tb, Dy, Ho andY have attracted a lot of attention.
We present the combination of soft x-ray RIXS and REXS measurements performed in A-site ordered
SmBaMn2O6. The elimination of the A-site randomness in these manganites allows for the orbital order
to be long ranged. Evidence of this is that even on polycrystalline samples of this material, orbital order
was observed by soft x-ray REXS1-3. High quality single crystals of this compound have only recently
become available and have allowed for this RIXS study. This compound undergoes a two-step COO
transition at temperatures Tco1 and Tco2 as the temperature decreases. In the second temperature transition
Tco2, a disappearance of the four-fold periodicity along the c-axis has been suggested to be caused by
the change on the stacking manner of the COO
phases, however the models have not been uniquelydetermined due to lack of definitive experimental
evidence1,4-8. In a single crystal of SmBaMn2O6 wemeasured the [1/4 1/4 0] orbital order reflection1-3.
The energy dependence of this reflection shown in
the insert of Figure 1 demonstrates its resonant
behaviour. We collected RIXS data shown in Figure
1 at the OO geometry. Low energy excitations
could be identified which may be compatible with
the Jahn-Teller stretching and the breathing modes9.
The temperature dependence of the RIXS spectra
illustrate the evolution of low energy excitations
Figure 1 RIXS spectra measured at the Mn L3 edge. The
acrossthe phase diagram of the system. RIXS
spectrum has been fitted with 4 gaussians. In the insert ismeasurements
collected as a function of energy andshown in blue the energy dependence of the orbital order[1/4 1/4 0] reflection and in red the XAS, both measured in fixed q further demonstrate the dependence of thethe vicinity of the Mn.
low energy excitations with the OO signal. Owing
to the strong electron-phonon coupling in strongly correlated electron systems, it is possible to obtain alot of information about the electronic properties and the phonon behaviour across the orbital ordering
phase.
This is the first combined study of RIXS and REXS in a 3d half doped manganite with orbital ordering.
References[1]M. García-Fernández, et al. Phys. Rev. B 77,
060402(R) (2008)[2]M. García-Fernández, et al. Phys. Rev. Lett. 103,
097205 (2009)[3]M. García-Fernández, et al. Phys. Rev. B 82,
235108 (2010)[4] J.M. Chen et al. Phys. Rev. B, 82,094442(2010)[5] X. Liu et al. Phys. Rev. B, 87, 201103(R)(2013)[6] Kenji Ishii et al. J. Phys Soc Jap 82 (2013)
021015[7]T. Nakajima et J. Phys. Soc. Jpn, 73(2004)[8]M. Uchida et al. J. Phys. Soc. Jpn, 71(2002)
2605[9] Rea Divina Mero et al. Nature Scientific Report(2019) 9:1816

15

Electronic structure, magnetic interactions, and charge order in low
valence nickelates probed by RIXSMark P. M. Deana and Yao Shenaa

Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory,
Upton, New York 11973, USA
Author Email: mdean@bnl.gov

After a 30-year quest, researchers recently succeeded in realizing superconductivity in low valencenickelates [1]. This ignited a vigorous debate regarding the essential electronic properties of thesematerials and their similarity to cuprates. Some important questions include: Do these materials haveappreciable oxygen charge-transfer character and superexchange akin to the cuprates or are they in a
distinct Mott-Hubbard regime where oxygen plays a minimal role and superexchange is negligible?
Given that cuprates have a propensity to host proximate competing phases such as charge and spin order,
one might ask whether the nickelate’s phase diagrams also host competing orders and to what extent
they are similar to those in cuprates? In this talk, I will give a perspective of where we are with thesequestions, including our studies of the trilayer low valance nickelate La 4Ni3O8 [2-5].
References[1] Danfeng Li, Kyuho Lee, Bai Yang Wang, Motoki Osada, Samuel Crossley, Hye Ryoung Lee, Yi
Cui, Yasuyuki Hikita & Harold Y. Hwang, Nature 572, 624–627 (2019)[2] J. Q. Lin, P. Villar Arribi, G. Fabbris, A. S. Botana, D. Meyers, H. Miao, Y. Shen, D. G. Mazzone,
J. Feng, S. G. Chiuzbaian, A. Nag, A. C. Walters, M. Garcia-Fernandez, Ke-Jin Zhou, J. Pelliciari, I.
Jarrige, J. W. Freeland, Junjie Zhang, J. F. Mitchell, V. Bisogni, X. Liu, M. R. Norman, and M. P. M.
Dean, Phys. Rev. Lett. 126, 087001 (2021)[3] Y. Shen, J. Sears, G. Fabbris, J. Li, J. Pelliciari, I. Jarrige, Xi He, I. Bozovic, M. Mitrano, Junjie
Zhang, J. F. Mitchell, A. S. Botana, V. Bisogni, M. R. Norman, S. Johnston, and M. P. M. Dean, Phys.
Rev. X 12, 011055 (2022)[4] Y. Shen, J. Sears, G. Fabbris, J. Li, J. Pelliciari, M. Mitrano, W. He, Junjie Zhang, J. F. Mitchell, V.
Bisogni, M. R. Norman, S. Johnston, and M. P. M. Dean, Phys. Rev. X 13, 011021 (2023)[5] G. Fabbris, D. Meyers, Y. Shen, V. Bisogni, J. Zhang, J.F. Mitchell, M.R. Norman, S. Johnston, J.
Feng, G.S. Chiuzbaian, A. Nicolaou, N. Jaouen, and M. P. M. Dean, Scientific Data 10, 174(2023)

16

Manipulation of Magnetic Excitations and Entanglement Enabled by
trRIXS1

Yao Wang
Department of Physics and Astronomy, Clemson University

The rapidly evolving quantum science calls for precise and predictive control of collective electronic properties
beyond the classical realm. Among various control knobs, an ultrafast laser pump is a promising approach due
to its rich degrees of freedom. Together with the laser's capability of influencing electronic structure comes thenecessity to track the instantaneous status of a time-dependent nonequilibrium material. In this talk, I will
discuss the application of time-resolved resonant inelastic x-ray scattering (trRIXS) in magnetic materials. By
comparing the trRIXS for antiferromagnetic materials, we find that the instantaneous paramagnon excitations
can be manipulated by pulsed laser in a predictive manner, following the Floquet theory in the center of thepulse. Such a Floquet engineering works only at doped Mott insulators without long-range order, while thetrRIXS study of an undoped Mott insulator violates the Floquet approximation. Leveraging the light-engineered
magnetic excitations, we further study the nonequilibrium dynamics of a 1D cuprate chain. Through a selfconsistent iteration, trRIXS can probe the transient entanglement of wavefunctions in nonequilibrium materials
via the quantum Fisher information. Via this approach, we reveal the possibility of enhancing entanglement ina cuprate chain using an ultrafast laser pulse.

17

LDA+DMFT approach to resonant inelastic x-ray scatteringin correlated materials
Atsushi Harikia and Jan KunešbaDepartment of Physics and Electronics, Osaka Metropolitan University,1-1 Gakuen-cho, Nakaku,
Sakai, Osaka 599-8531, Japanb

Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria
hariki@omu.ac.jp

We present an ab-initio method for simulating resonant inelastic x-ray scattering (RIXS) spectra instrongly correlated 3d transition-metal and 4f rare-earth materials. The method builds on a combinationof density functional theory (DFT) and dynamical mean-field theory (DMFT). This method includes
both local excitations (e.g. atomic multiplet excitation) and continuum of unbound electron-hole pairs
as well as charge-transfer excitations in a unified way and material specific manner [1,2]. The heart ofthis computational method is a configuration-interaction impurity solver that allows to compute RIXS
intensities efficiently from a multi-orbital Anderson impurity model with the DMFT hybridization
densities and core orbitals including full core-valence multiplet interaction explicitly in the intermediate
states of RIXS.
In this talk, we present recent applications of the LDA+DMFT method for correlated materials: Ledge RIXS in NiO (canonical Mott insulator), LuNiO3 (site-selective Mott insulator) [3], infinite-layer
nickelate [4], and M-edge RIXS for CePd3 (prototype 4f Kondo lattice system) [5]. With these examples,
we demonstrate the capability of RIXS to advanced understanding of the dynamics and interplay of thespin, orbital and charge degrees of freedom in correlated materials.
References[1] A. Hariki et al., Phys. Rev. Lett. 121. 126403 (2018).
[2] A. Hariki et al., Phys. Rev. B 101, 115130 (2020).
[3] M. Winder et al., 102, 085144 (2020).
[4] K. Higashi et al., Phys. Rev. X 11, 041009 (2021).
[5] M. C. Rahn et al., Nat. Commun. 13, 6129 (2022).

18

Distinct spin and orbital dynamics in Sr2RuO4
H. Suzukia,b, L. Wanga, J. Bertinshawa, H. U. R. Strandc, S. Kaesera, M. Krautlohera,
Z. Yanga, N. Wentzelld, O. Parcolletd, F. Jerzembecke, N. Kikugawae, A. P. Mackenziee,
A. Georgesd,f, P. Hansmanng, H. Gretarssona.h, and B. KeimeraadMax-Planck-Institut f ü r Festk ö rperforschung, bTohoku University ,cOrebro University,
Flatiron Institute, eMax Planck Institute for Chemical Physics of Solids, fEcole Polytechnique,gFriedrich-Alexander-University of Erlangen-Nurnberg, hDESY
Author Email: hakuto.suzuki@tohoku.ac.jp

The unconventional superconductor Sr2RuO4 has long served as a benchmark for theories ofcorrelated electron materials. Recent precision experiments in the superconducting state havecast doubt on the previously advocated spin-triplet pairing scenario, thus revitalizing the orderparameter debate and the search for an in-depth understanding of the Fermi-liquid normal stateand collective bosonic fluctuations relevant to superconductivity. However, the lack of
information on high-energy magnetic excitations from neutron scattering experiments
precludes the understanding of the global picture of the spin fluctuations and the role of orbital
degrees of freedom. This hinders an experimental test of different theoretical frameworks to the
dynamical properties of Sr2RuO4.
To collect comprehensive information on the spin and orbital fluctuations of Sr2RuO4, we have
performed resonant inelastic x-ray scattering (RIXS) at the Ru L3 edge (2838 eV) [1]. The
experiment was performed using the newly-developed IRIXS spectrometer [2] at the P01
Beamline of PETRA III, DESY.
We have observed multiple branches of dispersive spin and orbital excitations from the Fermi
liquid state of Sr2RuO4, including the well-known incommensurate spin fluctuations.
Theoretical spin and orbital dynamical response functions calculated within the dynamical
mean-field theory excellently capture the key features of the RIXS spectra, whereas
perturbative random phase approximation fails to reproduce the experimental observations. By
establishing the properties of key collective modes, our results provide a solid baseline for the
future identification of the nature and symmetry of superconducting order in this material.
References[1] H. Suzuki et al., arXiv:2212.00245[2] H. Gretarsson et al., J. Synchrotron Rad. 27, 538 (2020)19

Vibronic excitations in resonant inelastic x-ray scattering spectra ofspin-orbit Mott insulators
Naoya Iwaharaa, Shouta Shikanob, Wataru Furukawabab

Graduate School of Engineering, Chiba University, Japan

Department of Materials Science, Faculty of Engineering, Chiba University, Japan.
Email: naoya.iwahara@gmail.com

Spin-orbit Mott insulators with heavy 4d/5d transition metal ions attract significant increasing attention
because they could exhibit novel phases such as Kitaev spin liquie phase, excitonic magnetic phase, andmultipolar phases [1]. To characterize the nature of the 4d/5d transition metal compounds, precise
knowledge of the elementary excitations is desired. To this end, resonant inelastic x-ray scattering(RIXS) has been an indispensable technique to probe complex elementary excitations. The local
quantum states of these compounds have been analyzed based on the interplay of ligand-field and spinorbit coupling. However, the conventional analyses of recent RIXS spectra of cubic double perovskites
fail to provide reasonable physical pictures. In the case of the RIXS spectra of K2RuCl6 (Figure), thespin-orbit based analysis suggested a large reduction of the spin-orbit coupling by 50 % compared withthe value extracted from magnetic susceptibility measurements of the same compound [2, 3]. In the caseof K2IrCl6, splitting of a peak in the RIXS spectra was interpreted as ligand-field splitting, which iscontradictory to the neutron diffraction data showing no symmetry lowering down to 0.3 K [4]. As an
origin of such puzzling situations, presence of dynamic Jahn-Teller (JT) effect in the excited states has
been mentioned, whereas the presence and its impact on the RIXS spectra are unknown.
In this presentation, we address two issues: (i) the presence of the dynamic JT effect in the cubic spinorbit Mott insulators, and (ii) the impact of the dynamic JT effect on the RIXS spectra. Taking 5d5 ion(Ir4+) as an example, we simulated the RIXS spectra of a single ion with dynamic JT effect in the excited
spin-orbit multiplet states [5]. The simulated RIXS spectra show a clear splitting of the RIXS spectra
due to vibronic excitations (Figure). Increasing temperature, we could also reproduce the temperature
evolution of the RIXS spectra of the Ir compound. Based on the first-principles calculations, we
confirmed the validity of the chosen interaction parameters for my simulations. Similarly, we could
explain the shape and temperature evolution of the RIXS spectra of Ru4+ (4d4) ion by fully considering
the dynamic JT effect [6]. Our work established the emergence and the fingerprints of the dynamic JT
effect in RIXS spectra of spin-orbit Mott insulators.

