Poster Session

-Poster SessionThe poster number with "S" is eligible for the Best Student Poster Award nomination.

P01

Research and Development of Magnet for HiSOR-II
Y. Lua, M. Shimadac,a , H. Miyauchic,a, M. Katoha,ba Hiroshima Synchrotron Radiation Center, Hiroshima University, HSRC, Japanb Institute for Molecular Science, Okazaki, IMS, Japanc High Energy Accelerator Research Organization, KEK, Japan

P02S

Experimental Study on Single Electron Storage
Y. Asaia, H. Miyauchib, c, M. Shimadab, c, M. Katohb, d

a Graduate School of Advanced Science and Engineering Hiroshima University, Japanb Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, Japanc High Energy Accelerator Research Organization (KEK), Japand UVSOR Synchrotron Facility, Japan

P03

Diffraction of Optical Vortex from Undulator
Y. Nishiharaa, M. Shimadac,b, H. Miyauchic,b, K. Matsuob,a, M. Katohb,a,da School of Science, Hiroshima University,, Japanb Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, Japanc High Energy Accelerator Research Organization (KEK), Japand UVSOR Synchrotron Facility, Japan

P04S

Unexpected two-fold symmetry of the electronic structure in heavily
overdoped Bi2201 observed by angle-resolved photoemission spectroscopy
Y. Miyaia, S. Idetab, T. Kurosawac, M. Odad, K. Tanakae, M. Aritab
K. Shimadaba Graduate School of Advanced Science and Engineering, Hiroshima University, Japanｂ Hiroshima Synchrotron Radiation Center, Hiroshima University, Japanc Faculty of Science and Engineering, Muroran Institute of Technology, Japand Department of Physics, Hokkaido University, Japane UVSOR-III Synchrotron, Institute for Molecular Science,Japan

P05S

Comprehensive Studies of the Electronic Structure for the Double-layer
high-Tc Superconductor Bi2Sr2CaCu2O8+ δ- Revisit of the Phase Diagram by ARPES
Y. Tsubotaa, Y. Miyaib, S. Kumarb,c , K. Tanakad, S. Ishidae, H. Eisakie,
S. Nakagawaf, T. Kashiwagif, M. Aritab, K. Shimada a,b, S. Idetaa,ba Graduate School of Advanced Science and Engineering, Hiroshima Univ., Japanｂ Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima Univ., Japanc Institute of Microelectronics (IME), Agency for Science, Technology and Research(A* STAR), Singapore
d UVSOR-Ⅲ Synchrotron, Institute for Molecular Science, Japane National Institute of Advanced Industrial Science and Technology (AIST), Japanf Division of Materials Science, Tsukuba University, Japan

-Poster SessionThe poster number with "S" is eligible for the Best Student Poster Award nomination.

P06S

Probing the Electronic Band Structure of Altermagnetic
MnTe: An ARPES Study
K. G. Martuzaa, Y. Kumara, S. Kumarb,c, S. Idetaa,b K. Shimadaa,ba Graduate School of Advanced Science and Engineering, Hiroshima University, Japanb Hiroshima Synchrotron Radiation Centre (HiSOR), Hiroshima University, Japanc Institute of Microelectronics, Agency for Science, Technology and Research (A*STAR),
Singapore

P07S

Effects of Quantum Charge Fluctuations on the Electron Self-energy ofHigh–Tc Cuprate Superconductors Using Angle-Resolved Photoemission
and Inverse Photoemission Spectroscopies
Y. Onishia, Y. Miyaia, Y. Tsubotaa, K. Tanakac, S. Ishidad, H. Eisakid,
H. Satob, M. Aritab, K. Shimadaa,b, S. Idetaa,ba Graduate School of Advanced Science and Engineering, Hiroshima Univ., Japanb Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima Univ., Japanc UVSOR-Ⅲ Synchrotron, Institute for Molecular Science, Japand National Institute of Advanced Industrial Science and Technology (AIST), Japan

P08S

Observation of Topological Surface States and Non-symmorphic Band
Degeneracy in Superconducting PdSeTe Single-crystal
Y. Kumara, S. Kumarb, Y. Venkateswarad, R. Oishia, J. Nayakc, T. Onimarua,
S. Idetaa,b, K. Shimadaa,ba Graduate School of Advanced Science and Engineering, Hiroshima University, Japanb Hiroshima Synchrotron Radiation Centre (HiSOR), Hiroshima University, Japanc Department of Physics, Indian Institute of Technology, Indiad Department of Physics, SUNY Buffalo State University, USA

P09S

Strain-Induced Relocation of Topological Surface States in Bi2Se3 Single
CrystalY. Kumara, S. Kumarb, S. Idetaa,b, T. Okudaa,b, K. Shimadaa,ba Graduate School of Advanced Science and Engineering, Hiroshima University, Japanb Hiroshima Synchrotron Radiation Centre (HiSOR), Hiroshima University, Japan

P10S

Research of Charge Fluctuations in the Electron-doped High-Tc Cuprate
NCCO Revealed by ARPES and IPES
H. Yamaguchia, Y. Onishib, Y. Miyaib, Y. Tsubotab, M. Atirac, K. Tanakad,
H. Satoc, D. Songe, K. Shimadab,c, S. Idetab,ca School of Science, Hiroshima Univ., Japanb Graduate School of Advanced Science and Engineering, Hiroshima Univ., Japanc Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima Univ., Japand UVSOR-Ⅲ Synchrotron, Institute for Molecular Science, Japane Stewart Blusson Quantum Matter Institute, University of British Columbia, Canada

-Poster SessionThe poster number with "S" is eligible for the Best Student Poster Award nomination.

P11

XPS study on the boron-doped amorphous carbon films
Y. Muraokaa, K. Matusob, T. Wakitaa, T. Yokoyaa

a AResearch Institute for Interdisciplinary Science, Okayama University, Japanb Graduate School of Natural Science and Technology, Okayama University, Japan

P12

Synchrotron ARPES studies of nodal line semimetal LaTe1+xBi1-x
R. Saitoa, Y. Okishia, T. Higashikawaa, T. Wakitaa,b, Y. Kumarc, Y. Miyaic,
H. Kageyamaa, R. Kondoa, Y. Nogamia, S. Idetac, K. Shimadac, Y. Muraokaa,b,
T. Yokoyaa,ba Graduate School of Natural Science and Technology, Okayama University,, Japanb Research Institute for Interdisciplinary Science, Okayama University, Japanc Hiroshima Synchrotron Radiation Center, Hiroshima University, Japan

P13

Current Activities of Research and Education on BL-5 (FY2023)
T. Yokoyaa,b, T. Wakitaa, Y. Muraokaa,ba Research Institute for Interdisciplinary Science, Okayama University, Japanb Research Laboratory for Surface Science, Okayama University, Japan

P14

Visualization of boron distributions in cancer cells dosed with a borondelivery drug
T Wakitaa, K. Igawab, M. Kanedac, N. Ikedac, H. Teratod, Y. Muraokaa,c,T. Yokoyaa,ca Research Institute for Interdisciplinary Science, Okayama University, Japanb INeutron Therapy Research Center, Okayama University, Japanc Graduate School of Natural Science and Technology, Okayama University, Japand Advanced Science Research Center, Okayama University, Japan

P15S

Fermi surface of chiral magnet Yb(Ni1-xCux)3Al9 observed by ARPES
Y. Tanimotoa, M. Sugimotoa, R. Kamimoria, Y. Nakashimab, H. Satoc,
K. Yamagamid, M. Aritac, S. Kumarc, K. Shimadac, S. Nakamurae, S. Oharae
a Graduate School of Advanced Science and Engineering, Hiroshima University, Japanb Faculty of Science, Hiroshima University, Japanc Hiroshima Synchrotron Radiation Center, Hiroshima University, Japand Japan Synchrotron Radiation Research Institute, Japane Graduate School of Engineering, Nagoya Institute of Technology, Japan

P16

ARPES study of TiFexS2 (x = 0, 0.33)
Y. Nakashimaa, Y. Tanimotob, M. Sugimotob, H. Satoc, Y. Miyaib, S. Idetac,
K. Shimadac, M. Miyatad, M. Koyanod

a Faculty of Science, Hiroshima University, Japanb Graduate School of Advanced Science and Engineering, Hiroshima University, Japanc Hiroshima Synchrotron Radiation Center, Hiroshima University, Japand School of Materials Science, Japan Advanced Institute of Science and Technology, Japan

P17S

Preparation of Pt Thin Film on MgO (001) and Observation of Its Electronic
Structure
T. Asanoa, K. Sumidab, K. Kunitomoa, T. Okudab, K. Miyamotob

a Graduate School of Advanced Science and Engineering, Hiroshima University, Japanb Hiroshima Synchrotron radiation Center (HSRC), Hiroshima University, Japan

-Poster SessionThe poster number with "S" is eligible for the Best Student Poster Award nomination.

P18S

Attempt to Control the Anisotropy of Topological Surface States
R. Yamamotoa, K. Sumidab, K. Miyamotob, T. Okudaba Graduate School of Advanced Science and Engineering Hiroshima University, Japanb Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, Japan

P19S

Spin-polarized electronic states of FeCo thin film on Rh(001) substrate
K. Kunitomoa, K. Sumidab, K. Miyamotob, C. Zhanga, Y. Sakurabac, T. Okudaba Graduate School of Advanced Science and Engineering Hiroshima University, Japanb Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, Japanc National Institute for Materials Science (NIMS), Japan

P20

Ultrafast Spin-Dependent Dynamics in a Carrier-Tuned Topological Insulator
K. Sumidaa, K. Kunitomob, M. Kakokib, K. A. Kokhc, O. E. Tereshchenkoc,
J. Reimannd, J. Güdded, U. Höferd, K. Miyamotoa, T. Okudaa,e, A. Kimurab,ea Hiroshima Synchrotron Radiation Center, Hiroshima University, Japanb Graduate School of Advanced Science and Engineering, Hiroshima University, Japanc Physics Department, Novosibirsk State University, Russia
d Department of Physics and Materials Sciences Center, Philipps-University, Germany
e International Institute for Sustainability with Knotted Chiral Meta Matter (SKCM2), Japan

P21S

Demonstration of phase-resolved spin-ARPES on topological surface states
in Bi2Te3
T. Kousaa, T. Iwataa,b, S. Kumarc, A. Kimuraa,b, K. Miyamotoc, T. Okudab,cK. Kurodaa,ba Graduate School of Advanced Science and Engineering, Hiroshima University, Japanb International Institute for Sustainability with Knotted Chiral Meta Matter(WPI-SKCM2),
Hiroshima University, Japanc Hiroshima Synchrotoron Radiation Center, Hiroshima University, Japan

P22S

Performance of laser-based SARPES with micrometer spatial and vector
spin resolution at HiSOR
T. Iwataa,b, T. Kousaa, A Y. Nishiokaa, K. Ohwadaa, K. Sumidac, E. Annesed,
M. Kakokia, K. Kurodaa,b, H. Iwasawae, M. Aritac, S. Kumarc, A. Kimuraa,b,
K. Miyamotoc, T. Okudab,ca Grad. Sch. Adv. Sci. Eng., Hiroshima Univ., Japanb WPI-SKCM¬2., Hiroshima Univ., Japanc HiSOR, Hiroshima Univ., Japand Brazilian Center for Research in Physics, Brazil
e Institute for Advanced Synchrotron Light Source, National Institutes for Quantum Scienceand Technology, Japan

P23

Direct Observation of Spin-split Electronic Structures in Antiferromagnet
NdBi by Laser-based SARPES
R. Yamamotoa, T. Motoyamab, T. Iwataa,b, T. Kosab, Y. Nishiokab, K. Ideurab,
M. Aritac, S. Idetac, K. Shimadaa,c, K. Miyamotoc, T. Okudaa,c, A. Kimuraa,b,T. Onimarub, K. Kurodaa,ba International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM2),
Hiroshima University, Japanb Graduate School of Advanced Science and Engineering, Hiroshima University, Japanc Hiroshima Synchrotron Radiation Center, Hiroshima University, Japan

-Poster SessionThe poster number with "S" is eligible for the Best Student Poster Award nomination.

P24

Secondary Structural Changes of FUS-LC induced with Phase-Separation
observed by VUV-CD
K. Fujiia, N. Maitaa, K. Matsuob, M. Katoaa Institute for Quantum Life Science, National Institutes for Quantum Science and Technology,Japanb Hiroshima Synchrotron Radiation Center, Hiroshima-university, Japan

P25

Insights into Physical Interactions and Structuration in Self-Assembled
Azapeptide Hydrogels Through Spectroscopy Techniques
M. Ibrahima,b, J. Bodiguelb, M. Averlant-Petitb, K. Matsuoa

a Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima University, Japanb Université de Lorraine, CNRS, LCPM, France

P26S

Monitoring the Self-Assembly of Alginate Hydrogel Using Synchrotron Radiation
Circular Dichroism
T. Hagaa, M. Yoshidaa, T. Hainoa, K. Matsuob, M. I.A. Ibrahimb

a Graduate School of Advanced Science and Engineering, Hiroshima University, Japanb Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima University, Japan

P27S

VUVCD Measurements of dried proteins and its application to proteinmembrane interaction study
K. Hayashia, R. Imauraa, K. Matsuoa,ba Graduate School of Advanced Science and Engineering, Hiroshima University, Japanb Hiroshima Synchrotron Radiation Center, Hiroshima University, Japan

P28

Optical Activity Measurement of Circularly Polarized Lyman-α Light
Irradiated and Magnetic Field Applied Amino-acid Films
J. Takahashia, M. Kobayashib, G. Fujimoric, H. Otad, K. Matsuoe, Y. Tairad,
M. Katohd,e, K. Kobayashic,f, Y. Kebukawaf, H. Nakamuraba Doshisha University, Japanb National Institute for Fusion Science, Japanc Yokohama National University, Japand UVSOR Synchrotron Facility, Japane Hiroshima Synchrotron Radiation Center, Japanf Tokyo Institute of Technology, Japan

P29S

Molecular orientation in polymer/fullerene blend films studied by NEXAFS
Y. Hanakia, H. Yoshidab,c, T. Sekitanib,ca Faculty of Science, Hiroshima University, Japanb Graduate School of Advanced Science and Engineering, Hiroshima University, Japanc Hiroshima Synchrotron Radiation Center, Hiroshima University, Japan

-Poster SessionThe poster number with "S" is eligible for the Best Student Poster Award nomination.