Figure. Left: K2MCl6 (M = Ru, Ir). Right: RIXS spectra of 5d5 ion including the vibronic excitations.
References[1] T. Takayama et al., J. Phys. Soc. Jpn. 90, 062001 (2021).
[2] H. Takahashi et al., Phys. Rev. Lett. 127, 227201 (2021).
[3] P. Vishnoi et al., Angew. Chem. Int. Ed. 60, 5184 (2021).
[4] D. Reig-i Plessi et al., Phys. Rev. Mater. 4, 124407 (2020).
[5] N. Iwahara and W. Furukawa, in preparation.
[6] N. Iwahara and S. Shikano, Phys. Rev. Research 5, 023051 (2023).

20

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Subhayan Roychoudhurya, David PrendergastaaLawrence Berkeley National Laboratory
Berkeley, California 94720
United States
Author Email: subhayan@lbl.gov

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

Towards a quantum x-ray spectroscopy of light-driven quantum materials
Matteo MitranoaaDepartment of Physics, Harvard University, USA
Author Email: mmitrano@g.harvard.edu

Optically excited quantum materials exhibit striking emergent phenomena ranging from light-controlled
magnetism and ferroelectricity to Floquet topological states and light-induced superconductivity.
Central to the appearance of these nonequilibrium phenomena is a variety of excitation mechanisms
involving intertwined electronic, structural, magnetic, and orbital degrees of freedom and theirinteraction with ultrafast laser fields. However, understanding how these ingredients determine thenonequilibrium behavior at the macroscale requires microscopic knowledge of many-body interactions
and wavefunctions of the excited state.
By using the light-induced renormalization of the effective electronic interactions as an example, I willshow how time-resolved x-ray absorption spectroscopy (trXAS) and resonant inelastic x-ray scattering(trRIXS) provide a unique view of the transient electronic structure of light-driven quantum materials[1]. Further, I will discuss how polarization-resolved trXAS and trRIXS are able to map the effective
interactions of two cuprate superconductors with distinct effective dimensionality [2,3]. I will thendiscuss constraints about structure of the driven state wavefunction and implications of our findings for-pairing and other driven, long-range-ordered phases.
In addition to these advances, I will introduce a novel approach aimed to witness entanglement in the
excited state [4,5]. The key idea is to extract quantum metrological operators, such as the quantum Fisher
information, together with operator-specific quantum bounds to determine the presence of multipartite
entanglement of the driven state wavefunction from the trRIXS signal. This approach, along with acomprehensive mapping of the excited state using trRIXS and trXAS, represents a significant step
towards a quantum x-ray spectroscopy of light-driven quantum materials, and will enable novel routes
to harness their unique functionalities.
References[1] M. Mitrano & Y. Wang, Commun. Phys. 3, 184 (2020).
[2] D. R. Baykusheva, et al., Phys. Rev. X 12, 011013 (2022).
[3] D. R. Baykusheva, et al., forthcoming (2023).
[4] D. R. Baykusheva, et al., Phys. Rev. Lett. 130, 106902 (2023).
[5] J. Hales, et al., Nat. Commun., in press (2023).

This study was supported by the DOE Office of Science under the Early Career Research Program
award No. DE-SC0022883. Use of the Linac Coherent Light Source (LCLS), SLAC National Accelerator
Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy
Sciences under Contract No. DE-AC02-76SF00515. Work at Brookhaven National Laboratory was
supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

22

Ultrafast Resonant X-ray Scattering Reveals Light-enhanced Charge
Density Wave Coherence in a High-TC Superconductor
G. CoslovichaaLinac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California
94720, USA
Author Email: gcoslovich@slac.stanford.edu

The use of ultrashort X-ray pulses offers new opportunities to study fundamental interactions inmaterials exhibiting unconventional quantum states, such as stripes, charge density waves and hightemperature superconductivity. To understand the microscopic interdependence between these orderparameters, a probe capable of discerning their interaction on its natural length and time scales isnecessary. In this talk, I will focus on recent ultrafast resonant soft x-ray scattering results tracking thetransient evolution of charge density wave correlations in the high-TC superconductor YBa2Cu3O6+x [1].
In this study, ultrashort infrared pulses produce a non-thermal quench of the superconducting state while
X-ray pulses detect the reaction of charge density waves. The response happens on a picosecond
timescale and is characterized by a large enhancement of spatial coherence of charge density waves,nearly doubling their correlation length, accompanied by a smaller increase of their amplitude. Suchbehavior can be reversed at higher fluences and at higher temperatures (above TC, 65 K) where thephoto-induced charge density wave melting process takes place instead.
This ultrafast snapshot directly reveals the coupling between superconductivity and charge density
waves on its natural timescale. It demonstrates that their competition manifests inhomogeneously at thenanoscale level, as disruption of spatial coherence, indicating the role of superconductivity in stabilizing
topological defects within charge density waves domains. The study highlights a path for enhancing
spatial coherence (order) by using light pulses by changing the balance between intertwined orders andit represents a unique opportunity for this growing technique in resonant X-ray scattering. In conclusion,
I will also discuss ongoing developments at the LCLS to further expand on these results and unlock
novel capabilities to control and observe quantum materials with light pulses.

Image credit: Greg Stewart, SLAC

References[1] S. Wandel, F.Boschini, E. H. da Silva Neto, L. Shen, M. X. Na, S. Zohar, Y. Wang, S. B. Welch, M. H.
Seaberg, J. D. Koralek, G. L. Dakovski, W. Hettel, M.-F. Lin, S. P. Moeller, W. F. Schlotter, A. H. Reid, M.
P. Minitti, T. Boyle, F. He, R. Sutarto, R. Liang, D. Bonn, W. Hardy, R. A. Kaindl, D. G. Hawthorn, J.-S.
Lee, A. F. Kemper, A. Damascelli, C. Giannetti, J.J. Turner, G. Coslovich, Science 376, 860 (2022).
* Use of the Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, is supported by the
U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DEAC02-76SF00515.

23

Magnetic chirality in multilayers probed by Soft x-ray (coherent) scattering
Nicolas JaouenaaSynchrotron SOLEIL, Saint-Aubin, 91192 Gif-sur-Yvette Cedex, France
Author Email: Nicolas.jaouen@synchrotron-soleil.fr

Many current forthcoming applications of magnetic materials involve heterostructures or alloys containing
magnetic and non-magnetic elements. X-ray Resonant (Coherent) Scattering is the technique of choice to probe
such phenomena thanks to its element-selectivity and spatial sensitivity.
In this presentation I will introduce the experimental set-up that we developed at SOLEIL and illustrate
their capabilities. SEXTANTS [1] is a beamline of the SOLEIL synchrotron, covering the 50-1700eV energy
range dedicated to soft x-ray scattering. The resolving power exceeds 10000 and maximum flux on the sample
ranges from 1×1014 (100 eV) to 2×1013 (1000 eV) ph./s/0.1% bw. The beamline main objective is theinvestigation of the electronic and magnetic properties of solids using three scattering techniques: resonant
inelastic x-ray scattering (RIXS), x-ray resonant magnetic scattering (XRMS) and coherent x-ray scattering(CXS), the last one including also imaging via Fourier transform holography (FTH) [2, 3].
In the second part, several recent results obtained at SEXTANTS beamline will be presented, and inparticular I will show that XRMS is the tool to study magnetic chirality in prototype Pt/Co multilayers in which
Dzyaloshinskii-Morya interaction (DMI) is induced by the inversion symmetry breaking at the interfaces [3] andhow it was possible to reveal the hybrid character of the magnetic structure in thick multilayer [4]. I will alsopresent how one can manipulate this magnetic chirality either statically using magnetic field or at the
femtosecond timescale using optical light [5].
In the last part I will present the latest development of resonant scattering and in particular how the useof the x-ray coherence already available at modern light source, and expected to increase by few orders ofmagnitude in the planned upgrade sources, allow nowadays to image the sample with a spatial resolution of few
tens of nanometers and a time resolution ranging from ns down to few ps timescale.
If your abstract contains figures and pictures, make sure they are included in the word document.
References[1] M. Sacchi et al., Journal of Physics: Conference Series 425 (2013) 072018[2] S. Eisebitt et al., Nature, 432, 885 (2004).
[3] H. Popescu et al., J. Synchr. Rad 26(1), 280-290 (2019)[3] J.Y. Chauleau et al., Phys. Rev. Lett. 120, 037202 (2018).
[4] W. Legrand et al, Sci. Adv. 2018; 4:eaat0415 (2018).
[5] C. Léveillé et al., Nat. Communication 13, 1412 (2022).

24Ultrafast Dynamics In Quantum Materials Using Time-resolved Resonant
Inelastic X-ray Scattering at SwissFEL Furka
Eugenio Paris, Hiroki Ueda, Elizabeth Skoropata, Biaolong Liu, Luc Patthey, Elia Razzoli
SwissFEL, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland
Author Email: Eugenio.paris@psi.ch
In the realm of strongly correlated materials with entangled degrees of freedom, accessing the ultrafast
dynamics involving different energy scales in a single experiment, with momentum resolution, promises
excellent scientific insight. Time-resolved Resonant Inelastic X-ray Scattering (tr-RIXS) emerges as aunique technique capable of unraveling such information. However, the full realization of its potential
has so far been limited by the available time- and/or energy resolution.
The soft-x-ray experimental endstation for condensed matter of SwissFEL - named Furka - aims toprovide state-of-the-art time-resolved RIXS/REXS experiments in combination with a widely tunable
pump laser radiation. Following the successful completion of the installation phase, Furka willcommence its user program in 2024.
In this presentation, I will provide an update on the status of the endstation and present results achievedin the early commissioning phase.

25

Theoretical study of magnetic excitations
in a photoexcited Mott insulator on a square latticeKenji Tsutsuia, Kazuya Shinjob, Shigetoshi Sotac, and Takami TohyamadaSynchrotron Radiation Research Center QST,b
RIKEN CEMS,c
RIKEN R-CCS,d
Dept. Appl. Phys. Tokyo Univ. Science
Author Email: tsutsui.kenji@qst.go.jp

Time-resolved L-edge resonant inelastic x-ray scattering (trRIXS) and time-resolved two-magnon
Raman scattering (trTMR) have been developed for investigating transient magnetic dynamics onstrongly correlated systems [1-3]. The photoexcitations of two-dimensional antiferromagnetic Mott
insulators have exhibited interesting phenomena such as weakened intensity of single- and two-magnon
excitations as observed in these pump-probe experiments.
In this study, we theoretically investigate magnetic dynamics in a photoexcited half-filled Hubbard
model on the square lattice [4]. We adopt a numerically exact-diagonalization technique on the finitesize square lattice to obtain time-resolved spin and two-magnon excitation spectra after a pump pulse.
We also examine momentum dependent two-magnon excitations after a pump pulse, which can beobserved in trRIXS. We find that new magnetic signals clearly emerge well below magnon energy inboth single- and two-magnon excitations when a pump pulse is tuned for an absorption edge.
Analyzing the wavefunction after a pump pulse in terms of the point group symmetry for the squarelattice, we find that photoinduced low-energy signals are predominantly created by a photoexcited statewith the E presentation of the C4v point group. Moreover, we find that an excitonic state of a holondoublon pair at the absorption edge plays an important role in enhancing the intensity of these excitations.
We expect that such characteristic pumping-frequency dependence will be observed in trRIXS andtrTMR experiments.
References[1] M. P. M. Dean et al. Nat. Mater. 15 601 (2016).
[2] D. G. Mazzone et al. Proc. Nat. Acad. Sci. USA, 118 e2103696118 (2021).
[3] J.-A. Yang, N. Pellatz, T. Wolf, R. Nandkishore, and D. Reznik, Nat. Commun. 11 2548 (2020).
[4] K. Tsutsui, K. Shinjo, S. Sota, and T. Tohyama, Commun.Phys. 6, 41 (2023).

26                 !$  " "!  # 
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+688-3):-,-3-+:8651+9?9:-49)5,8-)31@-15:81/;15//86;5,9:):-91-0-)<?.-841659)5,+0)8/-,-591:?
=)<-' (68-6<-8:0- ("1("--!-,1973)?9:0-01/0-9:A  )5,0)9:0-76:-5:1)3.684151):;81@-, 9715:8651+ ,-<1+-9 67-8):15/ ): 8664 :-47-8):;8- '  (  6=-<-8 1: 19 56: ?-: 256=5 1.
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 "0)8:1?)-:)3;57;*3190-,

27

Opportunities and challenges for the in-situ/operando soft X-ray
spectroscopy in energy, catalysis and chemical science
Jinghua Guo
Advanced Light Source, Lawrence Berkeley National Laboratory
Email: jguo@lbl.gov
The energy materials and devices have been largely limited in a framework of thermodynamic andkinetic concepts or atomic and nanoscale. Synchrotron based X-ray spectroscopic techniques offers
unique characterization in many important energy materials of energy conversion, energy storage andcatalysis in regards to the functionality, complexity of material architecture, chemistry and interactions
among constituents within. However, it is challenging to reveal the real mechanism of the chemical
processes. In the operando soft X-ray spectroscopy characterization of interfacial phenomena in energy
materials and devices, it has been found that the microstructure and composition of materials as well as
the microstructure evolution process have a great influence on performances in a variety of fields, e.g.,energy conversion and energy storage materials, chemical and catalytic processes.
This presentation will show how to best use the in-situ/operando soft X-ray spectroscopy
characterization techniques in the last two decades, including soft X-ray absorption spectroscopy (XAS)
and resonant inelastic soft X-ray scattering (RIXS) to investigate the real electrochemical mechanism
during the operation. The experimental results show how in-situ/operando soft X-ray spectra
characterization techniques uncover the phase conversion, chemical and environmental change ofelements and other very important information of solid/gas and solid/liquid interfaces in real time, thus
further enhance the understanding of real reaction mechanism. Some of the instrumentation
development will be presented in regards to the high throughput RIXS spectrometer on BL8.0.1 andnewly built RIXS beamline with a combination of in-situ/operando high-resolution and high-throughput
endstations on AMBER.
References[1] "Direct Observation of Two Electron Holes in a Hematite Photoanode during Photoelectrochemical Water
Splitting", A. Braun et al., J. Phys. Chem. C 116, 16870 (2012). DOI: 10.1021/jp304254k[2] "The structure of interfacial water on gold electrodes studied by x-ray absorption spectroscopy", J. J.
Velasco-Velez et al., Science 346, 831 (2014). DOI: 10.1126/science.1259437[3] "Soft x-ray spectroscopy of high pressure liquid", R. Qiao et al., Rev. Sci. Instrum. 89, 013114 (2018); DOI:
10.1063/1.5008444[4] "In-situ/operando X-ray absorption spectroscopic investigation of the electrode/electrolyte interface on themolecular scale", L.C. Kao et al., Surface Science 702, 121720 (2020). DOI: 10.1016/j.susc.2020.121720[5] "An optical design of soft x-ray spectrometer for imaging the catalytic reactions with resonant inelastic xray spectroscopy", Y.-D. Chuang et al., J. Synchrotron Rad. 27, 695 (2020). DOI:
10.1107/S1600577520004440

28

Resonant Inelastic X-Ray Scattering to study thin films of quantum
materials
Jonathan Pelliciari aaBrookhaven National Laboratory

Author Email: pelliciari@bnl.gov
The understanding of the interactions leading to the intriguing properties of quantum materials requires
the investigation of their elementary excitations in energy and momentum space. In this context,
Resonant Inelastic X-ray Scattering (RIXS) has emerged as a powerful probe with prime sensitivity to
the electronic (spin, orbital, and charge) and lattice degrees of freedom. Thanks to recent developments
RIXS has been employed in the investigation of many different systems, including cuprates, Fe-based
superconductors, and low dimensional magnets. One of the latest interests has been the investigation ofultrathin films and materials where the properties are markedly different than the bulk.
In my talk I will start by presenting of the current performance of the SIX beamline at NSLS-II andmove forward with our recent RIXS investigations in the field of thin films [1]. I will focus on two
different cases, the effect of confinement on the spin excitations of metallic iron [1], and the effect of
capping layer on superconducting infinite layer nickelates.
In the case of metallic Fe, the decrease of thickness affects anisotropically the three-dimensional spin
excitations of the bulk ferromagnet. In bulk-like films we corroborate the ability of RIXS to detectferromagnetic spin excitations and I will show a comparison with inelastic neutron scattering. As the
thickness is reduced, the out-of-plane spin excitations are gradually softened whereas the in-plane spin
excitations persist and retain their dispersion. Using several considerations, we can rule out phenomena
such as strain and substrate charge transfer and ascribe this evolution to confinement. Theoretically thistrend can be explained by conventional Heisenberg models accounting for the number of broken
magnetic bonds in proximity of the interface.
In second part of my talk, I will present the role of the capping layer for the excitations in parent NdNiO2
and optimal-doped Nd1-xSrxNiO2. In uncapped NdNiO2 compound we observe damped spin excitations
resembling the one observed in cuprates [2]. The intensity of the spin excitations is however strongly
decreased compared to the capped compound indicating a renormalization of magnetism. In
superconducting materials, independently of the presence of capping, we see an overall softening of thespin excitations compared to the parent compound. Overall, the spin excitations spectrum is suppressedin uncapped samples indicating a strong influence of the capping layer on the magnetism in infinite layer
nickelates regardless of doping. Remarkably, the spectral weight of the Ni-Nd charge transfer is also
highly suppressed. Finally, I will compare this experimental evidence in relation to previous calculations
accounting for the presence or lack of the capping layer.
References[1] J. Pelliciari et al. Nat. Mat. 20, 188 (2021)[2] H. Lu et al., "Magnetic excitations in infinite-layer nickelates", Science 373, 213 (2021)29                     
   

       &# #&#&& ")"#"*"(#" ')$&#")(#&''""(&)"",("'* -'()
&'&(#$ )&(&"'(#) "-'!) ("#)' -(&"( #&&$&!(&"(',((#"'"($'&!"('( +  (#)&&"(&'# )(#"&'#""(" '(,&-'((&"'()'#"( $"#!""#)  -&)$&(' &  )+&'"()&' #  ,((#"' "  "( " (  $#"#" &#'''(#"  "(&'(" -"#! #)'""!"('#( ,((#"'$"'(')$&#")("'((+&#'&*"&#$(!  #$" '$( ( ')$$&''#" # (  #&& $&!(&   - (&" (' "#! #)'(!$&()&$""(&#)#)(($'&!+"(-&(&'(#$"#""(&(#"#( $"#!" "')''('!$ (#"'#"$)((*%)"()!&( $#"('(!$&!('+  '#( #)(#)&&"('#*&-# """( -&" (')$&#")(#&' "')''
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30

Spin-excitation anisotropy in the nematic state of detwinned FeS
Thorsten SchmittaaPhoton Science Division, Swiss Light Source, Paul Scherrer Institut, CH-5232
Villigen PSI, Switzerland
Author Email: thorsten.schmitt@psi.ch
The origin of the electronic nematicity, which is characterized by rotational symmetry breaking, in FeSe
is one of the most important unresolved puzzles in the study of iron-based superconductors. In bothspin- and orbital-nematic models, the intrinsic magnetic excitations at Q1 = (1, 0) and Q2 = (0, 1) oftwin-free FeSe are expected to provide decisive criteria for clarifying this issue. Although a spinﬂuctuation anisotropy below 10 meV between Q1 and Q2 has been observed by inelastic neutron
scattering around Tc ∼ 9 K (<< Ts ∼ 90 K), it remains unclear whether such an anisotropy also persists
at higher energies and associates with the nematic transition Ts. Here we use resonant inelastic x-ray
scattering at the Fe L3-edge to probe the high-energy magnetic excitations of uniaxial-strain detwinned
FeSe [1]. A prominent anisotropy between the magnetic excitations along the H and K directions isfound to persist to ∼ 200 meV. This anisotropy decreases gradually with increasing temperature andﬁnally vanishes at a temperature around Ts. Our results reveal an unprecedented strong spin excitation
anisotropy with a large energy scale well above the dxz/dyz orbital splitting, suggesting that the nematic
phase transition is primarily spin-driven [1].
References[1] Xingye Lu, Wenliang Zhang, Yi Tseng, Ruixian Liu, Zhen Tao, Eugenio Paris, Panpan Liu, Tong
Chen, Vladimir Strocov, Yu Song, Rong Yu, Qimiao Si, Pengcheng Dai, and Thorsten Schmitt.
Nature Physics 18, 806–812 (2022).

31

Observation of the Flat Magnon Band in the Ferromagnetic Topological
Metal Fe3Sn2 by Resonant Inelastic X-ray Scattering
Wenliang Zhanga, Teguh Citra Asmaraa, Yi Tsenga, Junbo Lib, Yimin Xiongc, d, Vladimir N.
Strocova, Y. Sohe, Thorsten Schmitta, and Gabriel Aepplia, f, ga
Photon Science Division, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerlandb

Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High
Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, China
Department of Physics, School of Physics and Optoelectronics Engineering, Anhui
University, Hefei 230601, P. R. ChinacdHefei National Laboratory, Hefei 230028, China

Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerlandef

Laboratory for Solid State Physics and Quantum Center, ETH Zurich, CH-8093 Zurich,
Switzerland.
gInstitut de Physique, EPF Lausanne, CH-1015 Lausanne, Switzerland.
Email: wenliang.zhang@psi.ch

Magnetic metals with kagome structure can host various topologically non-trivial spin orelectronic states, providing an extraordinary platform for studying both the fundamental
topological physics and potential technological applications. The metallic kagome ferromagnet
Fe3Sn2, which has large spin-orbital coupling, shows considerable interplay between
magnetism and non-trivial electronic states1, 2. The material has a host of anomalous bulk
properties, including a first-order spin reorientation transition3, a large anomalous Hall effect4,
skyrmionic bubbles5, and field tunable nematic states1. Here, by applying circular polarized Xrays in resonant inelastic X-ray scattering (RIXS), we show that in ferromagnets excitations ofdifferent spin/orbital character present distinct magnetic circular dichroism (MCD) and can beselectively probed. Using the MCD RIXS and XAS (X-ray absorption spectroscopy), we report
the unambiguous isolation of magnetic signals of a flat spin wave band with large (comparedto elemental iron) orbital moments in Fe3Sn2. The flat mode energy is consistent with the highCurie temperature (𝑇𝑇C ≈ 640 K) as well as the strong acoustic mode dispersion, implying,
together with the substantial spin-orbit coupling indicated by the large orbital moment, that themode is topological6. The measured properties of the spin waves are highly unconventional andinclude very severe damping as well as a flat mode amplitude, which is maximized in the longwavelength limit where it is ordinarily expected to vanish. Our results illustrate how themagnetic circular dichroism analysis enhances the sensitivity of RIXS to magnetic excitations
in ferromagnetic materials and unveil an unconventional flat spin wave band in a kagome
ferromagnet.
Reference[1] J-X. Yin et al., Nature 562, 91–95 (2018);[2] M. Yao et al., arXiv:1810.01514 (2018);[3] K. Heritage, et al., Advanced Functional Materials, 1-12, 30(36), 2020[4] T. Kida, et al., J. Phys.: Condens. Matter 23 (2011) 112205;[5] Z. Zhou et al., Adv. Mater. 2017, 29, 1701144;[6] S A Owerre, J. Phys.: Condens. Matter 30 245803 (2018).

32

Expression and determination of the crystal electric ﬁeld
in the quantum spin-ice candidate Yb2Ti2O7
Octave Durosa,b , Christian Brouderb , Renaud Delaunaya , Hebatalla Elnaggarb , Romain Jarriera ,Haidong Zhouc , Amélie Juhinb , Gheorghe S. Chiuzbăiana
a Sorbonne Université, CNRS, Laboratoire de Chimie Physique - Matière et Rayonnement, LCPMR, F-75005 Paris,

France, b Sorbonne Université, Muséum National d’Histoire Naturelle, CNRS, Institut de Minéralogie, de Physique desMatériaux et de Cosmochimie, IMPMC, F-75005 Paris, France, c Department of Physics and Astronomy, Universityof Tennessee, Knoxville, TN 37996, USA
Author Email: octave.duros@sorbonne-universite.fr

Intensity (normalized)

Rare-earth titanate pyrochlores are deﬁned by the general chemical formula R2 Ti2 O7 (with R, a rareearth metal) and a distinctive crystalline structure, made of two interpenetrating tetrahedral networks. Oneof the most interesting aspects of the R2 Ti2 O7 compounds is the presence of fascinating magnetic phases,
such as spin-liquid or spin-ice states [1, 2]. The key ingredient for understanding such behaviors is thecharacterization of the crystal electric ﬁeld (CEF) acting on the R sites. Here, the CEF is created by thesurrounding oxygen ligands and interacts with the rare-earths 4f orbitals. Considering the D3d symmetryof the rare earths in R2 Ti2 O7 crystals, the CEF can be expressed as a function of six parameters Bkq in the
D3d= B20 C20 + B40 C40 + B43 (C4−3 − C43 ) + B60 C60 + B63 (C6−3 − C63 ) + B66 (C6−6 + C66 ),Wybourne convention [3]: HCEFkwith Cq the Racah tensor operators. In the more particular caseof Yb2 Ti2 O7 , a coexistence of ferromagnetic exchange interac1.0
Experimenttions with quantum ﬂuctuations was observed, which prevents
Bertin (2012)
0.8
any long-range ordering, leading to a so-called quantum spinDuros (2023)
ice state [4]. Among the pyrochlore family this compound is
0.6
one of the most intensively studied overtime, in particular using powerful inelastic neutrons scattering (INS) experiments
0.4[5, 6] that reach meV resolution. However, in practice, the de0.2
termination of CEF parameters is complicated by both the variety of CEF deﬁnitions available in the literature and the fact
0.0
that INS only probes the groundstate atomic manifold. Here,
−0.1
0.0
0.1
0.2
0.3
0.4
we propose an uniﬁed approach based on RIXS to complement
Energy transfer (meV)
INS data and pin down the 6 parameters involved in the CEF
Figure 1: RIXS measured (black points) andexpansion. Our strategy is motivated by the remarkable RIXS
calculated (dashed lines) spectra of the f-f
capabilities: the possibility to probe manifolds situated well excitations emphasizing the CEF effect inabove the groundstate and the resonant behavior of f-f inten- Yb2 Ti2 O7 . Calculations were performed in thesities. We recorded resonant spectra at the Yb N 4,5 edge by experimental conditions with two different setsusing the AERHA spectrometer [7] at SOLEIL and undertook of Bkq parameters.
RIXS calculations in Q UANTY within the ligand-ﬁeld multiplets approach [8] (see Fig. 1) to understand how the CEF affects the f-f excitations.
References[1] Borzi R.A. et al., Nat Commun 7 (2016), 1, 12592. doi:10.1038/ncomms12592[2] Bramwell S.T., Nat Commun 8 (2017), 1, 2088. doi:10.1038/s41467-017-02102-1[3] Wybourne B.G. et al., Spectroscopic Properties of Rare Earths, t. 18, American Institute of Physics (1965)[4] Robert J. et al., Phys. Rev. B 92 (2015), 6, 064425. doi:10.1103/PhysRevB.92.064425[5] Bertin A. et al., J. Phys.: Condens. Matter 24 (2012), 25, 256003. doi:10.1088/0953-8984/24/25/256003[6] Ruminy M. et al., Phys. Rev. B 94 (2016), 2, 024430. doi:10.1103/PhysRevB.94.024430[7] Chiuzbăian G.S. et al., Review of Scientiﬁc Instruments 85 (2014), 4, 043108. doi:10.1063/1.4871362[8] Haverkort M.W. et al., Phys. Rev. B 85 (2012), 16, 165113. doi:10.1103/PhysRevB.85.165113