P30S

Charge Transfer in Gold Substrates and Nanoparticles Coated with Methyl
Ester Substituted Aromatic Thiol Molecules
S. Tendoa, A. Niozua, K. Yoshiokaa, J. Adachib, H. Tanakab, S. Wadaa,ba Graduate School of Science and Engineering, Hiroshima University, Japanb Photon Factory, Institute of Materials Structure Science, KEK, Japanc Hiroshima Synchrotron Radiation Center, Hiroshima University, Japan

P31

Ultrafast charge transfer through biphenyl and fluorene monolayers studied
by core-hole clock spectroscopy
A. Niozua, K. Yoshiokaa, S. Tendoa, S. Asakurab, Y. Hanakib, J. Koizumib,
Y. Ohurab, J. Yamadab, S. Wadaa, c
a Graduate School of Science and Engineering, Hiroshima University, Japanb Faculty of Science, Hiroshima University, Japanc Hiroshima Synchrotron Radiation Center, Hiroshima University, Japan

P32

Soft X-ray Absorption Spectroscopy of Phospholipid Films Supported on Au
Substrates by Different Casting Techniques
Y. Ohuraa, K. Yoshiokab, S. Tendob, A. Niozua,b, S. Wadaa,b,c

a Faculty of Science, Hiroshima University, Japanb Graduate School of Science and Engineering, Hiroshima University, Japanc Hiroshima Synchrotron Radiation Center, Hiroshima University, Japan

P01

光源

Research and Development of Magnet for HiSOR-II
Y. Lua, M. Shimadac,a , H. Miyauchic,a, and M. Katoha,baHiroshima Synchrotron Radiation Center, Hiroshima University, HSRC, Higashi-Hiroshima,
Hiroshima 739-0046, Japanb
Institute for Molecular Science, Okazaki, IMS, Aichi 444‑8585, Japanc
High Energy Accelerator Research Organization, KEK, Tsukuba, Ibaraki 305-0801, Japan

Keywords: Combined-function magnet, Hybrid permanent magnet, Energy saving

HiSOR-II has been designed as a future plan of HSRC, which will provide higher brightness VUVradiation increasing by 2 orders of magnitude compared with the present HiSOR. To reduce the construction
cost and accelerator size, the magnets in the ring lattice are being designed as combined-function magnets
which are capable of producing multipole field components, such as dipole, quadrupole, and sextupole. On
the basis of lattice parameters of HiSOR-II, we proposed two kinds of combined-function quadrupolesextupole magnets using auxiliary coil and pole profile adjustment, respectively [1, 2]. The magnet model issimulated using Radia [3], which is shown in Figure 1. In the combined-function magnet using auxiliary coil,the magnet pole profile is designed from a quadrupole magnet, and the sextupole magnetic field is generated
by a sextupole coil on the pole face and a dipole correction coil around the pole. The quadrupole magnetic
field and sextupole magnetic field can be adjusted separately. However, the structure is complicated andrequires three independent power sources. As for the magnet using pole profile adjustment, the pole profile
is a superimposition of the quadrupole and sextupole equipotential surfaces, which represents that thequadrupole and sextupole fields are adjusted in the design stage and fixed. Therefore, it is not compatible
with flexible optics that changes in the operation.

FIGURE 1. Combined-function quadrupole-sextupole magnets (a) with using auxiliary coil and (b) with pole profile
adjustment.

To reduce the operation cost, we are also considering using an electrical/permanent hybrid magnet forenergy saving [4]. The magnetomotive force is mainly generated by the permanent magnet material. The coilis assembled to provide part of magnetomotive force and adjust magnetic field strength. Such a kind ofmagnet can save the costs for electrical power. In addition, the magnet can get rid of water-cooling systemof the coil because of a low current density. However, permanent magnets are difficult to achieve highprecision and easy adjustability of the field strengths. Furthermore, there are other issues such as temperaturedependence and demagnetization caused by radiation. We also found that the existence of the PM in themagnetic circuit produces a large magnetic resistance against the magnetomotive force produced by the coil.
To solve this issue, we continue careful design study on the magnet configuration.
In order to apply the hybrid permanent magnet to HiSOR-II, the thermal effect compensation is being
studied by using a permanent dipole magnet developed at Nagoya University [5]. In the experiment, it isobserved that the variation of the dipole field strength is almost proportional to the temperature of thePermanent Magnet (PM), as shown in Figure 2.
1.

1 .

1.

1

1.

1 .

1.
1
1.
1 .

1.

1

1.

ts

1.

1

12.

2

y

empera re of the M

FIGURE 2. Variation of the By and temperature of the PM when current density is 2A/mm2.

A feedback control system for the magnetic field correction were tested. The drift of magnetic field isless than 0.0002 T (0.014%). In the future, the performance of the feedback system will be improved byincreasing the precision of the measurement of the magnetic field and temperature.

REFERENCES
1.
2.
3.
4.
5.

M. Katoh et al, "Upgrade plan for UVSOR," in Proc. of the 2th Asian. Part. Accel. Conf, Beijing, China, 2001.
W. Beeckman, et al, in Proc. PAC2013, Pasadena, CA USA, pp. 1229-1231.
http://www.esrf.eu/Accelerators/Groups/InsertionDevices/Software/Radia
G. Tosin, et al, Nuclear Instruments and Methods in Physics Research A 674 (2012) 67–73.
S. Fukue, et al, in Proc. of the 13th annual meeting of PASJ, August 2016, Chiba, Japan.

P02S##(A or B)(G or U)### (HiSOR proposal number)BL-## (HiSOR beamline number)

Experimental Study on Single Electron Storage
Y. Asaia, H. Miyauchib, c, M. Shimadab, c and M. Katohb, daGraduate School of Advanced Science and Engineering Hiroshima University, 1-3-1 Kagamiyama
Higashi-Hiroshima 739-8526, Japanb
Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University 2-313 Kagamiyama
Higashi-Hiroshima 739-0046
cHigh Energy Accelerator Research Organization (KEK), 1-1 Oho Tsukuba 305-0801, JapandUVSOR Synchrotron Facility, 38 Nishigo-Naka Myodaiji Okazaki 444-8585, Japan

Keywords: electron, photon, undulator, synchrotron radiation, quantum mechanics

We have started single electron storage experiments at UVSOR since 2021 with the aim of conducting
fundamental research on electromagnetic radiation. At BL1U, we extracted undulator light in the UV region
at a wavelength of 355 nm into the atmosphere and observed its intensity by a photomultiplier tube, as
reducing background light using appropriate band-pass filters, and decreased the electron beam intensity
using a beam scraper. We succeeded in observing a step-function-like intensity change under a small numberof electron storage conditions with a good SN ratio and in confirming the single electron storage. In 2022,
we improved the method of observing the accumulation state of single electron and attempted to observe
undulator radiation from single electron.
This study utilizes an insertion device called a tandem undulator, which consists of two undulators
arranged in series. It is known that the synchrotron radiation from the tandem undulator shows a finely
modulated spectrum with the envelope of that from one undulator, as shown in Fig. 1 [1]. This modulationis the result of the spectral interference between the radiation from two undulators.

FIGURE 1. Spectra at a low beam current Ib = 0.1 mA; (a) from single undulator and (b) from tandem undulator.

The number of photons emitted during single passage of an electron in the undulator is much less thanunity, which is in the same order of fine structure constant. Then, we have a question that when the single
electron radiate single photon in the tandem undulator, does the spectrum shows the modulation? This issimilar to Young’s interference experiment but in the time domain. We have conducted such an experimentat UVSOR BL1U. The latest result from the experiment will be presented at the symposium.

REFERENCES
1. M. Billardon et al., J. Phys. Colloques 44, 1983, pp. 29-71

P03

Diffraction of Optical Vortex from Undulator
Yu Nishiharaa, Miho Shimadac,b, Hiroshi Miyauchic,b, Koichi Matsuob,a,Masahiro Katohb,a,daSchool of Science, Hiroshima University, 1-3-1 Kagamiyama Higashi-Hiroshima 739-8526, Japanb
Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University 2-313 Kagamiyama
Higashi-Hiroshima 739-0046
cHigh Energy Accelerator Research Organization (KEK), 1-1 Oho Tsukuba 305-0801, JapandUVSOR Synchrotron Facility, 38 Nishigo-Naka Myodaiji Okazaki 444-8585, Japan

Keywords: Undulator, Synchrotron radiation, Optical vortex, Diffraction.

It has been theoretically shown that radiation from an electron in circular motion with a relativistic speed
has vortex property. Electron motion in a helical undulator radiation may be regarded as combination of
mildly relativistic circular motion and ultra-relativistic drift motion along the rotation axis which is identicalwith the undulator axis. Therefore, helical undulator radiation has vortex property such that the fundamental
component is circularly polarized plane wave and the higher harmonics are circularly polarized but opticalvortex with helical wavefront. When we apply undulator vortex radiation to some experiments, it is desirable
to observe the helicity and the topological charge of the vortex beam at various position in the beam-line. It
is well known that optical vortex shows interesting diffraction patterns for various apertures. We can get
information on the vortex property from the diffraction patterns. Among these, diffraction from triangularaperture seemed most feasible for our purpose.
To make a systematic study on the triangular diffraction, we have prepared triangular aperture of several
size. The experiment was carried out at BL1U of UVSOR-III storage ring. This beam-line equipped with
APPLE-II type undulator. By setting it in the helical mode with the fundamental wavelength at 710nm, thesecond harmonic radiation at 355 nm was extracted to the air. By using conventional CCD Camera, we madeobservation on the diffraction pattern. Some of the results are shown in Figure 1. We succeeded in observing
the characteristic pattern which shows the helicity and the topological charge. Some more details on theexperimental results will be presented in the symposium.

FIGURE 1. Diffraction by triangular aperture of helical undulator radiation observed at UVSOR BL1U, for 1st harmonic(left) and 2nd harmonic radiation (center and right, the helicity is reversed). The wavelength is centered at 355nm.

P04S

20AU018, 22AG005, 22BG004

BL-9A

Unexpected two-fold symmetry of the electronic structurein heavily overdoped Bi2201 observed by angle-resolved
photoemission spectroscopy
Y. Miyaia, S. Idetab, T. Kurosawac, M. Odad, K. Tanakae, M. Aritab
and K. ShimadabaGraduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 7398526, Japanb
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-8526, Japanc
Faculty of Science and Engineering, Muroran Institute of Technology, Muroran 050-8585, Japand
Department of Physics, Hokkaido University, Sapporo 060-0809, JapaneUVSOR-III Synchrotron, Institute for Molecular Science, Okazaki 444-8585, Japan

Keywords: High-TC superconductor, ARPESHigh transition-temperature (TC) cuprate superconductors have attracted much interest since theirdiscovery in 1986 for their high TC as well as unusual physical properties such as a pseudogap [1] and a
Nematicity [2]. Superconductivity occurs in the CuO2 plane and the Cu 3dx2−y2 state forms the Fermi surface(FS). It has been widely believed that the CuO2 plane is four-fold symmetric so far. Recently, however,symmetry reduction of the electronic structure has been reported in Bi-based cuprate superconductors [2,3].
Note that the breaking of the four-fold rotational symmetry or nematicity has been also found in theelectronic structure of iron-based superconductors [4]. Although the nematicity in electron liquid has
attracted much interest, the rotational symmetry breaking in the electronic structure of high-TC cuprate
superconductors has not been directly clarified yet.
In this study, we examined the symmetry of the electronic structure of the cuprate superconductors
using high-resolution angle-resolved photoemission spectroscopy (ARPES). Here, as a suitable system forthis study, we have selected heavily overdoped Bi-based high-Tc cuprates, (Bi,Pb)2Sr2CuO6+δ (Pb-Bi2201)
because it has a single CuO2 plane in the unit cell and the superstructure reflections are suppressed by Pb
doping. Furthermore, the pseudogap disappears in the heavily overdoped sample and one can clearly see theentire FS in the normal state.
By mechanically rotating the sample, we found the difference of nodal distances for the two nodal
directions (#1 and #2 in the inset of Fig. 1(a)) at the Fermi level (𝐸𝐸F ). The two-fold symmetry was obvious
if we compared the observed FS with the four-fold symmetric theoretical FS given by the tight-binding
model. In addition, the ARPES spectral intensities at the 𝐸𝐸F were different for these two nodal directions.
To further examine many-body interactions, we have evaluated self-energies (Σ (#1) , Σ (#2) ) as shown in Figs.
1(a) and 1(b) along the two nodal directions #1 and #2 in the inset of Fig. 1(a). Since the experimentally
extracted real and imaginary parts of the self-energies satisfy the Kramers-Kronig relation, the two-foldanisotropy should be intrinsic, indicating that the many-body interactions such as the electron-electron andthe electron-boson (phonon) interactions are anisotropic in these two nodal directions. Note that theobserved symmetry breaking of the electronic structure is independent of temperature in the range usedin this study (20 – 260 K).
The two-fold symmetry of the electronic structures in the heavily overdoped Pb-Bi2201 may berelated to a charge order formation in heavily overdoped Pb-Bi2201 as observed by resonant inelastic X-ray
scattering [5]. Our results provide an insight for the intriguing physical properties such as the nematicity [2]and the ferromagnetic fluctuation [6] of the heavily overdoped Bi2201.

FIGURE 1. (a), (b) Experimentally obtained self-energy (Σ) along the orthogonal two nodal directions. Red and blue dots
indicate Σ(#1) and Σ(#2) extracted from #1 and #2 directions as shown in the inset of panel (a) respectively.
1.
2.
3.
4.
5.
6.

M. Hashimoto et al., Nature Physics 10, 483 (2014).
S. Nakata et al., npj Quantum Materials 6, 86 (2021).
N. Auvray et al., Nature Communications 10, 5209 (2019).
H. C. Xu et al., Physical Review Letters 117, 157003 (2016).
Y. Y. Peng et al., Nature Materials 17, 697 (2018).
K. Kurashima et al., Physical Review Letters 121, 057002 (2018).