33

Exciton delocalization mediated by charge-transfer dynamics in van der
Waals semiconductors
Connor A. Occhialinia, Yi Tsenga, Hebatalla Elnaggarb,c, Qian Songa,d, Mark Bleie, Sefaattin
Tongaye, Valentina Bisognif, Frank M. F. de Grootb, Jonathan Pelliciarif, Riccardo CominaaDepartment of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139,
USA, bDebye Institute for Nanomaterials Science, 3584 CG Utrecht, Netherlands, cSorbonne
Université, CNRS UMR 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimi,
4 Place Jussieu, 75005 Paris, France, dDepartment of Material Science and Engineering,
Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA, eMaterials Scienceand Engineering, School for Engineering of Matter, Transport and Energy, Arizona State University,
Tempe, Arizona 85287, USA, fNational Synchrotron Light Source II, Brookhaven National
Laboratory, Upton, New York 11973, USA
Email: tsengy@mit.edu
Excitons provide unique opportunities to understand low-energy dynamics in condensed matter, and areparticularly of recent interest in magnetic van der Waals (vdW) semiconductors. At this front, signatureof ultrasharp optical excitons have been reported in magnetically-ordered vdW materials hosting Ni2+
ions with small charge transfer gap, but a comprehensive understanding of their microscopic nature andconnection to magnetic order is still developing. Towards this goal, the momentum dispersion of exciton
quasiparticles has been shown to encode crucial insights into their inter-site propagation that governs
exciton properties. While this was previously demonstrated in organic semiconductors and alkali-metal
halides, such understanding is currently lacking for inorganic vdW semiconductors. Here, we study theultrasharp spin-flip excitations in the vdW triangular-lattice antiferromagnets NiX2 (X = Cl, Br, I) using
Ni L3-edge resonant inelastic X-ray scattering (RIXS). Varying the halogen allows systematically tuning
the charge-transfer energy and the magnetic ground state, to examine their roles in the exciton properties.
We reveal ultrasharp spin-flip excitations that exhibit nature of multiplets in a 3d8 electronic
configuration with octahedral ligand coordination. These modes are independent of the disparate
magnetic ground states and transition temperatures, as well as their respective spin excitation dispersions.
Notably, the observed spin-flip multiplets exhibit momentum-dispersion with a ligand-dependent
bandwidth based on a universal crystallographic periodicity, suggesting a charge-transfer exciton
character beyond the prototypical on-site inter-orbital dd transitions. From ligand-field and tight-binding
modelling, we determine an electronic dispersion driven by ligand-mediated third-nearest-neighbor
hopping processes on the 2D triangular lattice. Our momentum-resolved RIXS results broadly establish
the nature of spin-flip excitons unlimited to the optical dipole transitions, as well as their flexible
chemical tuning and design of delocalization pathways in magnetic vdW materials.

34

Spin-orbital excitations encoding the magnetic phase transition in the vander Waals antiferromagnet FePS3
Yi Tseng1,2, Hebatalla Elnaggar3, Yuan Wei1, Wenliang Zhang1, Teguh Citra Asmara1,
Eugenio Paris1, Gabriele Domaine2, Vladimir Strocov1, Luc Testa2, Virgile Favre2, Andrew
Wildes 4, Henrik Ronnow2, Frank de Groot5, Thorsten Schmitt1
1 Photon Science Division, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland, 2 Laboratory
for Quantum Magnetism, Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL),
Vaud, Switzerland, 3 Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590,
IRD, Institut de Minéralogie, 4 Institut Laue-Langevin, CS 20156, 38042 Grenoble C´edex 9, France,
5 Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CA
Utrecht, The Netherlands.
Author Email: yuan.wei@psi.ch
Magnetic van der Waals (vdW) materials have provided exciting new opportunities in the studies offunctional exotic magnetic phases of various symmetry-breaking groups. [1] The interlayer exchangeinteraction in these materials is very small, which allows for the decoupling of the magnetic layers andmakes it an ideal candidate for studying the effects of dimensionality and interlayer coupling on
magnetic behavior. [1] Recent studies utilizing primarily optical spectroscopy have demonstrated thesensitivity of the phonon spectral response to the magnetic state down to the few-layer limit. [2] Thishas opened up an opportunity for understanding and investigating the magnetic properties of thesematerials at the nanoscale.
FePS3 is one such vdW material that has garnered significant interest due to its uniquemagnetic and electronic properties. It is an S = 2 zig-zag quasi-two-dimensional antiferromagnetic
insulator with a honeycomb lattice. [3] The electronic structure of FePS3 has been resolved by various
techniques. X-ray absorption spectroscopy (XAS) has provided insights into how the local crystalline
environment shapes the anisotropic electronic structure. [5] Angle-resolved photoemission spectroscopy(ARPES) has been used to study the electronic band structure of FePS3, revealing the presence of spinsplit bands due to the strong spin-orbit coupling. [7]In this talk, resonant inelastic X-ray scattering (RIXS) has been used to study the spin-orbital
excitations of FePS3 and their relation to magnetism. By performing RIXS measurements as a functionof temperature across the magnetic transition, we reveal that the identified multiplets have a large
sensitivity to the spin state. Interestingly, the low-energy spin-orbital excitations in the presence ofmagnetic order are found to be strongly influenced by the trigonal lattice distortion and negative metalligand charge transfer, as revealed by simulation with ligand field theory calculations. This finding not
only relates to the fundamental physics of FePS3 but also establishes a generalized approach that is ideal
for studying magnetic functional materials and the relation between their low-energy electronic
properties and the magnetic state.
Beyond multiplets excitations, the RIXS spectra on vdW materials provide a rich platform forstudying a wide range of magnetic phenomena, including spin-orbit coupling, magnetic anisotropy, andspin excitations down to the monolayer level. This will open up exciting new avenues for the design anddevelopment of next-generation magnetic devices, such as spintronic and quantum computing
technologies.
References[1] H. Li et al. Adv. Mater. 31,1900065 (2019).
[2] K. Kim et al. Nanotechnology 30,452001 (2019).
[3] D. Lançon et al. Phys. Rev. B 94,214407 (2016)[4] J. Lee et al. Nano Lett. 16,7433–7438 (2016).
[5] X. Wang et al. 2D Mater. 3,031009 (2016).
[6] A. Chang et al Phys. Rev. B 106,125412 (2022)[7] X. Zhang et al. Adv. Sci. 2016, 3, 1600062 (2016)

35

Poster Presentation
Abstracts36

1

Presenter
Asakura,Daisuke

2

Fujii,
Kentaro3

Fujiwara,
Hidenori
Geprägs,
StephanHorio,
Masafumi
Jia,
Xun
Juhin,
AmélieLi,
Hao
Miyawaki,
Jun

4
5
6
7
8
9

10 Nakata,
Suguru11 Onishi,
Hiroaki
12 Soh,Jian-Rui
13 Takahashi,
Yoshihiro
14 Thomas-Hunt,Jack
15 Tomasello,
Bruno
16 Tomiyori,
Yusuke17 Yamaguchi,
Tatsuya
18 Yamasaki,
Yuichi19 Zhang,
Yujun
20 Su, Jia-Syuan

Poster Presentation List

Affiliation
National Institute ofAdvanced Industrial
Science andTechnology
National Institutes for
Quantum Scienceand Technology
Osaka University

Title
Transition-metal L-edge RIXS studies of cathodematerials for Li-ion batteries: Relation between
the charge-transfer effect and electrode
performance
Cu L-edge RIXS Spectra of Cu-Proteins

Probing spin-polarized electronic structures ofhalfmetallic Heusler alloys using RIXS-MCD
Walther-MeißnerControl of magnetic properties in iridate thin films
Institutby variation of strain and thin film thickness
University of Tokyo
Comparative RIXS investigation of five- and sixfold oxygen-coordinated 214-type cuprates
Chinese Academy of Orbital excitations on the cusp of Mott-band
Sciences
insulator crossover in 1T-TaS2
IMPMC-CNRS
Magnetic properties of binary ferrofluids
investigated by RIXS-MCD spectroscopy
University of Tokyo
The role of oxygen species on water uptake byhydrophobic materials
National Institutes for Construction of Ultrahigh Energy Resolution 2DQuantum Science
RIXS at NanoTerasu: Advancements and Current
and Technology
Progress
University of Hyogo
Charge order in cuprates revealed by resonant
inelastic x-ray scattering
Japan Atomic
Spin quadrupole excitations in frustrated
Energy Agency
ferromagnetic chain
Ecole Polytechnique Entangled spin-orbital-lattice order in Ba2MgReO6Federale Lausanne
Osaka Metropolitan
LDA+DMFT approach to resonant inelastic x-ray
University
scattering in strongly correlated magnetic
systems
Aarhus University
High resolution spin texture imaging in spin
caloritronics device structures: New opportunities
for REXS at 4th generation light sources.
University of Kent
Role of magneto-crystalline anisotropies incomplex rare-earth garnets
University of Tokyo
The Study on Water Repellent Behavior of
Hydrophobic Coatings by Soft X-ray
Spectroscopy
Osaka Metropolitan
Cu L3-edge resonant inelastic x-ray scattering on
University
isostructural copper oxides CaCu3Fe4O12 andEuCu3Fe4O12
National Institute for Anisotropic Magnetic Dipole Detectable byMaterials Science
Resonant X-ray Scattering
Chinese Academy of Hard X-ray High Energy Resolution Spectroscopy
Sciences
Beamline at High Energy Photon Source
National Yang Ming
Momentum-resolved RIXS studies on highChiao Tungtemperature superconductor Bi2212
University

37

Transition-metal L-edge RIXS studies of cathode materials for Li-ion
batteries: Relation between the charge-transfer effect and electrode
performance
Daisuke Asakura a,b,c, Eiji Hosono a,b,c, Yusuke Nanba a,#, Takaaki Sudayama a, Hisao Kiuchi
d,e, Hideharu Niwa d,e,†, Kosuke Yamazoe d,e, Jun Miyawaki d,e,‡, and Yoshihisa Harada c,d,eaResearch Institute for Energy Conservation, National Institute of Advanced Industrial Science andTechnology (AIST), Tsukuba, Japanbc

Global Zero Emission Research Center, AIST, Tsukuba, Japan

AIST-UTokyo Advanced Operando Measurement Technology Open Innovation Laboratory,
Kashiwa, Japande

Institute for Solid State Physics, The University of Tokyo, Kashiwa, Japan

Synchrotron Radiation Research Organization, The University of Tokyo, Kashiwa, Japan#

Present affiliation: Research Initiative for Supra-Materials, Shinshu University, Nagano, Japan†

Present affiliation: Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Japan‡

Present affiliation: Institute for Advanced Synchrotron Light Source, National Institutes for
Quantum Science and Technology (QST), Sendai, Japan
Author Email: daisuke-asakura@aist.go.jp

Resonant inelastic X-ray scattering (RIXS) is a promising tool for the electronic-structure analysis ofelectrode materials for Li-ion batteries (LIBs), in addition to X-ray absorption spectroscopy (XAS) and
X-ray photoemission spectroscopy. Particularly, RIXS at the O K-edge is attractive to investigate theoxygen redox in Li-rich layered oxides which are expected as candidates of high-capacity cathodematerials. Several groups have reported characteristic mechanisms about the oxygen redox by using O
K-edge RIXS [1-4].
On the other hand, we have applied transition-metal (TM) L-edge XAS and RIXS in
combination with multiplet calculations to various cathode materials to reveal not only the valence ofTM, but also the hybridization and charge-transfer (CT) effect to the O 2p orbitals. The detailed
information of the TM 3d and O 2p orbitals obtained by TM L-edge RIXS should be complementary toprevious knowledges mainly focused on the valence change of the TMs in prototypical cathode materials.
For example, the Mn L-edge RIXS and multiplet calculations for LiMn2O4 revealed very strong CT
effects for the Mn4+ in the charged state, which is much enhanced compared to the Mn3+ in theinitial/discharged state. Thus, the redox reaction of Mn3+/Mn4+ due to charge/discharge has a strong
covalent character with the O 2p orbital [5]. In contrast, the redox reaction of Fe2+/Fe3+ for LiFePO4 is
attributed to an ionic character. The analysis for the Fe L-edge RIXS spectra unveiled that the CT effectfrom the O 2p to Fe 3d orbitals is very weak for both Fe2+ and Fe3+ states [6]. The difference between
covalent/ionic characters possibly affects the structural stability on the TM-O bonds during chargedischarge, which should be related to the different cycle performances.
References[1] K. Luo et al., Nat. Chem. 8, 684 (2016).
[2] W. E. Gent et al., Nat. Commun. 8, 2091 (2017).
[3] T. Sudayama et al., Energy Environ. Sci. 13, 1492 (2020).
[4] R. A. House et al., Nature 577, 502 (2020).
[5] D. Asakura et al., Phys. Chem. Chem. Phys. 21, 18363 (2019).
[6] D. Asakura et al., ChemPhysChem 19, 988 (2018).

38

Cu L-edge RIXS Spectra of Cu-Proteins
K. Fujiia, b, Y. Izumia, J. Miyawakib, N. Kurahashic, H. Kiuchic, Y. Haradac, and M. Adachia
Institute of Quantum Life Science, National Institutes for Quantum Science and Technology
Advanced Synchrotron Radiation Center, National Institutes for Quantum Science and TechnologycSynchrotron Radiation Laboratory, The Institute for Solid State Physics, The University of Tokyoabfujii.kentaro@qst.go.jp
Amicyanine and Azurin are classified as Class I TICu proteins, whose axial ligand is the sulfur atomof methionine. Both protein molecules share the asymmetric structure of four amino acids, Met, Cys,
and two His, as the ligand for the copper atom. Azurin contains an additional second axial ligand in
addition to methionine in one axial position, as seen in the difference in distance to the oxygen atom.
Crystallographic analysis has revealed that this asymmetry differs by a few percent between azurin andamicyanine1. Their redox potentials differ by about 30 mV at pH 8.0. In addition, genetic recombination
technology has introduced both amino acid mutations, and significant redox potential changes of 500
mV or more have been observed when amino acid substitutions are introduced directly or indirectly at
the copper atom. Especially the changes of nearly 100 mV have been reported even at positions morethan 10 Å from the copper atom. In order to reveal these phenomena, we examined the resonant inelastic
soft X-ray scattering (RIXS) measurement of these solutions.
Soft X-ray emission spectra around Cu-Ledge were observed. These spectra were obtained using ahigh-resolution soft X-ray emission spectrometer HORNET2 installed at the end of the BL07LSU ofSPring-8. The apparent peak structures of each spectrum were observed. In order to assign these peakstructures, we are currently performing density functional theory simulations using a model moleculethat imitates the coordination of amino acids around Cu. Using DFT calculation, N.J. Fowler et al.
predicted reduction potentials for several Cu proteins containing mutants1. In the future, we plan toperform RIXS spectroscopy on mutants with different amino acid residues surrounding Cu or different
pH to obtain information on the correlation between the structure and electronic properties around Cu.
This information regarding copper proteins has valid for general use in biotechnology, such as enzymecatalyzed fuel cells or valorization of lignocellulosic biomass.
References[1] N.J. Fowler, C.F. Blanford, J. Warwicker, S.P. de Visser, Chem. Eur. J. 12 (2017) 15436-15445.
[2] Y. Harada et al., Rev. Sci. Instrum. 83 (2012) 013116.

39

Probing spin-polarized electronic structures of halfmetallic Heusler alloys
using RIXS-MCD
H. Fujiwaraa, R.Y. Umetsub, F. Kurodac, J. Miyawakid,e, A. Sekiyamaa, T. Oguchia,
Y. Haradad, and S. SugafaGrad. Sch. Eng. Sci., Osaka Univ., b IMR, Tohoku Univ., c CCS, Univ. Tsukuba,dISSP, Univ. Tokyo, e QST, f SANKEN, Osaka Univ.,

Author Email: fujiwara@mp.es.osaka-u.ac.jp
Toward the next-generation device development, the spintronics fully utilizing the spin-degrees of
freedom gathers wide attention. To design the spintronic devices, it is essential to optimize the spinpolarized electronic structures of the magnetic materials under the magnetic fields. Especially, the spinpolarization in the vicinity of the Fermi level (EF) for the conducting electrons and the size of spindependent band gap are key parameters in the magnetic layers, which are usually covered by capping
layers in the device. Resonant inelastic soft X-ray scattering (SX-RIXS), which is a photon-in/ photonout spectroscopy, is a suitable technique to investigate buried electronic structures with element specific
way by tuning the incoming photon energy to the core-level absorption edges [1,2]. Moreover, any
external perturbations, such as magnetic field, can be applied to study the electronic structures under theoperando conditions [3,4].
Recently, we established a versatile experimental technique to study the spin-polarized electronic
structures of the magnetic materials by using SX-RIXS at the transition metal (TM) 2p3/2 absorptionedge in an external magnetic field [5,6]. The effective magnetic field of the TM 3d states yields the spinpolarized 2p core states due to the effective Zeeman splitting, and thus the magnetic circular dichroism(MCD) in the SX-RIXS spectra can reveal the spin-polarized electronic structures thanks to thedominating selection-rule of the dipole-allowed transition between the core-level 2p states and the 3dstates for the circularly polarized light.
We applied this technique to probe the spin-polarized
electronic structures of halfmetallic Heusler alloys[5,6], in which one of the spin-subbands is metallic
and the other is semiconducting with a gap at the EF.
The half-metallic electronic structures of theferromagnetic Co2MnSi and ferrimagnetic Mn2VAl
are proved from the difference of the on-set energies
between the positive and negative MCD signals(Figs. 1(b), (d)), reflecting the up and down spincomponents in the valence band electronic structures,
respectively. Moreover, the RIXS-MCD allows us toconfirm which spin-subband is opened as thehalfmetallic gap, namely down and up spin gap inthese materials, respectively, giving the useful
information to design the spintronic devices.

Fig. 1 Intensity plot of the polarization averaged RIXS
and the RIXS-MCD data at the Mn 2p3/2 edge for
Co2MnSi in (a, b), and Mn2VAl in (c, d).

References[1] L. J. P. Ament, et al., Rev. Mod. Phys. 83, 705 (2011).
[2] F. Pfaff, H. Fujiwara, et al., Phys. Rev. B 97, 035110 (2018).
[3] J. Miyawaki, S. Suga, H. Fujiwara et al., J. Synchrotron Rad. 24, 449 (2017).
[4] J. Miyawaki, S. Suga, H. Fujiwara et al., Phys. Rev. B 96, 214420 (2017).
[5] R. Y. Umetsu, H. Fujiwara et al., Phys. Rev. B 99, 134414 (2019).
[6] H. Fujiwara, et al., Scientific Reports 11, 18654 (2021).

40

Control of magnetic properties in iridate thin films by variation of strain
and thin film thickness
S. Geprägsa, B. E. Skovdalb,c, M. Scheufelea,d, H. Muzychkoa,d, D. Wermeillee, P. Thompsone,
A. Efimenkof, A. Bombardig, D. L. Quintero-Castroh, R. Grossa,d,i, D. Mannixj,kaWalther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching, Germany, bDivisionof Synchrotron Radiation, Lund, Sweden, cAngstrom Center, Uppsala, Sweden, dTechnische
Universität München, TUM School of Natural Sciences, Garching, Germany, eXMaS CRG Beamline,
ESRF, Grenoble, France, fEuropean Synchrotron Radiation, Grenoble, France, gDiamond Light
Source, Harwell Science & Innovation Campus, Didcot, United Kingdom, hDepartment ofMathematics and Physics,University of Stavanger, Stavanger, Norway, iMunich Center for Quantum
Science and Technology, Munich, Germany, jEuropean Spallation Source, Lund Sweden, kAarhus
University, Aarhus, Denmark
Author Email: Stephan.Gepraegs@wmi.badw.de
The complex 3d transition-metal oxides are one of the most fascinating and technologically relevantmaterial systems, with a plethora of physical properties. The 5d transition-metal compounds offer the
potential to further enrich the physics of this class of materials, as one can generate new physicalproperties by making use of strong spin-orbit coupling. To this end, the Ruddlesden-Popper series
Srn+1IrnO3n+1 has attracted considerable scientific attention due to the possibility of generating spin-orbit
driven Mott insulating states [1]. In the first member of this series, the layered Sr2IrO4 (SIO-214)
compound, the large spin-orbit coupling combined with a moderate Coulomb repulsion result in a Mott
insulating 𝐽𝐽eff = 1/2-ground state, which is similar to the 𝑆𝑆 = 1/2-ground state of high-temperature
superconducting Cu-oxides. Additionally, the second member of the series, the bilayer Sr3Ir2O7 (SIO327), exhibits an antiferromagnetic excitonic insulating state [2]. To investigate the impact of strain andfinite size effects on the magnetic properties of these compounds, we present a comprehensive study of
epitaxially-strained SIO-214 and SIO-327 thin films. By using X-ray resonant scattering (REXS), weshow that the out-of-plane magnetic correlation length of SIO-214 thin films is strongly dependent on
the thin film thickness, but independent of the strain state of the thin films (see Fig. 1) [3]. Resonant
inelastic X-ray scattering (RIXS) further demonstrates that strained SIO-214 thin films exhibit similar
exchange constants than bulk SIO-214, while strained SIO-327 thin films clearly show a modified interlayer coupling and enhanced anisotropic interactions mainly caused by finite size effects.
These results provide a clearer picture for the systematic control of the magnetic degrees of freedom inepitaxial thin films of SIO-214 and SIO-327 and highlight the potential for a rich playground, allowing
to explore the physics of 5d transition-metal compounds.

Figure 1: Out-of-plane correlation length as afunction of SIO-214 film thickness deduced
from REXS measurements [3].

Figure 2: Single magnon dispersion of a SIO214 thin film derived from RIXS measurements
and Spin-W simulations.

References[1] B. J. Kim et al., Science 323,1329 (2009).
[2] D. G. Mazzone et al., Nat. Comm. 13, 913 (2022).
[3] S. Geprägs et al., Phys. Rev. B 102, 214402 (2020).

41

Comparative RIXS investigation of five- and six-fold oxygen-coordinated214-type cuprates
Masafumi Horioa, Xie Peiaob, Jaewon Choic, Masashige Miyamotoa, Kaede Isomurab, Mirian
García-Fernándezc, Ke-Jin Zhouc, Takanori Taniguchib, Masaki Fujitab, Iwao MatsudaaaInstitute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan,bInstitute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japanc
Diamond Light Source, Harwell Campus, Didcot OX11 0DE, United Kingdom
Author Email: mhorio@issp.u-tokyo.ac.jp

Identifying the governing principle of transition temperature (Tc) is a central issue of high-temperature
superconductivity in cuprates. The electronic structure of the so-called 214-type cuprate La2-xSrxCuO4(LSCO) has been intensively studied to understand the mechanism of its low Tc. A short distance
between CuO2 planes and apical oxygen atoms is suggested detrimental for superconductivity in LSCO
from several perspectives. First, small crystal-field splitting between the dx2-y2 and dz2 orbitals cause
orbital hybridization and hence dilution of orbital characters around the Fermi level [1,2]. The shortapical-oxygen distance also results in the increase of the charge-transfer gap and thus effective on-site
effective Coulomb interaction U. It was suggested using the Hubbard model that larger U for LSCO
facilitates tendency toward charge ordering, which competes with superconductivity and could in turnlower Tc [3].
While La2-xSrxCuO4 normally has six-fold octahedral oxygen coordination around Cu (T-type structure,
Fig. 1), 214-type cuprates can also crystalize with five-fold pyramidal coordination (T*-type structure,
Fig. 1) [4]. The lack of one apical-oxygen atom is expected to enhance crystal-field splitting and reducethe charge-transfer gap [5]. These changes would alleviate degradation of superconductivity, and,
therefore, straightforward consideration predicts higher Tc for the T*-type cuprates. However, maximum
Tc of the T*-type cuprates is even lower than that of the T-type counterpart [6]. Closer investigations of
the electronic structure of the T*-type cuprates are thus desired.
We have performed comparative Cu L-edge RIXS studies for the T- and T*-type cuprates at DiamondLight Source beamline I21. The dz2 component of the dd excitation was observed at significantly higher
energy for the T*-type cuprate, indicating larger crystal-field splitting between the two eg orbitals. As
previously reported for multi-layer cuprates with five-fold oxygen coordination [7], larger magnondispersion anisotropy was found for the T*-type cuprate along the (, 0) and (, ) directions. Oncehole-doped, a signature of charge ordering was observed for the T*-type cuprate but with much lesspronounced manner than the case of the T-type cuprate. While
the above aspects should be in favor of higher-temperature
superconductivity, the magnon band width governed by thenearest-neighbor exchange was smaller for the T*-type
cuprate, which may act negatively on Tc [8]. The results
suggest the delicate valance of multiple interactions governing
the Tc of the 214-type cuprates.
References[1] H. Sakakibara et al., Phys. Rev. Lett. 105, 057003 (2010).
[2] C. E. Matt et al., Nat. Commun. 9, 972 (2018).
[3] M. Imada, J. Phys. Soc. Jpn. 90, 111009 (2021).
[4] J. Akimitsu et al., J. Appl. Phys. 27, L1859 (1988).
[5] Y. Tokura et al., Phys. Rev. B 41, 11657 (1990).
[6] T. Kakeshita et al., J. Phys.: Conf. Ser. 150, 052089 (2009).
[7] Y. Y. Peng et al., Nat. Phys. 13, 1201 (2017).
[8] L. Wang et al., Nat. Commun. 13, 3163 (2022).