P05S

22BG004, 23BG012

BL-9A

Comprehensive Studies of the Electronic Structure for the
Double-layer high-Tc Superconductor Bi2Sr2CaCu2O8+δ
- Revisit of the Phase Diagram by ARPES
Y. Tsubotaa, Y. Miyaib, S. Kumarb,c, K. Tanakad, S. Ishidae, H. Eisakie,
S. Nakagawaf, T. Kashiwagif, M. Aritab, K. Shimada a,b, and S. Idetaa,ba Graduate School of Advanced Science and Engineering, Hiroshima Univ., Higashi-Hiroshima 739-0046, Japanb Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima Univ., Higashi-Hiroshima 739-0046, Japan, Agency for Science, Technology and Research (A*STAR),
Singapore 138632, Singapore
dUVSOR-Ⅲ Synchrotron, Institute for Molecular Science, Okazaki, Aichi 444-8585, JapaneNational Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8560, JapanfDivision of Materials Science, Tsukuba University, Tsukuba, Ibaraki 305-8577, Japan
cInstitute of Microelectronics (IME)

Keywords: high-Tc cuprate superconductors, ARPES, electronic structure, strongly correlated electron materials

It has been known that the cuprate superconductors show a high superconducting (SC) transition
temperature (Tc) and exotic physical properties. However, the SC mechanism of cuprates has been unclear
yet. In order to understand the mechanism of the microscopic origin of the high-Tc cuprate, various
theoretical and experimental studies have been done so far [1]. In high-Tc cuprate superconductors,
superconductivity occurs by hole doping into the CuO2 plane. The superconducting transition temperature
Tc as a function of hole concentration was reported as schematically shown in Fig. 1 [2]. For the hole-doped
cuprate superconductors, it has been widely believed that the phase diagram is universal, and the highest Tc
occurs at the hole concentration of ~0.16. However, recent angle-resolved photoemission spectroscopy(ARPES) experiments indicated that the empirical phase diagram may not be universal and shifted toward
the overdoped region [3-5].
In this study, we have performed ARPES measurements systematically to directly investigate theelectronic structure of the underdoped, optimally doped, and overdoped regions with three different
compositions of the double-layer cuprate, Bi2Sr2CaCu2O8+ (Bi2212). We have estimated the holeconcentration of each sample from the Fermi-surface area and compared them quantitatively. Fig. 1 shows
the Fermi surface of the optimally doped Bi2212 with Tc = 92 K and determined the Fermi momentum (reddots in Fig. 1) from the ARPES lineshape analyses.
In this poster presentation, we will show the results of the hole concentration estimated from the Fermi
surfaces in Bi2212 for each sample and are compared with the previous study to understand the relationshipbetween the hole concentration and Tc, namely, the new phase diagram. In this study, we found that the phase
diagram differs from the reported one [2]; the maximum Tc shifts toward the overdoped region. Furthermore,
we have measured the electronic structure in which the pseudogap closes and verified its consistency withrespect to the carrier concentration below and above Tc. Based on the present ARPES study, we will show
the new phase diagram in Bi2212 and discuss the results in comparison with other studies [6,7].

FIGURE 1. Schematic phase diagram reported from Ref. [2] (left). Fermi surfaces of Bi2212 observed by ARPES (right).
Red dots indicate the Fermi momentum estimated from the momentum-distribution curves near the Fermi level. White curves
are the Fermi surfaces fitted by tight-binding model. The bonding and antibonding bands are shown by the white curves,
respectively.

REFERENCES
1.
2.
3.
4.
5.
6.
7.

B. Keimer et al., Nature 518, 179-186 (2015).
J. L. Tallon et al., Phys. Rev. B 51, 12911(1995).
H. Sakamoto et al., J. Phys. Soc. Jpn. 85, 104710(2016).
I. K. Drozdov et al., Nat. Commun. 9, 5210(2018).
R. Sobota et al., J. Phys. Soc. Jpn. 88, 064711(2019).
I. M. Vishik et al., Proc. Nat. Acd. Sci. 109 (45), 182-18337 (2012).
S-D. Chen, et al., Science 366, 1099–1102 (2019).

P06S

23BG012

BL-9A

Probing the Electronic Band Structure of Altermagnetic
MnTe: An ARPES Study
Kazi Golam Martuzaa, Yogendra Kumara, Shiv Kumarb,c, Shin-ichiro Idetaa,b and
Kenya Shimadaa,baGraduate School of Advanced Science and Engineering, Hiroshima University, Japan 739-0046b
Hiroshima Synchrotron Radiation Centre (HiSOR), Hiroshima University, Japan 739-0046
cInstitute of Microelectronics, Agency for Science, Technology and Research (A*STAR), Singapore
Keywords: MnTe, altermagnet, electronic structure, ARPES

Altermagnetism is a recently recognized type of magnetism with vanishing net magnetization and atime-reversal symmetry broken electronic structure and have attracted much interest for their distinct
magnetic characteristics and prospective applications [1]. As a canonical altermagnetic material, MnTe hasgarnered a lot of interest recently [2-6]. MnTe with a hexagonal NiAs-type structure is one of the few
semiconductors among the 3d transition-metal compounds [3,4].
In this study, we investigated the electronic band structure of the hexagonal MnTe (0001) bulk single
crystal using polarization dependent angle-resolved photoemission spectroscopy (ARPES). The samples
were prepared by mixing stoichiometric amounts of finely powdered Mn and Te and sealed in evacuatedquartz ampoule at 10-5 pa. We grew MnTe single crystal by solid reaction method and cut it to exhibit the(0001) plane. For getting clean surface we sputtered and annealed the sample. We used 2kV beam energy
for sputtering and annealing temperature was 330 degree Celsius. By repeated cycles of sputtering andannealing, we could finally get a clean surface. The impurity of the surface was checked by the Auger
electron spectroscopy and the long-range order was confirmed by the sharp hexagonal low-energy electron
diffraction (LEED) spots. The polarization dependent ARPES experiments were done on HiSOR BL-9A
equipped with an ASTRAIOS electron analyzer. We set the photon energy at 40 eV and the temperature at
200K. The polarization direction of the incident light was controlled by the undulator magnets configuration.
Figs. 1(a) and 1(b) show the kx-ky ARPES intensity map at the chemical potential taken with the sand p-polarization geometries, respectively. Although MnTe is a semiconductor, due to the intrinsic hole
doping, the chemical potential is located below the top of the valence band. The photoemission intensity ismuch intense taken at the s-polarization geometry indicating that the electron wave functions are odd withrespect to the mirror plane. It indicates the observed valence bands are derived from Mn 3𝑑𝑥𝑦 , Mn 3𝑑𝑦𝑧 ,and Te 5𝑝𝑦 states. The spectral intensity is strong around the Γ̅ point and the ARPES intensity map along̅̅̅̅ direction in Fig. 1(c) suggests an existence of hole-like bands, which is consistent with the bandthe ΓKstructure calculations [5,7]. The ARPES intensity mapping at the chemical potential in Fig. 1(a) is compatible
with the hexagonal (0001) surface.
̅
K

(a)

(b)

̅




̅
K

(c)

̅
K

̅




̅
K

(d)

FIGURE 1. High-resolution ARPES results on MnTe (0001) single crystal taken at 200K and h=40 eV. kx-

ky mapping at the chemical potential with the s-polarization (a) and p-polarization (b) geometries. ARPES
̅̅̅̅ high symmetry line with the s-polarization (c) and p-polarization (d) geometries.
intensity map along the ΓK

REFERENCES[1] S. Lee et al., Phys. Rev. Lett. 132, 036702 (2024).
[2] S. Mu et al., Phys Rev Mater. 3, 025403 (2019).
[3] De Melo et al., Journal of Crystal Growth 110, 445-451 (1991).
[4] H. Sato et al., Journal of Magnetism and Magnetic Materials 140-144, 153-154 (1995).
[5] P. E. Faria Junior et al, Phys. Rev. B 107, L100417 (2023).
[6] T. Osumi et al., http://arxiv.org/abs/2308.10117.
[7] S. J. Youn et al., Physica Status Solidi (B) 241, 1411–1414 (2004).

P07S

23BG012, 23BU010

BL-9A, IPES

Effects of Quantum Charge Fluctuations on the Electron
Self-energy of High–Tc Cuprate Superconductors Using
Angle-Resolved Photoemission and Inverse Photoemission
Spectroscopies
Y. Onishia, Y. Miyaia, Y. Tsubotaa, K. Tanakac, S. Ishidad, H. Eisakid,
H. Satob, M. Aritab, K. Shimadaa,b, and S. Idetaa,ba Graduate School of Advanced Science and Engineering, Hiroshima Univ., Higashi-Hiroshima 739-0046, Japanb Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima Univ., Higashi-Hiroshima 739-0046, Japanc UVSOR-Ⅲ

Synchrotron, Institute for Molecular Science, Okazaki, Aichi 444-8585, Japand National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8560, Japan

Keywords: high- Tc superconductors, ARPES, IPES, charge fluctuations, electronic structure

In the previous studies of angle-resolved photoemission spectroscopy (ARPES), it has been reported thatkink structures are observed in the electronic structure for the cuprates likely due to spin fluctuations and/or
phonons [1-3]. This observation indicates that the glue of the Cooper pair is magnons or phonons. On theother hand, in recent years, resonant inelastic x-ray scattering experiments have been performed in the holeand electron-doped high-Tc cuprate superconductors and charge excitations are observed [4 ,5]. In addition,
theoretical calculations of unconventional high-Tc superconductors using the layered t-J model, which
includes the long- and short-range Coulomb interactions with charge fluctuations, have been reported to
study how charge fluctuations interact to the electronic structure in cuprates [6, 7]. However, the effect ofcharge fluctuations to the electronic structure of cuprates has not been studied by angle-resolved
photoemission spectroscopy (ARPES) directly.
In this study, to investigate the role of charge fluctuations for the electronic structure in the high-Tc cuprate
superconductor, Bi2Sr1.6La0.4CuO6+δ (Bi2201), we have performed ARPES and inverse photoemission
spectroscopy (IPES) to study the occupied and unoccupied states, respectively. In the experiments, ARPES
and IPES measurements are performed along high-symmetry lines in the Brillouin zone (Fig. 1, (a)). We
found the shoulder structure near 1 eV above the Fermi level in the IPES spectra as shown by red area in
Fig. 1 (b). In the poster presentation, we will show the details of the electronic structure on Bi2201 in theoccupied and unoccupied states and discuss the effect of charge fluctuations on the electronic structure ofhigh-Tc cuprate superconductors, including a comparison with theoretical calculations [6, 7].

(b)
(a)

FIGURE 1. (a) The Fermi-surface on the Brillouin zone for Bi2201. Each arrow corresponds to the arrow in the panel (b). (b)Energy-distribution curves in the second Brillouin zone (T = 13K, Ekin = 50eV).

REFERENCES
1. A. Lanzara et al., Nature 412, 510 (2001).
2. P. V. Bogdanov et al., Phys. Rev. Lett. 85, 2581 (2000).
3. S. M. Hayden et al., Nature 429, 531–534 (2004).
4. K. Ishii et al., Phys. Rev. B 96, 115148 (2017).
5. A. Singh et al., Phys. Rev. B. 123, 235105 (2022).
6. H. Yamase et al., Phys. Rev. B 104, 045141 (2021).
7. H. Yamase et al., Commun Phys 6, 168 (2023).

P08S
22AG001, 22AU002

BL-1 (HiSOR)

Observation of Topological Surface States and Nonsymmorphic Band Degeneracy in Superconducting
PdSeTe Single-crystal
Y. Kumara, S. Kumarb, Y. Venkateswarad, R. Oishia, J. Nayakc, T. Onimarua,
S. Idetaa,b, K. Shimadaa,baGraduate School of Advanced Science and Engineering, Hiroshima University, Japan 739-0046
bHiroshima Synchrotron Radiation Centre (HiSOR), Hiroshima University, Japan 739-0046
cDepartment of Physics, Indian Institute of Technology, Kanpur, India 208016
dDepartment of Physics, SUNY Buffalo State University, New York, USA 14222

Keywords: Weyl semimetal, superconductivity, ARPES study, DFT calculation

Topological semimetals with topologically non-trivial band structures have been the focus of recent
theoretical and experimental studies [1-3]. Dirac semimetals (DSMs), Weyl semimetals (WSMs), andtopological nodal-line semimetals are the three main sub-categories of topological semimetals, which can becharacterized according to the form and degeneracy of the band crossings near the Fermi level [4]. The
layered transition metal chalcogenides among the DSMs and WSMs are particularly significant for theirvarious intriguing physical properties, such as superconductivity and charge density wave (CDW) withapplication potentials [5].
In this study, we have successfully synthesized high-quality single crystals of PdSeTe which is acandidate of DSM by a two-step melting method and investigated the electronic band structure as well as
the superconducting properties. We performed angle-resolved photoemission spectroscopy (ARPES) of
PdSeTe on the beamline HiSOR BL-1. We have done the density functional theory (DFT) calculations andfound that PdSeTe hosts four-fold degenerate Dirac crossings at the A point, originating from the nonsymmorphic symmetry. These band crossings form a Dirac line node along the 𝛤 − 𝐴 direction, which islocated near the Fermi level and shows almost no energy dispersion. Therefore, Dirac fermions in PdSeTe
can be studied using transport measurements. To verify the surface contribution in the ARPES results, wehave done ℎ𝑣-dependent measurements and directly confirmed the presence of surface states in PdSeTe. The
observed surface-derived states match well with the DFT calculation for the slab model.

(a)

(b)

(c)

(d)
EF
0.25 eV
0.50 eV
0.75 eV

1.00 eV
1.25 eV

1.50 eV̅ − Г̅ − M
̅ direction with 25eV photon energy at 20K and
Fig. 1: (a) and (b) represent the measured ARPES spectrum along M
simulated bands for slab (5 atomic layers) respectively. (c) The Fermi surface and constant-energy contours of the ARPES
spectra at different binding energies. (d) The shows the experimental k z -dispersion along Г − A deduced from the hv ̅ − Г̅ − M
̅ direction.
dependent data measured along the M

REFERENCES
1. M.Z. Hasan, C.L. Kane, Reviews of Modern Physics 82, 3045-3067 (2010).
2. X.-L. Qi, S.-C. Zhang, Reviews of Modern Physics 83, 1057-1110 (2011).
3. Y. Xia et al., Nature Physics 5, 398-402 (2009).

4. B. Yan, C. Felser, Annual Review of Condensed Matter Physics 8, 337-354 (2017).
5. K. Kim, et al., PRB 97, 165102 (2018).

P09S

22AU002

BL-1 (HiSOR)

Strain-Induced Relocation of Topological Surface States in
Bi2Se3 Single Crystal
Y. Kumara, S. Kumarb, S. Idetaa,b, T. Okudaa,b, K. Shimadaa,baGraduate School of Advanced Science and Engineering, Hiroshima University, Japan 739-0046
bHiroshima Synchrotron Radiation Centre (HiSOR), Hiroshima University, Japan 739-0046

Keywords: Topological Insulator, in-situ Strain, ARPES, Dirac point, Straintronics.