Fig.1: Crystal structure of the T(left) and T*-type (right) cuprates.

42

Orbital excitations on the cusp of Mott-band insulator crossover in 1T-TaS2
Xun Jia 1a, b, Yue Cao 2a,abMaterials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA

Multi-disciplinary Research Division, Institute of High Energy Physics, Chinese Academy of
Sciences, Beijing 100049, China
Author Email: jiaxun@ihep.ac.cn

The nature of electron itinerancy is a fundamental descriptor of a solid-state material. In the case of
insulators, band and Mott insulators represent two drastically different regimes: the former can be
described using spatially extended electron wavefunctions and well-defined quasiparticles, while thelatter features localized electron wavefunctions with strong local correlations. Recently the nature of theinsulator behavior has been under intense investigation in a number of 5d transition metal com-pounds
due to the more extended nature of the 5d orbital wavefunction, where direct experimental observations
are expected urgently. Here we perform resonant inelastic X-ray scattering studies of 1T-TaS2 which
has till recently been long considered a prototypical Mott insulator. We observed five electronic
excitations arising from the interband transitions of the Ta 5d/5p orbitals and the S 3p ligand state at theTa L3 edge. These excitations cannot be explained within the framework of standard molecular orbital
multiplet calculations that are based on a localized picture with strong electronic correlations. Instead,calculations from the band dispersions can reasonably capture the number and energies of the orbital
excitations with small deviations. We argue that the insulating phase of 1T-TaS2 is on the cusp of bandMott insulator crossover and leans heavily towards the band insulator limit[1].
Our discovery provides new insight into the Mott vs. band insulator debate in 1T-TaS2 and other 5dtransition metal materials and puts RIXS as a new tool capable of detecting the orbital excitations inmaterials with weaker electron correlation and localizations.
Acknowledgments
The work at Argonne was supported by the U.S. Department of Energy, Office of Science, Basic
Energy Sciences, Materials Science and Engineering Division.
References[1] X. Jia et al., arXiv:2210.01181 (2022).

43

Magnetic properties of binary ferrofluids investigated by RIXS-MCD
spectroscopy
Malika Khelfallah,a Sophie Neveu,b James Ablett,c Vincent Dupuis,b Niéli Daffé,a,b,c Guillaume
Gouget,a,b Marcin Sikora,d Philippe Sainctavit,a Hebatalla Elnaggar,a Claire Carvallo,a Dario
Taverna,a Amélie Juhinaa

IMPMC, UMR CNRS 7590, Université Pierre et Marie Curie, 4 Place Jussieu, 75005 Paris, France
PHENIX, UMR 8234, Université Pierre et Marie Curie, 4 Place Jussieu, 75005 Paris, France,cSynchrotron SOLEIL, L’Orme des Merisiers, 91190 Saint Aubin, France,d
AGH University of Science and Technology, 30-059 Kraków, Poland,bAuthor Email: malika.khelfallah@sorbonne-universite.fr
Ferrofluids are suspensions of magnetic nanoparticles in a liquid, which have found numerous
applications in biomedicine (magnetic hyperthermia, improved MRI agents…), technology (magnetic
recording, permanent magnets…) or fine arts. Intriguing macroscopic properties of ferrofluids arise
from their nanoscale structuring: when the magnetic dipolar interparticle interaction are large enough,particles assemble in chains and rings even in the absence of a magnetic field. These assemblies turninto microsized chains when an external magnetic field is applied. Variation of the nanoparticle size,
shape and composition (e.g., hard or soft magnetic material) changes the magnetic anisotropy, whichplays a crucial role in magnetic dipole interactions. This results in a modification of the structuring of
ferrofluids as well as their collective magnetic properties like coercivity, magnetic saturation or
remanence.
Understanding and controlling interparticle interactions could lead to improving the efficiency ofknown ferrofluids for applications and the discovery of novel magnetic responsive materials. Magnetic
binary ferrofluids, i.e. those composed of two types of nanoparticles with different magnetic anisotropy,
are particularly appealing because they offer an unprecedented interplay of magnetic dipole interactions.
However, bulk magnetometry only allows to probe the average magnetic properties of the ferrofluid,which preventing from selectively measuring the contribution of each component. There is therefore aneed for chemically selective magnetic measurements, which can be realized using Resonant Inelastic
X-ray Scattering spectroscopy combined with X-ray Magnetic Circular Dichroism with hard x-rays(RIXS-MCD, [1]).
Element selective magnetization curves detected by RIXS-MCD have been measured at the
GALAXIES beamline of the SOLEIL synchrotron on binary ferrofluids with different particle size,
shape and composition. Zero Field Cooled and Field Cooled magnetic measurements have been
performed to investigate how the structuring induced by an external magnetic field modifies themeasured collective properties. Ferrofluid samples have been measured in the frozen state using a
dedicated cryo liquid cell [2] which is inserted between the poles of an electromagnet. RIXS-MCD
experiments are complementary to bulk magnetometry and First Order Reversal Curve diagram
measurements of collective magnetic properties. Combined with the information obtained from
Cryogenic Transmission Electron Microscopy and Electron Holography regarding the structuring, ourresults pave the way for a better understanding of the relationship between magnetic properties andstructuring of binary ferrofluids.
References[1] M. Sikora, A. Juhin, T.-C. Weng, P. Sainctavit, C. Detlefs, F. de Groot and P. Glatzel. Physical Review
Letters, 105,037202 (2010).
[2] N. Daffé, J. Zečević, K. N. Trohidou, M. Sikora, M. Rovezzi, C. Carvallo, M. Vasilakaki, S. Neveu, H.
Meeldijk, N. Bouldi, V. Gavrilov, Y. Guyodo, F. Choueikani, V. Dupuis, D. Taverna, Ph. Sainctavit, and A.
Juhin. Nanoscale 12, 11222-11231 (2020).

44

The role of oxygen species on water uptake of Cyclic Olefin Polymers
Hao Lia, Mustafa Samaraib, Yuki Nakamac, Satoru Adachic, Kenji Kuroyanagic,
Kiuchi Hisaoa,b*, Yoshihisa Haradaa,b*aGraduate School of Frontier Sciences, The University of Tokyo, Japan, bInstitute for Solid State
Physics, The University of Tokyo, Japan, cZeon Corporation, Japan*kiuchi@issp.u-tokyo.ac.jp, harada@issp.u-tokyo.ac.jp
Currently, super hydrophobic material withrelatively low water absorption property has
gained considerable interest due to their wide
range of applications to blood contacting
devices. Within this context, a prominent
candidate is a series of Cyclic Olefin
Polymers (COPs) which are formed of the Figure 1. Typical molecular structure of COPs. Depending
alternating repeating units of ethylene and on the combination of R1, R2, X, Y and Z, COPs exhibit
five membered ring with various side groups. different functionalities.
(Figure 1). COPs have a low water absorption
property (<0.01%), four times less than polycarbonate and 10 times than poly-methyl methacrylate(PMMA) even in high humidity environment.
The high biocompatibility of COPs results from its high hydrophobic nature following theinteractions with living cells, which reduce side effect and facilitates the normal flow of blood andplasma. In addition, Anti-fouling property of super hydrophobic surface could prevent the attachmentof organic substances and microorganism. These attributions are critical to medical applications suchas filter membranes, prosthetic heart valves, drug eluting stents (DES), and extracorporeal membrane
oxygenation (ECMO), which is used for oxygen therapy for critical patient suffering from COVID-19.
Furthermore, due to their verified hemocompatibility and low cytotoxicity [1], COPs also have goodpotential as biomaterial for drug delivery and bio-interface. However, the mechanism of
biocompatibility in the superhydrophobic COPs has not been fully understood under in detail andneeds extensive studies.
The purpose of this study is to understand hydrogen-bonded structure of water and ratios ofadsorbed water phases during humidification of the strongly hydrophobic COPs, which should be
responsible for biocompatibility. A combination of O K-edge X-ray Absorption (XAS), Oxygen 1s
X-ray emission (XES), and X-ray Photoelectron Spectroscopy (XPS) was used to unravel the nature of
the oxygen species generated during the humidification treatment and clarify the mechanism of
biocompatibility. The absorption of water on the hydrophobic surface is energetically not favorable
and proceeded through a stepwise process. At the low relative humidity regime (<90% RH), it was
found that water absorbed rather in an isolated domains on the hydrophobic COP surface. For
RH>95% the saturation level is surpassed and the majority of absorbed water on the COP surface has
a disordered bulk like water structure. Based on the pre-edge feature in the XAS spectrum, theexistence of carbonyl group, peroxide and hydroxide species on the redried COP film was observed.
This implies that in addition to the interaction between the bare hydrophobic COP surface and water,
the slight hydrophilicity introduced by the oxygen functional groups created on the COP surface may
contribute to the COP's biocompatibility.
Acknowledgement

This work was performed in collaboration with and financially supported by ZEON Corporation.
References[1] Schossleitner K et al., J Biomed Mater Res A, 107(3): 505-512 (2019).

45

Construction of Ultrahigh Energy Resolution 2D-RIXS at NanoTerasu:
Advancements and Current Progress
Jun Miyawaki, Kohei Yamamoto, Kentaro Fujii, Koji Horiba, Hideaki Iwasawa,
Yoshiyuki Ohtsubo, Miho Kitamura, Takashi Imazono, Tomoyuki Takeuchi, Nobuhito Inami,
Takeshi Nakatani, Kento Inaba, Akane Agui, Hiroaki Kimura, and Masamitu Takahasi
Institute for Advanced Synchrotron Light Source, National Institutes for Quantum Science and Technology,
Sendai, Japan

Author Email: miyawaki.jun@qst.go.jp
Resonant inelastic X-ray scattering (RIXS) is a powerful technique for studying the energies ofelectronic states and elementary excitations in materials by analyzing the energy of X-rays scattered off
matter. Recent advances in energy resolution have enabled around 30 meV energy resolution at the Cu
L edge [1,2], making RIXS an increasingly important tool in materials science. However, to observe
lower-energy excitations, even higher energy resolution is desired. Thus, efforts are underway toenhance the resolution of RIXS measurements through different approaches.
At NanoTerasu in Tohoku, Japan, we are currently constructing an ultrahigh energy resolution
RIXS facility. This advanced facility consists of a dedicated beamline [3] and a 2D-RIXS spectrometer.
Our goal is to achieve a total energy resolution (combined resolution of the beamline and RIXS
spectrometer) of sub-10 meV below hv=1000 eV. To achieve such ultrahigh energy resolution, we
employed the hv2-concept [4,5] for our RIXS spectrometer, to compensates for the reduced
measurement efficiency inherent in enhancing energy resolution.
Figure 1 shows the optical layout of the 2D-RIXS facility. The beamline and the 2D-RIXS
spectrometer span ~76 m and ~12 m, respectively, and the RIXS spectrometer is planned to have a 2θrotation range of 30–150°. The beamline has no exit slit, and vertically energy-dispersed X-ray fromthe beamline monochromator is directly irradiated onto a sample. The RIXS spectrometer features animaging mirror that collects scattered X-rays from the sample and images them onto a detector while
maintaining the relationship between the vertical position and the incident energy. Simultaneously, thegrating in the RIXS spectrometer disperses and focuses thescattered X-rays horizontally onto the detector. Thus, theenergies of the incident and scattered X-rays are “twodimensionally” resolved on the detector, which is why we call
“2D-RIXS”. By integrating the intensity of the spectra along
the incident energy, we can improve measurement efficiency.
In the poster, we will provide an overview of the
optical design of the 2D-RIXS facility and discuss ourefficiency improvements.

Figure 1: Schematic representation of the optical layout of
ultrahigh resolution 2D-RIXS facility at NanoTerasu.
References[1] N. B. Brookes et al., Nucl. Instrum. Methods A 903, 175 (2018).
[2] K.-J. Zhou et al., J. Synchrotron Rad. 27, 1235 (2020).
[3] J. Miyawaki et al., J. Phys. Conf. Ser. 2380, 012030 (2022).
[4] V. N. Strocov, J. Synchrotron Rad. 17, 103 (2010).
[5] K.-J. Zhou et al., J. Synchrotron Rad. 27, 1235 (2020).