To investigate the impact of strain on the surface and bulk electronic states of solids, we havedeveloped a new sample holder for in-situ strain application for ARPES experiments at low temperatures. In
this study, we report the design of the sample holder and ARPES results of a strain-induced modification of
the surface and bulk states of Bi2Se3 single crystal. Our findings reveal significant alterations in the electronic
band structure [6] (in terms of energy and momentum) of the Bi2Se3 layered topological insulator [1-4] whensubjected to tensile strain. Specifically, tensile strain leads to a closer proximity of the Dirac point (DP) tothe Fermi level (lower binding energy), while compressive strain results in the DP moving further away fromthe Fermi level (higher binding energy). This study demonstrates the tunability of both surface and bulk
electronic states in Bi2Se3 through the in-situ application of strain and underscores the potential of strainengineering for “Straintronics” [5] devices. The sample holder developed for this purpose holds promise foradvancing research on the electronic band structures of layered materials, including topological insulatorsand quantum materials [6-8], under strain conditions.
No Strain

TS_1R

TS_2R

RNP

TS_3R

̅ for Bi2Se3 single crystal with increasing tensile strain (TS) from TS_1R, to TS_2R,
FIGURE 1. ARPES maps along Г̅ − 𝐾
to TS_3R measured at 10 K with 25 eV photon energy. The DP moves to the lower energy. The DP position was not recovered
to the original position though we remove the tensile strain (RNP).
TABLE 1. Changes in fermi velocity, bottom of conduction band and shift in dirac point with respact to applied starin.
Change in parameters

𝑵𝒐 𝑺𝒕𝒓𝒂𝒊𝒏

𝑻𝑺_𝟏𝑹

𝑻𝑺_𝟐𝑹

𝑻𝑺_𝟑𝑹

𝑹𝑵𝑷

𝒌𝑭 (Å−𝟏 )0.08480.08460.08760.10370.1080𝑩𝒐𝒕𝒕𝒐𝒎 𝒐𝒇 𝒄𝒐𝒏𝒅𝒖𝒄𝒕𝒊𝒐𝒏 𝒃𝒂𝒏𝒅 (𝒆𝑽)−0.1555−0.1605−0.1655−0.1806−0.1856

𝑫𝒊𝒓𝒂𝒄 𝑷𝒐𝒊𝒏𝒕 (𝒆𝑽)−0.3398−0.3520−0.3584−0.3729−0.3862

REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.

L. Fu, C.L. Kane, E.J. Mele, Topological Insulators in Three Dimensions, Physical Review Letters 98 (2007) 106803.
L. Fu, C.L. Kane, Topological insulators with inversion symmetry, Physical Review B 76 (2007) 045302.
M.Z. Hasan, C.L. Kane, Colloquium: Topological insulators, Reviews of Modern Physics 82 (2010) 3045-3067.
Y. Ando, Topological Insulator Materials, Journal of the Physical Society of Japan 82 (2013) 102001.
A.A. Bukharaev, A.K. Zvezdin, A.P. Pyatakov, Y.K. Fetisov, Straintronics: a new trend in micro- and nanoelectronics
and materials science, Physics-Uspekhi 61 (2018) 1175.
S. Riccò, M. Kim, A. Tamai, S. McKeown Walker, F.Y. Bruno, I. Cucchi, E. Cappelli, C. Besnard, T.K. Kim, P.
Dudin, M. Hoesch, M.J. Gutmann, A. Georges, R.S. Perry, F. Baumberger, In situ strain tuning of the metal-insulatortransition of Ca2RuO4 in angle-resolved photoemission experiments, Nature Communications 9 (2018).
I. Kostylev, S. Yonezawa, Z. Wang, Y. Ando, Y. Maeno, Uniaxial-strain control of nematic superconductivity in
SrxBi2Se3, Nature Communications 11 (2020) 4152.
E. Gati, L. Xiang, S.L. Bud'Ko, P.C. Canfield, Hydrostatic and Uniaxial Pressure Tuning of Iron‐Based
Superconductors: Insights into Superconductivity, Magnetism, Nematicity, and Collapsed Tetragonal Transitions,Annalen der Physik 532 (2020) 2000248.

P10S

22BG004, 23BU010

BL-1, IPES

Research of Charge Fluctuations in the Electron-doped
High-Tc Cuprate NCCO Revealed by ARPES and IPES
H. Yamaguchia, Y. Onishib, Y. Miyaib, Y. Tsubotab, M. Atirac, K. Tanakad,
H. Satoc, D. Songe, K. Shimadab,c, S. Idetab,cba School of Science, Hiroshima Univ., Higashi-Hiroshima 739-0046, Japan
Graduate School of Advanced Science and Engineering, Hiroshima Univ., Higashi-Hiroshima 739-0046, Japanc Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima Univ., Higashi-Hiroshima 739-0046, JapandUVSOR-Ⅲ Synchrotron, Institute for Molecular Science., Okazaki, Aichi 444-8585, Japane

Stewart Blusson Quantum Matter Institute,University of British Columbia,Vancouver, BCV 6T1Z4,Canada

Keywords: cuprate superconductors, charge fluctuation, electronic structure, ARPES, IPES

The origin of the high-Tc superconductivity has been extensively studied so far, but the bosonic interaction
to form electron pairs is still elusive. There are three degrees of freedom in the solid; orbital, charge, andspin [1]. According to the previous experimental reports [2-8], the promising candidates of the bosonicinteractions are phonons and magnons. On the other hand, the role of the charge fluctuation in the high-Tc
superconductivity is not well understood.
Recently, inelastic X-ray scattering experiments reported that charge excitations for both hole- and electrondoped cuprate high-Tc superconductors [9-11], and therefore, the effect of the charge fluctuation to the highTc superconductivity has attracted interest. According to the theoretical study [12], using the layered t-J
model, the electron self-energy is calculated and discussed about the effect of charge fluctuation in the
spectral function.
We have performed an ARPES and inverse photoemission spectroscopy (IPES) to observe the electronic
structure in the occupied and unoccupied states, respectively, on Nd1-xCaxCuO4 (x = 0.15) as shown in Fig.
1. We find that a strong peak structure exists in the energy region between 5 and 9 eV above the Fermi level(EF). In the poster presentation, we will show the details about the experimental data and discuss the effectfrom the charge fluctuation.

FIGURE 1. Experimental data observed by ARPES and IPES. Energy-distribution curves observed by IPES in the
direction of (0, 0)-(, ) is shown on the left side. On the right side, IPES spectra without the second derivative (above EF)
and the second-derivative intensity plot observed by ARPES (below EF) is shown.

REFERENCES
1. H. Hwang et al., Nat. Mater. 11, 103-113 (2012).
2. A. Lanzara et al., Nature 412, 510 (2001).
3. J. P. Carbotte et al., Nature 401, 354 (1999).
4. H. F. Fong et al., Phys. Rev. Lett. 75, 316 (1995).
5. L. Braicovich et al., PhysRevLett. 104, 077002 (2010).
6. M. Le Tacon et al., Nature Phys 7, 725-730 (2011).
7. J. Schlappa et al., Nature 485, 82-85 (2012).
8. M. P. M. Dean et al., Nature materials 12,1019-1023 (2013).
9. J. Lin et al., npj Quantum Mater. 5, 4 (2020).
10. A. Singh et al., Phys. Rev. B 105, 235105 (2022).
11. W. S. Lee et al., Nature Phys 10, 883-889 (2014).
12. H. Yamase et al., Phys. Rev. B, 104, 045141 (2021).

P11

BL-5

XPS study on the boron-doped amorphous carbon films
Yuji Muraokaa, Kota Matusob, Takanori Wakitaa and Takayoshi YokoyaaaResearch Institute for Interdisciplinary Science, Okayama University,
3-1-1 Tsushima-naka, Tsushima, Kita-ku, Okayama 700-8530, Japanb
Graduate School of Natural Science and Technology, Okayama University,
3-1-1 Tsushima-naka, Tsushima, Kita-ku, Okayama 700-8530, Japan
Keywords: XPS, Boron dope, Amorphous carbon, Film

Heavily boron (B)-doped amorphous carbon, which is called as B-doped Q-carbon, shows thesuperconductivity with a superconducting transition temperature of 55K [1,2]. Since B-doped Q carbon is
the first example of amorphous semiconductor showing the superconductivity, much efforts have been
devoted to preparing this material. However, preparation of this material is quite difficult because of its
metastable form achieved by the nano-second pulsed laser annealing to the B-doped amorphous carbon
precursors. So far, B-doped Q-carbon has not yet been reproduced. One of important studies related to the
preparation of B-doped Q-carbon is to characterize the B-doped amorphous carbon precursors. Especially,
the chemical states of B-doped amorphous carbon may affect the formation of the B-doped Q-carbon. In thisstudy, we investigate the chemical states of carbon and boron atoms in the B-doped amorphous carbon
precursors with different nominal boron content by means of an X-ray photoemission spectroscopy.
The B-doped amorphous carbon precursors were fabricated by a pulsed laser deposition method with a
KrF excimer laser (  = 248nm). Single crystal Al2O3(0001) substates were used for the film deposition. The
deposition was performed under the vacuum condition of 3.0 x 10-6 Pa. Nominal boron content in the films
was varied by changing the B/C ration in the target materials. The film thickness of the obtained precursor
films was 200 to 300 nm. X-ray photoemission spectroscopy (XPS) measurements were carried out on thebeamline BL-5, at the Hiroshima Synchrotron Radiation Center in Hiroshima University with nonmonochromatic Mg K X-ray source (h = 1253.6 eV). C 1s and B 1s core-level spectra were measured
under an ultrahigh vacuum of ~10-7 Pa using a VSW hemispherical analyzer. The total energy resolution was
about 1.8 eV. The binding energy of the films was corrected using the peak position of molybdenum spectra.
Before measurements, the films were annealed at 100 °C under ultrahigh vacuum (~10 -6 Pa) for 1 h toclean the film surface.
Figure 1 shows the C 1s core-level spectra of B-doped amorphous carbon films with different B content.
The peak at 285 eV is observed for the non-doped films. This peak position shifts toward lower binding
energy side with increasing boron content. Figure 2 shows the B 1s core-level spectra of B-doped amorphous
carbon films with different B content. The peak structure appears as the nominal boron content is increased,
indicating that boron atoms are present in the films. The B/C ratio of the films is estimated from the peakarea ratio of C 1s and B 1s spectra to be 0-0.27. The peak position is located at 189 eV, which originatesfrom B0 states [3]. This indicates that most of boron atoms exist as an elemental state in the films. The reason
for the shit of the C 1s spectra with increasing B content is probably due to the surface bending effect. It will
be interesting to see how the chemical states of carbon and boron atoms change after pulsed laser annealing.
Our present results provide an important starting point for obtaining the B-doped Q-carbon.

C 1s

B1s

B content

B/C

Intensity (a.u.)

Intensity (a.u.)

large

0.27
0.18

0.04

0
0
290

288

286

284

282

280

194

192

190

188

186

184

Binding Energy (eV)Binding Energy (eV)FIGURE 1. C 1s core-level spectra of

FIGURE 2. B 1s core-level spectra ofboron-doped amorphous carbon films
with different boron content.

boron-doped amorphous carbon films
with different boron content.

REFERENCES
1. A. Bhaumik, R. Sachan, and J. Narayan, ACS Nano. 11, 5351-5357 (2017).
2. A. Bhaumik, R. Sachan, S. Gupta, and J. Narayan, ACS Nano. 11, 11915-11922 (2017).
3. W. G. Shin, H. J. Jung, H. G. Sung, H. S. Hyun, and Y. Sohn, Ceram. Int. 40, 11511-11517 (2014).

P12

23BG016BL-1

Synchrotron ARPES studies of nodal line semimetal
LaTe1+xBi1-x
Ryusei Saitoa, Yuta Okishia, Tomoki Higashikawaa, Takanori Wakitaa,b ,Yogendra Kumarc, Yudai Miyaic, Haruka Kageyamaa, Ryusuke Kondoa,
Yoshio Nogamia, Shinichiro Idetac, Kenya Shimadac, Yuji Muraokaa,b,
Takayoshi Yokoyaa,baGraduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
bResearch Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan

cHiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan

Keywords: Topological material, Nodal line semimetal, Band dispersion, ARPES

LaTe1+xBi1-x is a layered material consisting of an insulating layer of LaTe and a conducting Bi squarelattice layer. Band calculation predicted that it possesses a Dirac nodal-line along -R in the Brillouin zone
(BZ) (Fig. 1) [1], and therefore it can be classified as a nodal line semimetal for which exotic transport
properties can be expected [2]. However, predicted nodal line of LaTeBi is located slightly above the Fermi
level (EF). To experimentally observe the nodal line and also determine its energy position relative to EF are
important to investigate the potential of LaTe1+xBi1-x to exhibit topological physical properties. In thispresentation, we report synchrotron angle-resolved photoemission spectroscopy (ARPES) study of
LaTe1+xBi1-x, which was performed to directly observe the valence band electronic structure of LaTe1+xBi1-x.
The samples measured were LaTe1+xBi1-x (x = 0.2) single crystals prepared by the flux method.
Synchrotron ARPES experiments were performed by a high-resolution ARPES spectrometer at BL-1 of
HiSOR, with linearly polarized light and with the light spot size of 40 (H) x 50 (V) µm. The energy resolution
was set to ~ 40 meV and the measurement temperature was 20 K.
Figure 1 shows an ARPES intensity map measured along the X line of the BZ. The black regions
correspond to bands. Distinct dispersive bands symmetric with respect to the high symmetry points areclearly observed in the entire energy region shown. The observed bands were found generally consistent
with the results of band calculations. Around X, one can find bands approaching EF.

FIGURE 1. ARPES intensity map of LaTe1.2Bi0.8 and Brillouin zoneFigure 2 shows a minus second-derivative ARPES intensity map near EF and around X. “W” shaped
dispersive bands symmetric with respect to X are observed. The characteristic dispersion is consistent withcalculation, indicating that a nodal line is located very close to EF at X in LaTe1.2Bi0.8.

FIGURE 2. Minus second-derivative ARPES intensity map near EF and around X of LaTe1.2Bi0.8

REFERENCES
1. R. Kondo, private communication.
2. C. Feng et al., Chinese Phys. B 25, 117106 (2016).

P13

23AG019

BL-5

Current Activities of Research and Education on BL-5
(FY2023)
T. Yokoyaa,b, T. Wakitaa and Y. Muraokaa,babResearch Institute for Interdisciplinary Science, Okayama University
Research Laboratory for Surface Science, Okayama University, Okayama 700-8530, Japan

Keywords: Photoemission spectroscopy, photoelectron emission microscopy

We present an overview of our resent research and educational activities on beamline 5 (BL5) in the fiscal
year 2023. Our beamline has two experimental stations in a tandem way. The first station is equipped withan angle-resolved photoemission spectrometer (ARPES), a low energy electron diffraction (LEED)
apparatus and an X-ray source. The hemispherical analyzer of ARPES spectrometer (HA54, VSW) has amean radius of 50 mm and is mounted on a twin axis goniometer in ultra-high vacuum chamber. Using thisgoniometer, one can perform ARPES and photoelectron diffraction (PED) measurements. It is also possible
to perform resonant photoemission spectroscopy (RPES) measurements by using photon energy tunabilityof synchrotron radiation with X-ray absorption spectroscopy (XAS) measurement. With the X-ray source(XR2E2, FISONS), we can perform an X-ray photoelectron spectroscopy (XPS) measurement for thechemical state analysis and the PED. At the second station, we have installed a photoelectron emission
microscope (PEEM, ‘PEEM III’, Elmitec). PEEM provides a magnified image of lateral intensity
distribution of photo-emitted electrons from a sample surface. The spatial resolutions are several ten
nanometers with Hg lamp and a few micrometers with synchrotron radiation. The sample is transferred
between the ARPES and the PEEM chamber in-situ, and one can perform measurements at both stations forthe same sample.
In the recent researches on BL-5, we have studied the electronic structure of potassium doped aromatic
molecule (Kx picene) [1], iron-based superconductor (FeSexTe1-x) [2], transition metal di-oxide films such as
VO2 thin films which exhibits a first-order metal-to-insulator transition at 340 K [3], CrO2 thin films which
are known as a half-metallic material [4], TaO2 film which is stabilized with a new technique developed inour group [5], and phase-separated TiO2-VO2 films on mica substrates. We have also studied the electronic
structures of a high-quality boron-doped diamond film which shows a signature of the highest
superconducting transition temperature of 25 K [6] and a high quality single crystal of YbFe2O4 which isone of multiferroic materials [7], by utilizing RPES at B K- and Fe M2,3- edges, respectively. In addition, we
have studied the sp3 content in diamond-like carbon films by using photoemission spectroscopy in order to
optimize the conditions to produce Q-carbon (quenched carbon) which is a newly discovered amorphous
phase of carbon with several exotic properties [8]. In the last few years, we have performed PEEM and TEY
measurements at BL5 in HiSOR for (1) a B-doped carbon nano wall film on a Si substrate, (2) a micro-droplet ofsolidified L-boronophenylalanine (L-BPA) on a Si substrate and (3) cancer cells dosed with L-BPA in order toinvestigate microscopic chemical states of trace B atoms in them from fine structures in local- and wide-areaXAS spectra near B K-edge and to visualize B distributions on their surfaces. For this kind of measurementswith PEEM, we have developed a new auto-measurement system where we can obtain a serial PEEM images
with excitation x-ray energies for a certain energy range with a fixed energy step.
Recently, we have prepared an auto-measurement system and an X-ray focusing capillary lens forphotoemission holography (PEH) measurements. PEH is a method that has been greatly developed in Japanin recent years as a measurement method for elucidating the local structure of materials with an atomic
resolution [9]. In particular, various results have been reported in the study of the three-dimensional atomic
configurational structure around the dopants in crystals [10]. However, the opportunity to use state-of-theart apparatuses (for example, DA30 analyzer and RFA of BL25SU at SPring-8) are limited. Although our
photoelectron energy analyzer is an old model and it is difficult to separate and observe small shifts in corelevels because of the energy resolution of 1-2 eV of the system, we expect that our apparatus will be used
for preliminary experiments on undoped materials prior to experiments for doped samples using state-of-the-art systems. It can also be used for educational purposes such as experiencing photoelectron holography
experiments and learning the analysis methods.
We have used the BL-5 for education activity as well, for example, practical education for undergraduate
students of Okayama University. The students have an opportunity to study the synchrotron radiation
mechanism and to experience XPS measurement which is very useful for the surface science research. We
accepted more than 100 students from 2006 to 2012. From 2014, we have started to join the practical lecture
for experiments using the beamline end stations in HiSOR for both graduate school students of Hiroshima
and Okayama Universities. In 2018, we have had a new project for education under a Japan-Asia youth
exchange program in science supported by Japan Science and Technology Agency (JST), “Sakura Exchange
Program in Science”. We have accepted six students from Changchun University of Science and Technology
in China.

REFERENCES
1. H. Okazaki et al., Phys. Rev 82, pp. 195114 (5 pages) (2010).
2. Y. Yoshida et al., J. Phys. Soc. Jpn 78, pp. 034708 (4 pages) (2009).
3. K. Saeki et al., Phys. Rev 80, pp. 125406 (5 pages) (2009).
4. Y. Muraoka et al., MRS Proceedings 1406 (2012).
5. Y. Muraoka et al., Thin Solid Films 599, pp. 125-132 (2016).
6. H. Okazaki et al., Appl. Phys. Lett 106, pp. 052601 (5 pages) (2015).
7. K. Fujiwara et al., Trans. Mater. Res. Soc. Jpn. 41, pp. 139-142 (2016).
8. H. Yoshinaka et al., Carbon.167, pp. 504-511 (2020).
9. T. Matsushita et al. Europhys. Lett. 71, 597 (2005). Phys. Status Solidi B 255, 1800091 (6 pages) (2018).
10. K. Hayashi, T. Matsushita, SPring-8 Research Frontiers 2020, pp. 12 -15 (2021).

P14

23AG019

BL-5

Visualization of boron distributions in cancer cells
dosed with a boron delivery drug
Takanori Wakitaa, Kazuyo Igawab, Miyu Kanedac, Naoshi Ikedac,
Hiroaki Teratod, Yuji Muraokaa,c, Takayoshi Yokoyaa,caResearch Institute for Interdisciplinary Science, Okayama Universityb
Neutron Therapy Research Center, Okayama UniversitycGraduate School of Natural Science and Technology, Okayama UniversitydAdvanced Science Research Center, Okayama University
Keywords: Photoemission electron microscopy, local X-ray absorption spectroscopy, elemental distributions

Boron Neutron Capture Therapy (BNCT) has attracted attention in recent years as a cancer treatment
method that aims to destroy only cancer cells without damaging normal cells. It has achieved remarkable
results in the treatments of cephalon and cervix cancers. [1]. In this method, cancer cells are destroyed by analpha-ray and a lithium ion emitted through a nuclear reaction between a boron nuclear and a thermal neutronray. In order to increase the probability of selectively destroying only cancer cells while causing as little
damage to normal cells as possible, it is essential to increase the accumulation of boron compounds on thetarget cancer cells, which will contribute to maximize the effect of BNCT with thermal neutrons of the lowest
possible intensity. Visualization of intracellular boron distribution using microscopic techniques provides
important clues for the development of boron compounds that can efficiently accumulate in cancer cells.
Electron probe micro analyzer (EPMA) has been widely used in visualization of microscopic elemental
distributions on various material surfaces as one of the most popular techniques, by means of combinationof a scanning electron microscope and an X-ray fluorescence analyzer [2]. X-ray fluorescence is produced
via relaxation of core-holes excited, in this case, by an electron beam, which is therefore element specific innature. For light elements such as boron (B), however, Auger transition rates are more than 99.9% in theircore-hole relaxation processes, which means that detection of trace light elements by X-ray fluorescence has
difficulty. In contrast, X-ray absorption spectroscopy (XAS) with total electron yield (TEY) is suitable todetect trace light elements because TEY is proportional to the amount of secondary electrons generated
mainly by Auger electrons [3]. The intensity of photoemission electron microscope (PEEM) is also
proportional to the TEY intensity when it is used with X-ray as a light source and without both an energy
filter and an energy analyzer [4]. One can obtain a local XAS spectrum by plotting intensities in a certain
area on a series of PEEM images as a function of X-ray energies. In addition, an elemental distribution image
can be obtained as a difference image of two PEEM images measured at X-ray energies of (1) a pre-edge
and (2) a peak position above a certain absorption edge.
In this study, we have performed PEEM and TEY measurements at BL5 in HiSOR for (1) a micro-droplet
of solidified L-boronophenylalanine (L-BPA), which is used as a boron delivery drug in clinical BNCTs, ona Si substrate and (2) cancer cells dosed with L-BPA, in order to investigate microscopic chemical states oftrace B atoms in them from fine structures in local- and wide-area-XAS spectra near B K-edge and tovisualize B distributions on their surfaces. For this kind of measurements with PEEM, we have developed a
new auto-measurement system where we can obtain a serial PEEM images with excitation x-ray energies
for a certain energy range with a fixed energy step. The experimental station of BL5 is equipped with a
PEEM III (Elmitec GmbH) and with a manipulator connected to a digital amperemeter for a TEY
measurement. As a light source, the second-order X-rays from the monochromator were used because they
have higher intensity and energy resolution around B K-edge than the first-order X-ray from themonochromator with the same entrance and exit slit widths. All the measurements were performed at room
temperature.
In order to elucidate the XAS signals from L-BPA, first we have performed PEEM and TEY measurements
for a micro-droplet of solidified L-BPA on a Si substrate. Figure 1 (a) shows an optical microscope image ofa micro-droplet on a Si substrate. The size of the micro-droplet is about 100 µm. Figure 1 (b) shows a PEEM
image of the same micro-droplet measured with Hg lamp showing 2 dimensional local work function
distribution for it. The field of view is 150 µm. The blue curve in figure 1 (c) shows plots of averaged
intensities per a pixel in blue square in figure 1 (b) as a function of X-ray energy around B K-edge, showing
a local XAS spectrum which has a sharp peak structure at 193.6 eV and a small bump at 191.6 eV. These
clear structures are not observed in an XAS spectrum measured by TEY (black curve in figure 1 (c)) which
provides an averaged information of the sample surface from a wide area illuminated by X-ray (the size of
X-ray is about 1 x 5 mm2 on the sample surface). These results demonstrate the effectiveness of PEEM
measurements for detecting signals from small amounts of substances on a sample surface.
Figure 2 (a) shows an optical microscope image of a colony of cancer cells dosed with L-BPA on a silicon
substrate. Figure 2 (b) shows a PEEM image of the same colony measured with X-ray of 195 eV. The fieldof view is 150 µm. The red curve in figure 2 (c) shows plots of averaged intensities per a pixel in red squarein figure 2 (b) as a function of X-ray energy around B K-edge. For the blue curve in figure 2 (c), 30 PEEM
images are summed for each X-ray energy, providing better S/N ratio of the blue curve than the one of the
red curve. The small structures in this local-XAS spectrum for the cancer cell does not resemble the ones infigure 1 (c) for micro-droplet of L-BPA. This suggests that the L-BPA may be decomposed in the cancer cell.
Further measurements to obtain more better S/N ratio in a local-XAS spectrum for the cancer cells are in
progress.

FIGURE 1. (a) An optical microscope image of a micro-droplet on a Si substrate. The size of the micro-droplet is about 100µm. (b) A PEEM image of the same micro-droplet measured with Hg lamp. The field of view is 150 µm. The blue curve in (c)shows plots of averaged intensities per a pixel in blue square in figure 1 (b) as a function of X-ray energy around B K-edge.
The black curve shows an XAS spectrum measured by TEY.

FIGURE 2. (a) An optical microscope image of a colony of cancer cells dosed with L-BPA on a silicon substrate. (b) A PEEM
image of the same colony measured with X-ray of 195 eV. The field of view is 150 µm. The red curve in (c) shows plots ofaveraged intensities per a pixel in red square in figure 2 (b) as a function of X-ray energy around B K-edge. For the blue

curve in figure 2 (c), 30 PEEM images are summed for each X-ray energy.

REFERENCES
1.
2.
3.
4.

H. Nakashima, YAKUGAKU ZASSHI 142, 155-164 (2022).
J. I. Goldstein et al., Scanning electron microscopy and X-ray microanalysis 4th ed., Springer (2017).
A. Erbil et al., Phys. Rev. B 37, 2450 (1988).
A. Locatelli and E. Bauer, J. Phys.: Condes. Matter 20, 093002 (2008).

P15S

HiSOR, BL-1, BL-9A / SPring-8, BL-25SU

Fermi surface of chiral magnet Yb(Ni1-xCux)3Al9
observed by ARPES
Y. Tanimotoa, M. Sugimotoa, R. Kamimoria, Y. Nakashimab, H. Satoc,
K. Yamagamid, M. Aritac, S. Kumarc, K. Shimadac, S. Nakamurae, S. OharaeaGraduate School of Advanced Science and Engineering, Hiroshima University,
Higashi-Hiroshima 739-8526, Japanb
Faculty of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japanc
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japand
Japan Synchrotron Radiation Research Institute, Sayo 679-5148, Japane
Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan
Keywords: chiral magnetic crystal, helical magnetism, angle resolved photoemission spectroscopy

Trigonal YbNi3Al9 has a chiral crystal structure belonging to space group of R32 (No. 155) and is ofinterest as the first chiral magnetic alloy discovered in 4f electron compounds [1]. The localized Yb 4f spinsare magnetically ordered below T=3.4 K, ferromagnetic in the c-plane, and exhibit left-handed or righthanded helimagnetism with propagation vector q=(0, 0, 0.8) [2]. Substitution of Ni with Cu significantly
alters the magnetic interaction and shortens the helical propagation vector to q=(0, 0, 0.4) forYb(Ni0.94Cu0.06)3Al9. Spin-polarized conduction electrons are thought to be responsible for this phenomenon.
In this study, we have performed vacuum ultraviolet and soft x-ray angle-resolved photoemission
spectroscopy (VUV-ARPES and SX-ARPES) on YbNi3Al9 and Yb(Ni0.94Cu0.06)3Al9 to observe the Fermi
surface. The experiments were carried out at BL-1 and BL-9A of Hiroshima Synchrotron Radiation Center(HSRC), Hiroshima University for VUV-ARPES and at BL-25SU of SPring-8 for SX-ARPES. Single
crystals used for the SX-ARPES measurements were synthesized by the flux-method [3].
VUV-ARPES revealed five hole-like Fermi surfaces around the Γ̅ points and an electronic Fermi surface̅ point for YbNi3Al9 and Yb(Ni0.94Cu0.06)3Al9. The Fermi surface of Yb(Ni0.94Cu0.06)3Al9 isaround the 𝐾
shrink compared to that of YbNi3Al9, although the feature is almost unchanged with the Cu substitution.
̅ directions of the surface
Figure 1(a) shows the SX-ARPES intensity plots of YbNi3Al9 along the Γ̅-𝑀
Brillouin zone measured at hv=548 eV with circular-polarized light. Figure 1(b) shows the angle integrated
spectrum. Two flat bands derived from the localized Yb2+ 4f7/2 states below the Fermi level (EF) and Yb2+
4f5/2 states at EB=1.4 eV are observed. Two hole-like bands around the Γ̅ point cross EF at kx=0.31 and 0.45
Å-1. These two hole-like bands are clearly observed in the VUV-ARPES spectra measured at hv=24 eV withs-polarized geometry.
Figure 2 represents the Fermi surface of YbNi3Al9 measured at hv=450~652 eV with circular- polarized
̅ direction of the surface
geometries. The horizontal and vertical axes are the wavenumbers kx along Γ̅-𝑀
Brillouin zone and kz along the Γ-Z direction of the bulk Brillouin zone, respectively. A barrel-shaped Fermi
surface the with the minimum kx at the Γ point and the maximum kx at the Z point is observed, as indicatedby a black line. Inside it, in addition, we find another barrel-shaped Fermi surface. On the other hand, theFermi surface observed around kx=0.15 Å-1(white line) appears to be a drum-shaped Fermi surface with theminimum kx at the Z point and is closed between the Γ and Z points as indicated by the arrows. These Fermi
surfaces are quantitatively consistent with the Fermi surfaces inferred from de Haas-van Alphen effect [4].