46

Charge order in cuprates revealed by resonant inelastic x-ray scattering
Suguru Nakataa,b, Davide Bettoc, Federico Pisanic, Chengtian Linb, Roberto Santc, Kurt
Kummerc, Nicholas B Brookesc, Bernhard Keimerb, Matteo MinolabaUniversity of Hyogo, bMax Planck Institute for Solid State Research, cEuropean Synchrotron
Radiation Facility (ESRF)
Author Email: nakata@sci.u-hyogo.ac.jp

I will present recent results on charge ordering, which strongly competes with high-temperature
superconductivity, in underdoped cuprates investigated by Cu L edge (931.5 eV) resonant inelastic xray scattering (RIXS) experiments carried out at the beamline ID32 of the European Synchrotron
Radiation Facility (ESRF) in Grenoble, France. In particular, we focused on one particular member ofthe cuprate family, i.e., the stoichiometric, nearly-disorder free high-temperature superconductor
YBa2Cu4O8 (Y124). We find charge ordering qualitatively akin to that observed in non-stoichiometric
YBa2Cu3O6+x (Y123), which has been extensively studied as a model system for charge ordering in
cuprates. However, the temperature evolution of the charge order of Y124 is distinct from the ’gradualfreezing’ of Y123, albeit the finite correlation length persisting even at the lowest temperature indicatesa short-range nature of the charge order in Y124 as well. Interestingly, the onset temperature of thecharge order was found to match the temperature of the charge-transport anomaly. In this framework ofconnecting transport and charge order, I will also address the uniaxial stress response of the transportcoefficients in Y123, which show a remarkable correspondence with the onset of charge order [1].
Our findings establish the presence of charge ordering in Y124 and provide new insights into therelationship between disorder, charge-ordering formation, and other prominent phenomena inunderdoped cuprates.
References[1] S. Nakata et al., npj Quantum Mater. 7, 118 (2022).

47

Spin quadrupole excitations in frustrated ferromagnetic chain
Hiroaki Onishi
Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
onishi.hiroaki@jaea.go.jp
Frustrated quantum magnets frequently exhibit non-trivial ground states that do not have a classicalanalogue, since the combined effects of frustration and quantum fluctuations destroy conventional
magnetic order. The spin nematics, characterized by spin quadrupoles, is a prominent example. Here,
we focus on a spin nematic liquid state in a frustrated ferromagnetic chain with nearest-neighborferromagnetic and next-nearest-neighbor antiferromagnetic exchange interactions in a magnetic field.
To clarify the property of the spin nematic liquid state from the viewpoint of excitation dynamics, wehave studied excitation spectra by dynamical density-matrix renormalization group methods [1,2,3,4].
In the spin nematic regime at high magnetic fields, we find gapless longitudinal and gapped transverse
spin excitation spectra, in accordance with quasi-long-range longitudinal and short-range transverse spincorrelations, respectively. Moreover, in the quadrupole channel, we observe gapless excitations at q=p,signaling quasi-long-range antiferro-quadrupole correlations. These characteristics of excitation spectra
are useful and essential to identify the spin nematic state by experiments in real compounds. However,conventional magnetic probes are usually insensitive to spin quadrupoles. In this context, based onsymmetry arguments, it has been suggested that resonant inelastic x-ray scattering (RIXS) would
provide a route to detect quadrupole excitations [5,6]. We will present detailed numerical results ofquadrupole excitation spectra and discuss possible relevance to RIXS.
References[1] H. Onishi, J. Phys. Soc. Jpn. 84, 083702 (2015).
[2] H. Onishi, J. Phys.: Conf. Ser. 592, 012109 (2015).
[3] H. Onishi, Physica B 536, 346 (2018).
[4] H. Onishi, J. Phys.: Conf. Ser. 2207, 012045 (2022).
[5] M. W. Haverkort, Phys. Rev. Lett. 105, 167404 (2010).
[6] L. Savary and T. Senthil, arXiv:1506.04752.

48

Entangled spin-orbital-lattice order in Ba2MgReO6
Jian-Rui Soha, Jana Pásztorováa, Sonia Francoualb, Kenji Ishiic, Yuan Weid, Carlos W.
Galdinod, Daigorou Hiraie, Andrea Urruf, Sayantika Bowalf, Ivica Živkovića, Aria M.
Tehranig, Davor Tolja, Nicola A. Spaldinf, Thorsten Schmittd, Henrik RønnowaaEPFL, Switzerland, bDESY, Germany, cSPRING-8, Japan, dSLS, Switzerland, eNagoya University,
Japan, fETHZ, Switzerland, gMIT, USA
jian.soh@epfl.ch

Quantum materials which exhibit an intimate coupling between the local structural distortions, magnetic
dipoles and charge quadrupoles have generated sustained interest because they have the potential to giverise to new exotic phases of matter such as quantum spin liquids, axion insulator etc. In cases where thecoupling between the lattice, spin, and orbital degrees of freedom is particularly strong, these entities
become deeply intertwined, and cannot be considered as separate components.
The long-range order of such local entangled states can be stabilized in 5d1 double perovskite (DP)systems, owing to the comparable lattice strain, spin-orbit coupling, electron correlations and magnetic
exchange energies. One such example of a realization is in the 5d1 DP Ba2MgReO6, which displays two
successive anomalies at TQ and TM, which demarcate three distinct phases [1].
Using a combination of REXS at the Re L3 edge (DESY, Germany), RIXS at the Re L3 edge (Spring-8,Japan), RIXS at the O K edge (SLS, Switzerland), density functional theory (DFT) calculations, quantum
chemistry (QC) calculation and heat capacity measurements at high field (30 T), we find mounting
evidence for a highly coupled spin-orbital-lattice eigenstate in Ba2MgReO6.
Our REXS results show that below TQ, Ba2MgReO6develops anti-ferroic order of eigenstates composedof an entanglement between the rhombic in-planemovement of oxygen ligands (green arrows in
Figure) and an ordering of Re 5d1 Qxy charge
quadrupoles. Simultaneously, we also find that thereis ferroic order of eigenstates composed of anentanglement between the apical movement ofoxygen ligands (blue arrows in Figure) and anordering of Re 5d1 Qz2 charge quadrupoles.
Our RIXS measurements indicate that this entangled
eigenstate arises from an inherent coupling between
the structural and charge degrees of freedom.
Moreover, our QC and DFT calculations show thatthe entanglement between these degrees of freedom
are the lowest energy ground state of the system,
which accounts for why they work cooperatively.
Hence, our results verify the mean-field models [2-4], dynamical mean-field [5] and density functional
calculations [6-8] which all predict charge quadrupolar order of 5d1 ions in DP systems. Furthermore,
we make a case for a single order parameter composed from an intimate coupling between the spinorbital and lattice degrees of freedom.
References[1] Hirai, H. et al., Phys. Rev. Research 2, 022063 (2020).
[2] G. Chen, R. Pereira, and L. Balents, Phys. Rev. B 82, 174440 (2010).
[3] G. Chen and L. Balents, Phys. Rev. B 84, 094420 (2011).
[4] C. Svoboda, W. Zhang, M. Randeria, and N. Trivedi, Phys. Rev. B 104, 024437 (2021)[5] V. Pourovskii, D. F. Mosca, and C. Franchini, Phys. Rev. Lett. 127, 237201 (2021).
[6] Iwahara, V. Vieru, and L. F. Chibotaru, Phys. Rev. B 98, 075138 (2018).
[7] A. M. Tehrani and N. A. Spaldin, Phys. Rev. Mater. 5, 104410 (2021).
[8] R. Cong, R. Nanguneri, B. Rubenstein, and V. F. Mitrovic, Phys. Rev. B 100, 245141 (2019)49

LDA+DMFT approach to resonant inelastic x-ray scatteringin strongly correlated magnetic systems
Y. Takahashia, J. Kunešb, A. HarikiaaDepartment of Physics and Electronics, Osaka Metropolitan University,
1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan,bInstitute of Solid State Physics, TU Wien, 1040 Vienna, Austria
sb22047r@st.omu.ac.jp

Resonant inelastic x-ray scattering (RIXS) has become a valued tool for studying materials withstrongly correlated electrons, such as transition metal compounds, thanks to a remarkable improvementof the energy resolution in the last decade. Though RIXS has a broad sensitivity to excitations of spin,
orbital, and charge degrees of freedom, its drawback is often complicated experimental spectrum, whichcalls for its theoretical modelling. For strongly correlated electron systems, impurity models, such as
cluster model including an excited metal site and its surrounding ligands, have been widely used for the
spectral analysis. However, since band excitations are lacked in the cluster model, a disentanglement of
the localized and delocalized RIXS features is prohibited. Band-structure approaches for RIXS often
suffer from difficulties in incorporating the strong correlation effects. In this context, recently, we
introduced an ab-initio method based on local density approximation (LDA) + dynamical mean-field
theory (DMFT) for modelling RIXS spectra of strongly correlated electron systems [1,2]. In this method,
DMFT supplements electron correlation effect to the material specific bands provided by LDA. Thus,
the LDA+DMFT method allows us to describe continuum of band excitations (with unbound electronhole pairs) as well as bound excitations (such as intraatomic multiplet excitations) simultaneously.
In this work, we apply the LDA+DMFT method to study magnetic and orbital excitations in twocorrelated magnetic systems Fe2O3 and RuO2 of much recent attention. For Fe2O3, an antiferromagnetic
Mott-insulator with a large spin degrees of freedom S=5/2, we present a detailed comparison with thehigh-resolution RIXS at the Fe L3-edge and reveal the energy dispersion as well as the excitation
mechanism of higher-order magnons [3]. For RuO2, a representative compound of altermagnetic system[4], we will discuss possible magnetic circular dichroism in M-edge x-ray absorption spectroscopy and
RIXS, and its relation to the unique spin properties in this material.

References[1] A. Hariki et al., Phys. Rev. B 101, 115130 (2020).
[2] A. Hariki et al., Phys. Rev. Lett. 121, 126403 (2018).
[3] J. Li et al., Phys. Rev. X 13, 011012 (2023).
[4] L. Šmejkal et al., arXiv:2211.13806 (2022).

50

High resolution spin texture imaging in spin caloritronics device structures:
New opportunities for REXS at 4th generation light sources.
Jack Thomas-Hunta, Paul Evansb, Virginie Chamardc, Dina Carboned, Peng Lie, Stephan
Geprägsf, Danny Mannixi.
aAarhus University, Denmark., bUniversity of Winconsin, WI. USA., cInstitut Fresnel, CNRS Marseille,
France., dMax-IV, Lund, Sweden., eDiamond Light Source, Oxfordshire, UK., fWalther Meissner
Institut, Munich, Germany., iESS, Lund, Sweden.
Author Email: jth@chem.au.dk

The rare earth iron garnets (RIG), since conception have required novel probes to understand theirmagnetic properties, e.g. neutron diffraction. The recent renaissance in RIG research is being driven by
their potential in novel spin (calori)tronic [1] devices. The development of emerging nanotechnologies
exploiting spincaloritronic physics, requires new microscopic tools to reveal how atomic structure andmagnetism are related at the nanoscale. The advent of new 4th generation synchrotron sources, such as
the ESRF EBS, promise to deliver higher coherence and higher flux focused X-ray beams, to meet theknowledge demands for 21st century technologies. Recent advancements in REXS with x-ray

nanobeams at the ESRF have revealed spin textures [2], responsible for degrading thethermoelectric efficiency of the SSE, with high spatial resolution. Here, we present new
nanobeam diffraction results from the new ESRF EBS, where we demonstrate an increase inspatial resolution from 400nm to 80nm. Furthermore, the expansion of these imaging
techniques to combine REXS and Bragg ptychography methods, with a potential spatial
resolution of 16nm, will also be presented.
References[1] S. Geprägs et al. Nature Com. 7, 10452 (2016).
[2] P.G. Evans et al. Science Advances 2020, 6 (40), eaba9351. DOI: doi:10.1126/sciadv.aba9351.

51

Role of magneto-crystalline anisotropies in complex rare-earth garnets
Bruno Tomasello a, Danny Mannix b, Jack Thomas-Hunt c, Stephan Geprägs d,and Tim Ziman ead

University of Kent, Canterbury, UK.

b

ESS, Lund, Sweden.

Walther-Meissner-Institute, Garching, Germany.

ecAarhus University, Denmark.

Institute Laue-Langevin, Grenoble, France.

Author Email: brunotomasello83@gmail.com

Rare-earth crystals offer a rich variety of fascinating phenomena, such as emergent gauge
theories, topological phases, magnetoelasticity, multiferroicity, and unconventional ordering.
Complex garnet crystals combining transition-metal (TM; e.g. Fe) and rare-earth (RE; e.g. Tb)
ions are considered among the most intriguing ones because of the intertwined physics arisingfrom the open d- and f-shell electrons of TM and RE ions, respectively. The microscopic
mechanisms underpinning their magnetic and electric response are considered pivotal forharnessing energy-conversion in garnet-based spintronic devices, especially to move beyond
the yttrium iron garnet paradigm [1].
Motivated by the knowledge that crystal-fields anisotropies allowed for the description of themagnetostatics of individual ions and for the spin-dynamics of their effective lattices [2, 3], we
complement experiments on the structure and dynamics of rare-earth iron garnets – RE3Fe5O12– with theoretical studies whose building blocks exploit the wave-functions of the RE felectrons. Focussing on the challenges posed by terbium iron garnet – Tb3Fe5O12 – we discuss
the role of the electric and magnetic contributions to the multipoles of the RE ions, and weoverview the predictions permitted by the knowledge of the D2 point-group symmetry of a rareearth ion in a garnet [4]. In relation to experiments, we tackle the azimuthal dependence fromthe theory of resonant elastic x-ray scattering (REXS), detailing on the competing contributions
from the crystalline axes and the magnetic dipolar moments [5].