̅ direction measured at hv=548 eV with
Fig. 1 (a) SX-ARPES intensity plots of YbNi3Al9 measured along the Γ̅-𝑀
circular-polarized light. (b) Angle integrated spectrum of (a).

Fig. 2 Fermi surfaces of YbNi3Al9 obtained from SX-ARPES spectra measured at hv=450~652 eV with circularpolarized light.

REFERENCES
1. S. Ohara, S. Fukuta, K. Ohta, H. Kono, T. Yamashita, Y. Matsumoto and J. Yamaura, JPS Conf. Proc. 3, 017016 (2014).
2. T. Matsumura, Y. Kita, K. Kubo, Y. Yoshikawa, S. Michimura, T. Inami, Y. Kousaka, K. Inoue and S. Ohara, J. Phys.
Soc. Jpn. 86, 124702 (2017).
3. T. Yamashita, R. Miyazaki, Y. Aoki and S. Ohara, J. Phys. Soc. Jpn. 81, 034705 (2012).
4. S. Ohara, private communication.

P16

BL-7, BL-1

ARPES study of TiFexS2 (x = 0, 0.33)
Y. Nakashimaa, Y. Tanimotob, M. Sugimotob, H. Satoc, Y. Miyaib, S. Idetac,
K. Shimadac, M. Miyatad, M. KoyanodaFaculty of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
Graduate School of Advanced Science and Engineering, Hiroshima University,
Higashi-Hiroshima 739-8526, Japanc
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, JapandSchool of Materials Science, Japan Advanced Institute of Science and Technology, Nomi 923-1292, Japanb

Keywords: intercalation, superlattice, angle resolved photoemission spectroscopy

1T-TiS2 is non-magnetic layered material with 1T-CdI2-type crystal structure. The hexagonal layer of Ti
ions is sandwiched between the two hexagonal layers of S ions and the Ti ion is octahedrally coordinatedwith six S ions. The S-Ti-S triple layers are covalently bonded and these TiS2 triple layers are weakly coupledwith van der Waals (vdW) force. In the vdW gap located between the TiS2 layers, the other 3d transitionmetal M can be intercalated as MxTiS2. Among them, FexTiS2 exhibits a wide variety of magnetic properties[1]. With increasing the Fe concentration from x = 0, the cluster spin grass (CG) state with the Ising spins isfound for x < 0.20. After exhibiting the antiferromagnetic (AFM) state up from x = 0.20 to 0.28, the CG stateis again realized for 0.28 < x < 0.38 and the AFM state for 0.38 < x < 0.50. Above x = 0.50, the ferrimagnetic
behavior is observed. On the other hand, the Fe ion intercalated in the vdW gap between the TiS2 layers
occupy the octahedral site surrounded by six S ions. X-ray studies reveal the Fe random distribution for x <0.20, while the formation of 2Ö3a ´ 2a ´ 2c or 2a ´ 2a ´ 2c superlattices due to the Fe ordering for x = 0.25
and Ö3a ´ Ö3a ´ 2c superlattice for x = 0.33. The rich magnetic states of FexTiS2 are expected to link to thechange in electronic band structure due to the Fe intercalation. In this study, we carried out angle-resolved
photoemission spectroscopy (ARPES) to reveal the electronic band structure of FexTiS2 (x = 0, 0.33) atbeamlines BL-1 and BL-7 of Hiroshima Synchrotron Radiation Center (HSRC).
$ directions of
Figure 1(a) shows the ARPES intensity plots of TiS2 measured at hv=66 eV along the Γ"-Mthe surface Brillouin zone, roughly corresponding to G-M direction of the bulk Brillouin zone, estimatedfrom the hv-dependent measurements. We find an electron pocket derived from the Ti 3d states around the
M point. Almost non-dispersive band is observed at binding energy of EB = 0.3 eV, which is assigned to the
3d states of the Ti ions self-intercalated in the vdW gap between TiS2 layers. The parabolic band aroundthe G point is due to the S 3p states.

% direction.
FIGURE 1. ARPES intensity plots of (a) TiS2 and (b) Fe0.33TiS2 measured at hn = 66 eV along Γ#-M

Figure 1(b) shows the ARPES intensity plots of Fe0.33TiS2. The electron pocket around the M point isshifted to higher binding energy. In addition, the parabolic S 3p band is also shifted. These results indicatethat electrons are transferred from the intercalated Fe ions to host TiS2 layers. The dispersive Fe 3d-derived
band is observed around EB = 0.3 - 0.7 eV, reflecting the Fe ions align periodically in the vdW gap parallelto the TiS2 layers (in plane). The Fe 3d band seems to be bent upward before the M point, probably due tothe Ö3a ´ Ö3a periodicity in plane for x = 0.33. We measured the ARPES spectra along the G-A direction
with changing hv from 30 to 124 eV. We find that the Fe 3d band exhibits the dispersion along the direction
normal to the TiS2 layers and has half period of the S 3p band, reflecting the 2c periodicity due to theformation of Ö3a ´ Ö3a ´ 2c superlattice.

REFERENCES
1. N. V. Selezneva, E. M. Sherokalova, A. Podlesnyak, M. Frontzek and N. V. Baranov, Phys. Rev. Mater. 7, 014401 (2023).

P17S

23BG007

BL-7

Preparation of Pt Thin Film on MgO (001)and Observation of Its Electronic Structure
T. Asanoa, K. Sumidab, K. Kunitomoa, T. Okudab, and K. MiyamotobaGraduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama,
Higashi-Hiroshima 739-8526, Japanb
Hiroshima Synchrotron radiation Center (HSRC), Hiroshima University 2-313 Kagamiyama,
Higashi-Hiroshima 739-0046, Japan

Keywords: Pt thin film, Spin Hall effect, Photoemission spectroscopy

Spin Hall effect is an important physical phenomenon that generates spin-polarized currents and isessential for the development of spintronics devices. The spin Hall effect in metals has attracted attention
because conductance mismatches are markedly suppressed at an interface with ferromagnet compared to thesemiconductors and allows the use of spin-polarized current supplied by the ferromagnetic metal [1]. Among
many metals, elemental Pt is extensively investigated both experimentally and theoretically [2,3]. Kimura etal. reported that the Pt wire exhibits largest spin Hall conductivity as large as 2.4×104 S/m at room
temperature, which is 4 orders of magnitude larger than that of typical semiconductors, such as GaAs [2]. In
order to inject spin-polarized current into ferromagnets more efficiently, the orientation of spin current must
be precisely controlled, i.e., it is necessary to observe its spin orientation. In previous studies, the rough spinorientation of spin currents induced by spin Hall effects has been obtained by using the magneto-optical Kerr
effect [4]. However, the experimental method to precisely detect the spin orientation induced by the spin
Hall effect has not been established yet. One solution is operando spin-resolved photoemission spectroscopy(PES) measurements under an external electric field.
In this work, as a first step towards the development of the experimental method, we fabricated Pt thinfilms and investigated the electronic structure by PES measurements. The Pt thin films were prepared byusing electron beam evaporation source with a carbon crucible on a MgO(001) substrate at room temperature.
The MgO substrate was annealed in oxygen atmosphere (~10-1 Pa) at ~200℃ for 60 min., and then, annealed
at 600℃ for 240 min. in vacuum prior to the Pt deposition.
To observe the electronic structure of the fabricated Pt/MgO film, we performed the PES measurements
at BL-7 of Hiroshima Synchrotron Radiation Center utilizing various incident photon energies from 30 to
160 eV. Figure 1 shows Pt 4f core level spectrum taken at hν = 155 eV. Two peaks derived from the spinorbit split Pt 4f5/2 and 4f7/2 are clearly seen at binding energy (EB) of 74.4 and 71.1 eV. To obtain more detailed
information, the experimental result was fitted by Doniac-Šunjić function with Shirley background function[see blue curve in Fig. 1]. From this fitting result, asymmetric parameters were determined to be 0.018 for
4f5/2 and 0.043 for 4f7/2. These values are very small as a metal, suggesting that the density of states (DOS)near the Femi level (EF) is small.
The red curve in Fig. 2 shows the experimentally observed valence band PES spectrum taken at hν = 70
eV. We can see broad peak structures around EB = 1.6 and 4.5 eV. Moreover, a dip structure is recognized at
EB = 3.2 eV. To compare the valence band spectrum, we carried out the first-principles calculation for theface-centered-cubic Pt using WIEN2k program including the spin-orbit coupling. Based on the calculation,
it was found that the d orbital component is dominant in the valence band rather than the s and p orbitals.
Moreover, photo-onization cross-section of d orbital is dominated in the vacuum ultraviolet region.
Therefore, in Fig. 2, we compare the PES spectrum with the Pt d partial DOS. Here, the calculated Pt dpartial DOS was multiplied by the Fermi-Dirac distribution function at 300 K and convoluted by a Gaussianfunction (experimental resolution). Comparing the experimental and theoretical results, we notice that thelocations of the peak and dip structures and the band width are qualitatively reproduced. However, a very

sharp peak predicted by the calculation in the vicinity of EF was not observed in the experiment. This suggeststhat the interface and/or surface structure of the fabricated Pt film on MgO substrate makes the electronic
structure differ from the electronic structure in the bulk Pt.

FIGURE 1. Pt 4f core level spectrum (red circles) taken at hν = 155 eV. The blue curve represents the fitting
result using the Doniach-Šunjić function and active Shirley background (green curve).

FIGURE 2. Observed photoemission spectrum taken at hν = 70 eV (red) and the calculated Pt d partial DOS(blue). The calculated DOS is multiplied by the Fermi-Dirac distribution function and convoluted by aGaussian function.
In conclusion, we are successful to prepare Pt thin film on MgO(001) using electron beam evaporate
source with a carbon crucible. Around EF, the observed electronic structure on Pt thin film is differrent from
calculated spectrum based on the bulk Pt. In general, the performance of the spin Hall effect is closely related
to the electronic structure, so this finding of discrepancy may be important information for improving theperformance of the spin Hall effect for Pt thin film on MgO(001).

REFERENCES
1. G. Schmidt, et al, Phys. Rev. B 62, R4790(R) (2000).
2. T. Kimura et al., Phys. Rev. Lett. 98, 156601 (2007).
3. G. Y. Guo, et al., Phys. Rev. Lett 100, 096401(2008).
4. Y. K. Kato, et al, Science 306, 5703 (2004).

P18S

23AG036

BL-7

Attempt to Control the Anisotropy of Topological Surface
StatesR. Yamamotoa, K. Sumidab, K. Miyamotob, and T. Okudab.
aGraduate School of Advanced Science and Engineering Hiroshima University, 1-3-1 Kagamiyama
Higashi-Hiroshima 739-8526, Japanb
Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University 2-313 Kagamiyama,
Higashi-Hiroshima 739-0046, Japan

Keywords: Topological Surface States, Silicon Vicinal Surface, Anisotropy of Band Structure, Bi2Te3 film

Topological insulators have spin-polarized conduction states on their surfaces (= topological surface
states), where the spin direction of electrons is locked by their momentum resulting the helical spin-texture.
The unique helical spin-texture is considered to prohibit complete backscattering by non-magnetic impurities.
Thus, the surface of topological insulators is expected to be promising platform for spintronics devices.
However, other backscattering passes except for the complete backscattering are not prohibited [Fig.1(a)].
One solution to suppress the backscattering is forming an anisotropic Fermi surface, ideally a onedimensional Fermi surface[Figs. 1(b) and 1(c)].
In previous research, it has been reported that Ag films on Si(111)-(4×1)-In, which has an array of In
chains, exhibit a quasi-one-dimensional band structure [1]. This result is attributed to the confinement ofelectrons in the quasi-one-dimensional Ag films caused by the step and terrace structure, and a similar effectcan be expected even on vicinal surface. The vicinal silicon surface has atomically regular step arrays andelectron motion in the film grown on the surface might be restricted only one direction parallel to the step.
From this analogy, we considered that it might be possible to obtain the anisotropic spin-polarized band
structure by growing Bi2Te3 films on silicon vicinal surface. However, there is no report of the fabricationof Bi2Te3 film on silicon vicinal surface so far. Therefore, the purposes of this research are to fabricate Bi2Te3
film on silicon vicinal surface, measure the band structure, and evaluate the band anisotropy.
In our study, we grew Bi2Te3 ultrathin films on Si(111) and Si(557) by molecular beam epitaxy, whichwere used as flat and vicinal surface substrate, respectively. Si(557) is a surface tilted by 9.5° from Si(111),
and its terraces have the same plane as Si(111). We checked the quality of surface structure by low energy
electron diffraction (LEED) and auger electron spectroscopy (AES). Figure 2 shows LEED patterns and thespectra of AES of Bi2Te3 film on each substrate. As in Fig. 2, we can see clear spots in LEED and peak of
Bi and Te in AES indicating that we could succeed to grow Bi2Te3 film on vicinal silicon surface.
To observe the band structure of the fabricated films, angle-resolved photoemission spectroscopy(ARPES) measurements were done at BL-7 in HiSOR. Figure 3(a) shows the wide energy range ARPES
images on Si(111) (top) and Si(557) (bottom). Clear bulk bands are observed on Si(111). On Si(557) substratefaint but similar bands that are shifted by 9.5° from the results of Si(111) are observed. Figure 3(b) shows
the magnified band structure near the Fermi energy of each sample. A clear V-shaped topological surface
state is visualized on Si(111). The observed feature is very similar to the previously reported band structureof Bi2Te3/Si(111) films with one quintuple layer (QL) thickness [2]. Thus, the thickness of our film isestimated to be ~1 QL. On Si(557) substrate, similar V-shaped surface state crossing the Fermi energy canbe seen, but it was hard to estimate the Fermi momenta (𝑘 ) of surface bands due to the weak intensity.
Although we attempted to evaluate the anisotropy of the surface bands by Fermi surface in Fig. 3(c),unfortunately, it was also difficult.
In conclusion, we succeeded to grow Bi2Te3 film on silicon vicinal surface and to measure the band
structure. However it was difficult to evaluate the band isotropy because of the poor intensity of topologicalsurface states on Bi2Te3/Si(557). Further experiment with the better sample quality is expected in the future.