Figure 1: Local crystalline anisotropies (light blue arrow) of the simplest magnetic unit of Tb-ions(red spheres, c-sites) in a Tb-garnet – the triangle is the basic ‘simplex’ of the hyperkagome latticewhich host the RE-ions in garnet crystals. The blue and the green spheres, respectively d- and asites, show the TM ions nearest neighbours to the central RE-triangle from the unit-cell of a garnet.

References[1] S. Geprägs et al., Nature Communications, 7, 10452 (2016). doi:10.1038/ncomms10452[2] R. Wawrzyńczak et al., PRB 100, 094442 (2019). doi: 10.1103/PhysRevB.100.094442[3] B. Tomasello et al., Annals of Physics, p169117 (2022). doi:10.1016/j.aop.2022.169117[4] B. Tomasello et al. – Manuscript in preparation (2023).
[5] M.Blume, Resonant Anomalous X-ray Scattering, Theory and Applications, Elsevier Science, p. 495 (1994).

52

The Study on Water Repellent Behavior of Hydrophobic Coatings
by Soft X-ray Spectroscopy
Yusuke Tomiyoria,b, Hisao Kiuchia, Miho Kitamurac, Daisuke Asakurad,f, Eiji Hosonoe,f,Yoshihisa Haradaa,faInstitute for Solid State Physics, The University of Tokyo, b Innovative Technology Laboratories,
AGC Inc., c Institute for Advanced Synchrotron Light Source, National Institutes for Quantum Scienceand Technology (QST), d Research Institute for Energy Conservation, National Institute of Advanced
Industrial Science and Technology (AIST), e Global Zero Emission Research Center, National
Institute of Advanced Industrial Science and Technology (AIST), f AIST-UTokyo Advanced
Operando Measurement Technology Open Innovation Laboratory (Operando OIL), AIST.
E-mail: tomiyori.y@issp.u-tokyo.ac.jp
Self-assembled monolayers (SAMs) are nanostructures known for their ability to modify interfacial
properties of substrates such as metals and metal oxides, and provide useful functionality such as
biocompatibility [1]. Among them, SAMs containing fluorine are known to provide unique properties
such as high water repellency, slipperiness, and lubricity due to their low surface tension, and have been
extensively studied and developed in various industrial fields [2, 3]. Understanding the hydrophobicmechanism of materials at the molecular level is useful for the development of functional materials, butlittle is known about the influence of the chemical structure of SAMs on water adsorption behavior.
In this study, we employed soft X-ray emission spectroscopy (XES), a powerful tool for examining theoccupied electronic structure of light elements including water, to acquire a deeper understanding ofwater adsorption behavior on SAMs with different water repellency and chain structures.
We conducted XES measurements on hydrocarbon and fluorocarbon chain structures of SAMs withdifferent water repellency by using a setup developed by our research group that enables XES
measurements under precise humidity control (Fig. 1). The results in Fig. 2 demonstrated that watermolecules were progressively trapped on the surface and within the chain, as indicated by theenhancement of the 1b1' peak corresponding to trapped water with an increasing supply of watermolecules for the hydrocarbon chains, while no such behavior was observed in the fluorocarbon chains(Medium humidity). On the other hand, there was no significant change for both chains in the initialadsorption phase of water (Low humidity). Based on the results of XES and molecular dynamics
simulations, we discuss in detail the behavior of water adsorption on molecular chains with different
water repellency.

Fig. 1. Schematic of experimental setup for XES
measurements and magnified image of substrate surface.
References[1] Love J. C. et al., Chem. Rev., 2005, 105, 1103–1170.
[2] Sidharam P. P., et al., Langmuir, 2012, 28, 17690–17700.
[3] Shinoda, W., et al., Langmuir, 2019, 35, 14316−14323.

53

Fig. 2. O1s XES spectra obtained
during humid gas flowing over SAMs.

Cu L3-edge resonant inelastic x-ray scattering on
isostructural copper oxides CaCu3Fe4O12 and EuCu3Fe4O12
T. Yamaguchia, R.-P. Wangb, H.-Y. Huangc, A. Singhc, M. Gotod, Y. Takahashia, Y. Katoe,
D.-J. Huangc, J. Okamotoc, M.-J. Huangf, K. Kikuchia, H. Anzaia,
J. Kunešg, I. Yamadad, and A. HarikiaaDepartment of Physics and Electronics, Osaka Metropolitan University,1-1 Gakuen-cho, Nakaku,
Sakai, Osaka 599-8531, Japan, bDepartment of Physics, University of Hamburg, Laruper Chaussee
149, G610, 22761 Hamburg, Germany, cNational Synchrotron Radiation Research Center, No.101
Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan, dDepartment of Material Science andEngineering, Osaka Metropolitan University,1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531,
Japan, eDepartment of Material Science and Engineering, Osaka Prefecture University,1-1 Gakuencho, Nakaku, Sakai, Osaka 599-8531, Japan, fDeutsches Elektronen-Synchrotron DESY, Notkestraße85, 22607 Hamburg, Germany, gInstitute of Solid State Physics, TU Wien, 1040, Vienna, Austria
sa22908w@st.omu.ac.jp
We report a Cu L3-edge resonant inelastic
x-ray scattering (RIXS) study for theelectronic structure of isostructural copper
perovskite oxides CaCu3Fe4O12 (CCFO)
and EuCu3Fe4O12 (ECFO) with different
insulating and magnetic ground states:
CCFO is a ferromagnetic insulator and
ECFO is an antiferromagnetic insulator[1,2]. As shown in Figs.(a,c), the Cu L3-edge
RIXS map exhibits a strong material
dependence. The RIXS spectra are analyzed
using local density approximation (LDA) +dynamical mean-field theory (DMFT) [3]and a conventional CuO4 cluster model.

The experimental Cu L3-edge RIXS spectra for (a) CCFO and (c)ECFO. The LDA+DMFT Anderson impurity model spectra for (b)CCFO and (d) ECFO. White lines in panels are Cu L3-edge XAS
spectra for corresponding compounds. (e) The comparison of theexperimental and calculated spectra by the LDA+DMFT method
and CuO4 cluster model.

A low-energy excitation is observed at
ELoss~0.7eV in ECFO, that is absent in
CCFO, see Figs.(a,c,e). We identified thisfeature as a transition from the Zhang-Rice singlet ground state to a Zhang-Rice triplet excited state.
Besides, clear double peaks at ELoss~2eV, see Fig.(e), are observed in the dd excitations of ECFO, while
CCFO exhibits only a broad single-peak dd feature. The double peaks of ECFO originate from aninterplay of crystal-field and Hund’s excitations. Based on the experimental findings as well as acomparison of the LDA + DMFT and cluster-model simulations, we discuss the microscopic origin ofdifferent electronic properties in the two compounds.
References[1] Y. Shimakawa, J. Phys. D: Appl. Phys. 49, 119601 (2016).
[2] I. Yamada, J. Ceram. Soc. Jpn, 122, 846 (2014).
[3] A. Hariki et al., Phys. Rev. B, 101, 115130 (2020).

54

Anisotropic Magnetic Dipole Detectable by Resonant X-ray Scattering
Yuichi Yamasaki aaCenter for Basic Research on Materials, National Institute for Materials Science,
Tsukuba 305-0047, Japan
Author Email: YAMASAKI.Yuichi@nims.go.jp

Magnetic and electric dipoles are a source of magnetism and ferroelectricity, respectively. Electric
quadrupoles, described by electron multipoles, cause orbital ordering. Such fundamental degrees of
freedoms play important roles in phase transitions and various responses with broken symmetry.
Magnetic and electric multipoles are mainly discussed within single ion site. Recently, an augmented
magnetic multipole has been generalized as a cluster inter-atomic multipole. For example, a 120-degree
antiferromagnetic structure in Mn3Sn is regarded as a magnetic cluster composed of the same symmetry
as a magnetic octupole. The augmented magnetic octupole is related to an anisotropic magnetic dipole,
which can be detected by x-ray magnetic circular dichroism [2,3]. I will discuss a possibility ofanisotropic magnetic dipoles detectable by resonant x-ray scattering with some specific examples.
References
[1]
[2]
[3]

Satoru Hayami, Megumi Yatsushiro, Yuki Yanagi, and Hiroaki Kusunose, Phys. Rev. B 98, 165110 (2018)
Yuichi Yamasaki, Hironori Nakao , and Taka-hisa Arima, J. Phys. Soc. Jpn. 89, 083703 (2020)
M. Kimata, Y. Yamasaki et al., Nature Communications 12, 5582 (2021)

55

Hard X-ray High Energy Resolution Spectroscopy Beamline at HighEnergy Photon Source
Yujun Zhanga,b, Zhiying Guoa,b, Shuoxue Jina,b, Wei Xua,baHigh Energy Photon Source, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing,
100049, P.R. China, bBeijing Synchrotron Radiation Facility, Institute of High Energy Physics,
Chinese Academy of Sciences, Beijing, 100049, P.R. China
Author Email: zhangyujun@ihep.ac.cn

Since 2019, the 6-GeV green-field 4th generation (with emittance <60 pm·rad) synchrotron facility,
High Energy Photon Source (HEPS), is being built in Beijing, China. [1-2] The Hard X-ray High Energy
Resolution Spectroscopy Beamline in HEPS Phase-I provides a suite of inelastic x-ray scattering
spectroscopies using hard X-rays of 7~26 keV, such as nuclear resonant scattering, x-ray Raman
scattering (XRS) and (non-)resonant inelastic x-ray scattering (IXS) spectroscopies. [3-4] For IXS, a 4
m-wide and 3 m-high “Qiankun (乾坤)” spectrometer is designed (Figure 1). A RIXS module withswitchable 1 m/2 m Rowland circles as well as the rest XRS modules can be installed on the spectrometer,
sharing the same granite base, KB mirror and sample stages. Specifically, the RIXS module and highenergy resolution monochromators enable RIXS experiments with tunable energy resolution in theenergy range of 7~15 keV. Once completed, the new spectrometer of the new beamline at the new
synchrotron source will serve users for a variety of applications spanning over condensed matter physics,
chemical/material sciences, etc. In this presentation, we will show the progresses of the beamline as well
as related scientific perspectives.

Figure 1. “Qiankun (乾坤)” spectrometer with RIXS module installed.

References[1] Y. Tao, Groundbreaking Ceremony at the High Energy Photon Source in Beijing. Synchrotron Radiation
News 32, 40-40 (2019).
[2] Y. Jiao, G. Xu, X.-H. Cui, Z. Duan, Y.-Y. Guo, P. He, D.-H. Ji, J.-Y. Li, X.-Y. Li, C. Meng, Y.-M. Peng, S.K. Tian, J.-Q. Wang, N. Wang, Y.-Y. Wei, H.-S. Xu, F. Yan, C.-H. Yu, Y.-L. Zhao and Q. Qin, The HEPS
project, Journal of Synchrotron Radiation, 25, 1611-1618. (2018)[3] http://english.ihep.cas.cn/heps/doc/3552.html[4] W. Xu, Nuclear resonant scattering program in China: opportunities and challenges at the High Energy
Photon Source in Huairou. Möss. Eff. Ref. Data J. 40, 213-218 (2017).

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Momentum-resolved RIXS studies on high-temperature superconductor
Bi2212J. S. Sua,b, H. Y. Huangb, J. Okamotob, C. T. Chenb, T. Watanabec, C. Y. Moud, T. K. Leee,g, A.
Fujimorib,d,f, D. J. Huanga,b,g
aDepartment of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan,bNational Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, cGraduate School of
Science and Technology, Hirosaki, Aomori 036-8561, Japan, dCenter for Quantum Technology andDepartment of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan, eInstitude of Physics,
Academia Sinica, Taipei 11529, Taiwan, fDepartment of Physics, University of Tokyo, Bunkyo-ku,
Tokyo 113-0033, Japan, gDepartment of Physics, National Tsing Hua University, Hsinchu 30013,
TaiwanAuthor Email: htel880628.ep06@nctu.edu.tw
We used momentum-resolved measurements of Cu L3-edge resonant inelastic x-ray scattering (RIXS)
to investigate the charge excitations of optimally-doped Bi2Sr2CaCu2O8+δ (Bi2212). Our
momentum-resolved RIXS data are in agreement with the calculated charge susceptibility. The
observed charge excitation in the 2D momentum plane indicates the presence of long-ranged Coulombinteraction between valence electrons. However, the scattering pattern notably differs from thering-like feature reported in prior RIXS measurements. In addition, the RIXS spectral weight of charge
excitation changes across Tc, providing experimental evidence of the superconducting gap. Our results
confirm that RIXS can probe the evolution of charge gap across the superconducting phase transition.