FIGURE 1. Schematic illustrations of isotropic (a), anisotropic (b), and ideally anisotropic (one-dimensional) Fermi
surfaces (c) of topological insulator.

FIGURE 2. (a) AES spectrum of Bi2Te3/Si(111) (b)LEED pattern of Bi2Te3/Si(111) taken at 55 eV. (c) AES spectrum of
Bi2Te3/Si(557) (d) LEED pattern of Bi2Te3/Si(557) taken at 39 eV.

FIGURE 3. (a) Wide range ARPES images of Bi2Te3/Si(111) and Bi2Te3/Si(557) acquired at hν = 35 and 70 eV. (b)Magnified ARPES images around the Fermi energy of (a). (c) Fermi surface of Bi2Te3/Si(111) and Bi2Te3/Si(557)

REFERENCES
1. N.Nagamura et al., Phys. Rev. Lett. 96, 256801 (2006).
2. S. Hatta et al., Sci. Rep. 11, 5742 (2021).

P19S

23AG037

BL-9B

Spin-polarized electronic states of FeCo thin film
on Rh(001) substrate
K. Kunitomoa, K. Sumidab, K. Miyamotob, C. Zhanga,
Y. Sakurabac, and T. OkudabaGraduate School of Advanced Science and Engineering Hiroshima University, 1-3-1 Kagamiyama,
Higashi-Hiroshima 739-8526, Japanb
Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University 2-313 Kagamiyama,
Higashi-Hiroshima 739-0046, Japanc
National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan

Keywords: FeCo alloys, spin polarization, perpendicular magnetic anisotropy (PMA)

The emergence of perpendicular magnetic anisotropy (PMA) in magnetic thin films is essential from theviewpoint of practical applications, e.g., increasing the recording density of storage devices. Many magnetic
thin films exhibiting PMA, such as Co/Pt, Co/Pd, FePt, TbFeCo, and GdFeCo, have been extensively
investigated. Among them, “rare-earth and noble-metal elements free” FeCo alloy films are considered
promising candidates exhibiting strong PMA. Burkert et al. predicted that a magnetic anisotropy energy may
increase in FeCo alloys when the tetragonal distortion is applied [1]. Remarkably, around a c/a ratio of 1.201.25, the magnetic anisotropy energy exceeds 700-800 μeV/atom, which is one or two orders of magnitudelarger than that of pure Fe or Co. The emergence of strong PMA was experimentally confirmed in thetetragonally distorted FeCo ultra-thin-films grown on Rh(001) (c/a = 1.24) with a thickness of 13-17
monolayers (ML) [2].
Generally, it is known that the band structure near the Fermi energy (EF) plays a very important role inachieving PMA [3,4]. The theoretical calculations suggest that the microscopic origin of PMA in thetetragonally distorted FeCo alloy is attributed to the minority-spin states composed of dxy and dx2-y2 orbitals
near EF, hybridized by spin-orbit interactions [1]. However, the spin- and orbital-dependent electronic statesof the tetragonally distorted FeCo alloy films are poorly investigated experimentally.
In this study, we have fabricated FeCo thin films on Rh(001) substrate by molecular beam epitaxy andinvestigated the spin-polarized electronic states by in-situ spin- and angle-resolved photoemission
spectroscopy (spin-ARPES) at BL-9B of Hiroshima Synchrotron Radiation Center [5]. The quality of thesample surface was checked by low energy electron diffraction and Auger electron spectroscopy. The
thickness of the film was 13.6 ML. We also carried out the first-principles calculations for the tetragonally
distorted FeCo alloy (c/a =1.24) with/without considering the spin-orbit coupling using WIEN2k program[6]. The exchange-correlation was treated using the generalized gradient approximation.
To determine the high symmetry points along kz direction [Fig. 1(a)], we first performed the photonenergy-dependent measurement. Figure 1(b) shows the ARPES image acquired at various incident photon
energies from 45 to 70 eV with s-polarization. We can recognize the mostly non-dispersive bands around EB= 1 eV with kz = 3.7 Å-1 and just below EF with kz = 4.4 Å-1. The observed features are reproduced by thecalculations (not shown here), and we determined that kz = 3.6 Å-1 (hν = 45 eV) corresponds to the Γ point.
Figure 1(c) shows the ARPES image along the Γ-X line recorded at 45 eV with p-polarization. A very steep
band crossing EF around the X point is recognized. In addition, weakly dispersive bands are found in between
EF to 1.0 eV around the Γ point.
To experimentally verify the spin-polarization, we next performed the spin-resolved measurements. The
sample was magnetized along (001) direction at room temperature prior to the measurements. Figures 2(a)and 2(b) display the out-of-plane spin-resolved energy distribution curves (EDCs) and spin-polarization
recorded at the Γ and X points, respectively. Here, red and blue represent the majority- and minority-spincomponents. For both momenta, we can clearly see the out-of-plane spin-polarization. At the Γ point, wehave observed a double peak structure in the minority-spin channel around EB = 0.2 and 0.6 eV, although thebroad feature can be seen in the wide energy range in the majority-spin channel [Fig. 2(a)]. On the other
hand, at the X point, a prominent majority-spin peak exists at EF [Fig. 2(b)]. These findings tell us that the
weakly dispersive bands around the Γ point and the steep band around the X point mainly comprise themajority-spin and majority-spin characters, respectively. Based on the theoretical investigations [2], themajority-spin states composed of dxy and dx2-y2 orbitals play an important role in the emergence of the PMAof the tetragonally distorted FeCo films. We finally compare the spin-ARPES results with the first-principles
calculations to scrutinize the orbital characters. Figure 2(c) shows the calculated band dispersion along theΓ-X line in the minority-spin channel. The radii of the orange (black) circles are proportional to the net
contribution of dxy (dx2-y2) orbital. By a comparison of Figs. 2(a), 2(b) and 2(c), it signifies that the observed
minority-spin peak located just below EF at the Γ point (black arrow) and at 1.1 eV at the X point (orange
arrow) are mainly attributed to the dx2-y2 and dxy orbitals, respectively.
In summary, we have investigated the spin-polarized electronic states of the FeCo/Rh(001) films by insitu spin-ARPES and first-principles calculations. The out-of-plane spin-polarization indicating the
emergence of PMA was clearly observed at room temperature with zero-field. We conclude that the minorityspin states near EF are mainly composed of dx2-y2 and dxy orbitals. Our findings provide the fundamental
properties of the FeCo thin films and pave the way for the PMA-based applications, such as the photoelectron
spin polarimeter, enabling the detection of the out-of-plane spin components.

FIGURE1 (a) Brillouin Zone of bct FeCo. (b) ARPES image of FeCo/Rh(001) film acquired from 45 to 75 eV with p-polarized
light. (c) ARPES image along the Γ-X line acquired at 45 eV with p-polarized light.

FIGURE2 (a) Out-of-plane spin-EDCs and spin-polarization at the Γ point. (b) Same as (a) but at the X point. (c) Calculatedband dispersion along the Γ-X line in the minority-spin channel. Black and orange represent the dx2-y2 and dxy orbitals,
respectively.

REFERENCES
1.
2.
3.
4.
5.
6.

T. Burkert et al., Phys. Rev. Lett. 93, 027203 (2004).
F. Yildiz et al., Phys. Rev. B 80, 064415 (2009).
P. Bruno, Phys. Rev. B 39, 865 (1989).
Y. Kota and A. Sakuma, J. Magn. Soc. Jpn. 37, 17 (2013).
T. Okuda et al., Rev. Sci. Instrum. 82, 103302 (2011).
P. Blaha et al., J. Chem. Phys. 152, 074101 (2020).

P20

23BU006

BL-9B

Ultrafast Spin-Dependent Dynamics
in a Carrier-Tuned Topological Insulator
K. Sumidaa, K. Kunitomob, M. Kakokib, K. A. Kokhc, O. E. Tereshchenkoc,
J. Reimannd, J. Güdded, U. Höferd, K. Miyamotoa, T. Okudaa,e, and A. Kimurab,eaHiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama,
Higashi-Hiroshima 739-0046, Japanb
Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama,
Higashi-Hiroshima 739-8526, Japanc
Physics Department, Novosibirsk State University, ul. Pirogova 2, 630090 Novosibirsk, RussiadDepartment of Physics and Materials Sciences Center, Philipps-University, D-35032 Marburg, GermanyeInternational Institute for Sustainability with Knotted Chiral Meta Matter (SKCM2), 1-3-1 Kagamiyama,
Higashi-Hiroshima 739-8526, Japan
Keywords: Topological insulator, Time-resolved ARPES, Spin-resolved ARPES, Ultrafast carrier dynamics, Spin texture.

Topological insulators (TIs) characterized by spin-polarized Dirac-cone-like band structures on theirsurfaces have been extensively investigated over the last decade. As a hallmark of TIs caused by strong spinorbit coupling, the spin-momentum-locked topological surface state (TSS) offers a pure spin current on theirsurfaces. The spin-polarized surface electrons of TIs are robust against nonmagnetic impurities and defects.
So far, many TIs, such as Bi2Se3, Bi2Te3, and Sb2Te3, have been theoretically predicted and experimentally
verified by angle-resolved photoemission spectroscopy (ARPES) with spin-resolution.
Recently, the ultrafast optical response of TSS has attracted much attention. Time-resolved ARPES
utilizing femtosecond-laser reveals several characteristics and functionalities, e.g., the emergence of Floquet
state [1], population inversion [2], and the surface photovoltage effect [3]. However, the ultrafast carrier
dynamics derived from the unique spin texture of TSS have hardly been investigated.
In this work, we investigated the spindependent ultrafast surface carrier dynamics ofa ternary topological insulator (Sb,Bi)2Te3,
where the Dirac point is adjusted to the Fermi
energy (EF), by a combination of laser-based
time-resolved ARPES and synchrotron-based
spin-resolved ARPES techniques. The pumpprobe time-resolved ARPES measurements
were performed at Philipps University of
Marburg. We used two different pump energies:
mid-infrared (MIR) at 0.30 eV and visible (VIS)
at 2.58 eV [Figs. 1(a) and 1(d)]. We used anultraviolet (UV) at 5.16 eV light as the probe.
The spin-resolved ARPES measurements,
utilizing very low energy electron diffraction
type spin-polarimeters, were performed at
ESPRESSO end-station (BL-9B) of Hiroshima
Synchrotron Radiation Center [4].
Figure 1(b) shows the ARPES image
FIGURE 1. (a) Schematic illustration of time-resolved
recorded at temporal overlap (t = 0 ps) with the
ARPES experiment using MIR-pump and UV-probe. (b)MIR-pump. We can recognize the Dirac-cone% direction
ARPES image of (Sb0.57Bi0.43)2Te3 along Γ" − Klike TSS and bulk conduction band above EF.
recorded at t = 0 ps. (c) Photoemission intensity profile as a
We also notice that the photoemission intensities
function of delay time. (d-f) Same as (a-c) but using VIS-pump.

at the TSS in a certain energy region around 0.05 eV are very weak [see the red arrow in Fig. 1(b)], while
those around 0.15 eV are pronounced. To illustrate the temporal evolution of the bands, Figure 1(c) displays
the momentum-integrated photoemission intensity profile as a function of delay time. We find a dip structurearound 0.05 eV from 0.0 to 0.5 ps. After 0.5 ps, the intensity around 0.05 eV drastically increases because
the photo-excited electrons at higher energy states relax through intra-band and inter-band scatterings. Thesefindings suggest that the direct transition is prohibited around 0.05 eV in the MIR-pump scheme. To compare
the ultrafast carrier dynamics, we also performed time-resolved ARPES using the VIS-pump [Figs. 1(e) and
1(f)]. However, in sharp contrast to the MIR-pump scheme, no dip structures are visible at t = 0 ps.
Since the forbidden transition observed in the MIR-pump scheme likely stems from the unique spin
texture of the TSS, we proceeded with the spin-resolved measurement of the occupied bands below EF.
Figure 2(a) shows the spin-resolved ARPES image captured at 17.0 eV. Red and blue colors correspond topositive and negative in-plane spin-polarization, respectively. From EF to -0.3 eV, the spin-polarized lower
portion of TSS is evident. Additionally, M-shaped spin-split Rashba bands are observed around -0.5 eV.
Since the directions of in-plane spin-polarization at the upper and lower TSSs are reversed with respect tothe Dirac point, the forbidden transitions in the “resonant” MIR-pump scheme are most likely caused by the
intrinsic spin texture of TSS, as depicted in Fig. 2(b). In the VIS-pump scheme, on the other hand, the directtransition to the upper TSS is allowed because the transition occurs from the unpolarized deeper-lying bulk
continuum states. Finally, we discuss why the direct transition is permitted around 0.15 eV at the TSS in the
MIR-pump scheme [Fig. 1(b)]. The upper panels of Fig. 2(c) show the constant energy contours recorded at
t ~ 0 ps with VIS-pump. At 0.05 eV, an isotropic shape contour is seen. On the other hand, at 0.15 eV, thecontour shape undergoes deformation from circular to hexagonal due to the warping effect. On the warped
bands, it is known that not only in-plane but also out-of-plane spin components emerge [the lower panels of
Fig. 2(c)] [5]. In such a case, the direct transition would be partially allowed.
In conclusion, we have experimentally demonstrated the spin-dependent forbidden transition in the TI by
using time-resolved ARPES and spin-resolved ARPES. Our findings pave the way for ultrafast optospintronic applications using the TSS of TIs.

% direction recorded at 17.0 eV. Gray
FIGURE 2. (a) In-plane spin-polarization mapping of (Sb0.57Bi0.43)2Te3 along Γ" − Kcircles represent the fitting results of the TSS shown in Fig. 1(e). (b) Schematic illustration of spin-dependent direct transition
using MIR- and VIS-pump schemes. (c) Upper panel: constant energy contours at 0.05 and 0.15 eV recorded at t ~ 0 ps with
VIS-pump. Lower panel: Schematic illustrations of spin texture of isotropic (left) and anisotropic TSS (right). Light green andorange colors correspond to the in-plane and out-of-plane spin components, respectively.

REFERENCES
1.
2.
3.
4.
5.

Y. H. Wang et al., Science 342, 453 (2013).
S. Y. Zhu et al., Sci. Rep. 5, 13213 (2015)., K. Sumida et al., Phys. Rev. B 99, 085302 (2019).
K. Sumida et al., Sci. Rep. 7, 14080 (2017)., T. Yoshikawa et al., Phys. Rev. B 100, 165311 (2019).
T. Okuda et al., Rev. Sci. Instrum. 82, 103302 (2011).
L. Fu, Phys. Rev. Lett. 103, 266801 (2009)., S. Souma et al., Phys. Rev. Lett. 106, 216803 (2011).

P21S

Laser Spin-ARPES

Demonstration of phase-resolved spin-ARPES on
topological surface states in
Towa Kousaa , T. Iwataa,b , S. Kumarc, A. Kimuraa,b ,K. Miyamotoc, T. Okudab,c and K. Kurodaa,baGraduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama,
Higashi-Hiroshima 739-8526, Japan.
bInternational Institute for Sustainability with Knotted Chiral Meta Matter(WPI-SKCM2),
Hiroshima University, Higashi-Hiroshima 739-8526, Japan.
c
Hiroshima Synchrotoron Radiation Center, Hiroshima University, 2-313 Kagamiyama,
Higashi-Hiroshima 739-0046, Japan

Keywords: Spin-orbit coupling, Topological surface states, Ultrafast dynamics

Optical transition such as photoemission takes place in attosecond scale (1 as = 10-18 s). It is very
interesting to phenomena in the attosecond region from point of view of the pursuit of ultimate understandingof quantum mechanics and pioneering electronics that can be controlled on as-time-scale. Great developmentof ultrashort pulse laser technology over the past few decades has permitted to track the ultrafast dynamics
as the attosecond scale in the time domain [1-4]. However, the ultrashort pulse nature of the attosecond pulse
diminished energy resolution because of a trade-off relationship between the pulse width in time andfrequency domains. This means that it is difficult to experimentally trace the ultrafast photoemission
dynamics together with resolving valance band structures.
In this work, to overcome the above difficulty, we attempted phase-resolved spin-ARPES [5-7] by laserbased angle-resolved photoelectron spectroscopy with 3D spin detection. Using this technique, we accessed
phase information in the transition matrix of the photoelectron states and its kinetic energy dependence thatcan be converted to the time scale of photoemission dynamics in as-time-scale [8]. For this measurement, apicosecond laser was used to achieve a 20-meV energy resolution for spin-ARPES and 3D spin detection
was used for the delay phase determination[9]. In addition, we built a polarization rotation control systemthat allows us to perform the automatic spin-ARPES measurements collecting a number of data points.
We studied the spin polarization of the photoelectrons emitted from the topological surface state of thetypical topological insulator Bi2Te3. The topological surface state is ideal for this experiment because they
form fully spin-polarized electronic states that are locked to be a helical texture in momentum space. Let us
also note that the spin-polarization of the photoelectron is collected on the mirror plane [Fig.1(a)], andtherefore the orbital selection rule is allowed in the photoemission process. Owing to these simple
experimental geometry, one can selectivity excite either even or odd orbital function that is coupled todifferent spin wavefunction [10] and superimposes these two dipole matrixes with the different spin inphotoelectron final state, resulting in the rotation of the spin polarization axis [5-7]. This process is
schematically summarized in Fig1.(b).
Though this process, the spin-orbit coupled wavefunction in the topological surface states allows us toselectively excite the spin and control its direction by photon polarization. Furthermore, the spin direction
as a function of the photon polarization sensitivity depends on the relative phase between the two matrix
elements, which therefore allows us to extract the phase from our spin-ARPES data. The extracted relative
phase
between two transition is used for time conversion according to the Eisenbud-Wigner-Smith(EWS) model [1,11] :
=ℏ
where

is a time delay obtained in the EWS-model, and(1)
is kinetic energy of the photoelectron.

Fig2.(a) represents a Fermi surface and ARPES of the topological surface states in Bi2Te3. Fig2.(b)represents the results of photoelectron spin interference performed at each of wavenumbers k1~k4 in Fig2.(a).
Also, we just give a brief description here, a slight correlation is observed between each phase and kinetic
energy, indicating that phase decomposition is possible. Using its data and Eq.(1), we obtained the result thatthe delay time= 1.29 10
s.
..(b)

(a)

. .(c)[Fig1.] (a) Electron orbitals and spins of topological surface states on the mirror plane. (b) Concept of photoelectron spin
interference. (c) Concepts that tie our work to EWS model [5-7,11]. The wave packets of two transition are scattered differently
as they pass thorough the potential V, therefore
occurs between the two transitions. We noted thatis extracted for each
Ek andis calculated from Eq.(1).

.(b)

(a)

[Fig2.] (a) ARPES of topological surface states in Bi2Te3. Temperature is 40~50K. Photon energy is 6.3eV. Photon is liner
polarization. k1~k4 are wavenumber of each spin detection. Clean surface was obtained by cleaving in 7.3 10 Pa. The
mirror plane (Γ- M direction), the detection plane and the slit direction are all parallel. (b) Spin detection with polarization
rotation at binding energies corresponding to each wave number. Sseff = 0.27. The dots are experimental values, and the solidlines are model fittings [5-7].

REFERENCES
1. E. P. Wigner, Phys. Rev vol 98 145 (1955).
2. Paul, P. M et al., Science 292, 1689-1692 (2001).
3. Hentschel, M et al., Nature 414, 509-513 (2001).
4. Schultze, M et al., Science 328, 1658-1662 (2010)
5. K. Kuroda et al., Phys. Rev. 94, 165162 (2016)
6. K. Kuroda et al., Phys. Rev. B. 105, L121106 (2022)
7. K. Yaji et al., Nature. communications. 8, 14588 (2017)
8. M. Fanciulli et al., Phys. Rev. Lett. 118, 067402 (2017)
9. T. Iwata et al., Scientific Reports 14:127 (2024)
10. J. Henk et al., Phys. Rev. B. 68, 165416 (2003)
11. F. T. Smith et al., Phys. Rev. 118, 349 (1960)

P22S

Laser SARPES

Performance of laser-based SARPES
with micrometer spatial and vector spin resolution at HiSOR
A, B

Takuma Iwata, A T. Kousa, A Y. Nishioka, A K. Ohwada, C K. Sumida,D
E. Annese, A M. Kakoki, A, B K. Kuroda, E H. Iwasawa, C M. Arita, C S. Kumar,
A, B
A. Kimura, C K. Miyamoto and B, C T. Okuda
A

Grad. Sch. Adv. Sci. Eng., Hiroshima Univ. 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, JapanB
WPI-SKCM2., Hiroshima Univ., 2-313 Kagamiyama, Higashi-Hiroshima, Japan 739-0046
C
HiSOR, Hiroshima Univ. 2-313 Kagamiyama, Higashi-Hiroshima 739-0046, JapanD
Brazilian Center for Research in Physics, Rua Dr. Xavier Sigaud 150,
Rio de Janeiro, RJ 22290-180, Brazil
E
Institute for Advanced Synchrotron Light Source, National Institutes for Quantum Science andTechnology, Sendai 980-8579, Japan

Keywords: Spin-and angle-resolved photoemission spectroscopy, electronic structure, spin polarization, momentum space

Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool to directory observe the electronic
structure of solids. In recent years, micro-ARPES [1] which is combined with a micro-focused light source
has attracted much attention, since it is found to very useful to explore the electronic states in newly
topological materials [2], phase-separated correlated systems [3] and transcription samples [4].
Spin-resolved ARPES (SARPES) [5] enables us to detect not only the energy and momentum but also thespin of photoelectrons owing to recent development of the spin detectors. However, micro-SARPES
measurement has never been reported so far, because of the difficulties of the spin detection and its
combination technique. Synchrotron Radiation is a conventional light source used for SARPES. Although
there are some synchrotron radiation based micro- (or nano-)ARPES systems, the use of special opticalelements (such as Fresnel zone plate) attenuate intensity of light and the need for a mechanism to control the
optical system under ultrahigh vacuum condition make micro-SARPES a difficult and still developing
technology.
In this context, we employed a high-photon flux ultraviolet laser with 6-eV of photon energy instead ofsynchrotron radiation to realize micro-SARPES. In addition to high photon flux, the advantage of the 6-eVlaser is the flexibility of its optical system due to high atmospheric transmission. Since SARPES requires anintense light source to perform high resolution measurements, we considered a laser to be the best lightsource for micro-SARPES. Therefore, we combined a high-intensity 6-eV laser with a high-efficiency spin
detector at HiSOR to develop micro-SARPES machine that can perform high-efficiency spin-resolved
experiments while maintaining micro-focusing.
In this presentation, we will describe the performance of the-state-of-the-art micro-SARPES machine
combining 6-eV laser source and the photoelectron analyzer equipped with the electron deflector function
and two VLEED type spin detectors [6]. We evaluated spatial resolution and long-time stability using an Au
polycrystalline letter pattern (“µ-SARPES”) sample, which is fabricated on a Si substrate using photo
lithography (Fig. 1). We performed not only 3D spin-resolved experiment to Bi2Te3, which is a typical
topological insulator as a test sample, but also spin- and spatial-resolved experiment to PbBi4Te4S3 [7], which
has two Dirac-cone-like dispersions derived from two distinct terminations (Fig. 2).

FIGURE 1. Characterization of the spatial resolution. (a) The optical microscope image of the Au pattern on the Si (001)substrate. (b) The image of the scanning photoelectron intensity map (SPEM) taken in the Au pattern. (c) and (d) Photoelectron
intensity profiles at the edges of the Au pattern along the x (horizontal) and y (vertical) axes, respectively (green and blue lines
in the insets). (e) Plots of the intensity deviation ΔI(x) and ΔI(y) as a function of time to evaluate possible long-term drifts of
the laser and the sample stage. The data was recorded at the intensity edge at xc and yc denoted by arrows in (c) and (d). The
1~µm of the drift along x (y) axis can correspond to 19% (10%) of ΔI(x); [ΔI(y)] guided by dashed lines.

FIGURE 1. Demonstration of spatially-resolved SARPES measurements on PbBi4Te4S3 (a) Optical microscope image of acleaved surface of PbBi4Te4S3. (b) SPEM image taken with a 50 µm step. (c) Spatially-resolved ARPES images acquired at
different surface terminations [7]. (d) Scanning ARPES intensity map measured at the 100×100 µm marked by the red squarein (b). The map is taken by scanning 2 µm and 10 µm steps along x and y axes, respectively.

REFERENCES[1] H. Iwasawa et. al., Ultramicroscopy, 182, 85 (2017).
[2] R. Noguchi et al., Nature, 566, 518 (2019).
[3] K. Kuroda et al., Nature Communications, 11, 2888 (2020).
[4] I. Cucchi et al., Nano Letters, 19, 554 (2019).
[5] T. Okuda et. al,. J. Phys.: Condens. Matter, 29, 483001 (2017).
[6] T. Iwata et. al., Scientific Reports, 14, 127 (2024)[7] K. Sumida et. al., Physical Review materials, 2, 104201 (2018)

P23

23AG031 and 23AG032

BL-1/BL-9A/Laser-SARPES

Direct Observation of Spin-split Electronic Structuresin Antiferromagnet NdBi by Laser-based SARPES
Rikako Yamamoto a, T. Motoyamab, T. Iwataa,b, T. Kosab, Y. Nishiokab,
K. Ideurab, M. Aritac, S. Idetac, K. Shimadaa,c, K. Miyamoto c,T. Okudaa,c, A. Kimuraa,b, T. Onimaru b, and Kenta Kurodaa,baInternational Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM2 ),Hiroshima University, Higashi-Hiroshima 739-8526, Japanb
Graduate School of Advanced Science and Engineering, Hiroshima University,
1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japanc
Hiroshima Synchrotron Radiation Center, Hiroshima University,
2-313 Kagamiyama, Higashi-Hiroshima 739-0046, Japann

Keywords: rare-earth monopnictide, spin-resolved and angle-resolved photoemission spectroscopy, spin textures

Rare-earth monopnictides RX (R: Rare-earth, X: N. P, As, Sb, and Bi) have attracted much attention
because of their topological electronic structures [1,2] and unusual magnetic transitions [3,4]. Recently,
unconventional surface states have been reported in the antiferromagnet NdBi. The surface states, consistingof sharp Fermi-arc-like hole bands and electron bands near Fermi energy E F, appear below theantiferromagnetic (AFM) transition at TN = 24 K [5]. Density functional theory calculations suggest that themulti-q magnetic structures induce the surface states inside the band-folding hybridization bulk gap [6].
Although the discovery of the unconventional surface states stimulates intense discussion on their origin, thekey information on the spin polarization is still missing.
Here, we investigated the electronic structure and the spin polarization of the unconventional surface
states. The experiments were performed synchrotron-based angle-resolved photoemission spectroscopy(ARPES) by BL-1 and BL-9A and laser-based spin-resolved ARPES (SARPES) at Hiroshima Synchrotron
Radiation Center. The Fermi surface in the paramagnetic state has a square and a surrounding rhomboid hole
pocket centered in the Brillouin zone. On cooling below TN, the electronic structure is reconstructed and thesurface states appear, which is consistent with previous reports [7,8]. In addition, we successfully observed
different electronic structures depending on the magnetic domain: while the electron bands were recognizedalong the kx direction, those appear along perpendicular to the kx direction in different measurement areas.
To obtain the spin information of the surface state, we conducted SARPES measurements. It is revealed thatspin polarization for the hole and electron bands emerging in the AFM state is the opposite: the hole andelectron bands show negative and positive spin polarization, respectively. Moreover, the spin-resolved
measurements of the in-plane spin component demonstrated spin polarizations exceeding ±50%. Our results
fill the gap between experimental and theoretical studies and enable us to further understand the origin of
the unconventional surface states.

REFERENCES
1. J. Nayak et al., Nat Commun. 8, 13942 (2017).
2. K. Kuroda et al., Phys. Rev. Lett. 120, 086402 (2018).
3. K. Kuroda et al., Nat Commun. 11, 2888 (2020).
4. Y. Arai et al., Nat. Mater. 21, 410 (2022).
5. B. Schrunk et al. Nature 603, 610 (2022).
6. LL. Wang et al., Commn. Phys. 6, 78 (2023).
7. Y. Kushnirenko et al., Phys. Rev. B 108, 115102 (2023).
8. A. Honma et al. Nat Commun. 14, 7396 (2023).

P24

21AG028, 21BU002, 22AG009

BL-12

Secondary Structural Changes of FUS-LC induced with
Phase-Separation observed by VUV-CD
Kentaro Fujiia, Nobuo Maitaa, Koichi Matsuob, and Masato KatoaaInstitute for Quantum Life Science, National Institutes for Quantum Science and Technology,
4-9-1 Anagawa, Inage-ku, Chiba-city, Chiba, 263-8555 JAPANb
Hiroshima Synchrotron Radiation Center, Hiroshima-university,
2-313 Kagamiyama, Higashihiroshima-city, Hiroshima, 739-0046 JAPAN

Keywords: Liquid-Liquid Phase Separation, FUS-LC, Secondary structural changes.

Aggregation of the RNA-binding protein FUS (Fused in Sarcoma) has been implicated inneurodegenerative diseases such as ALS (amyotrophic lateral sclerosis) and FTD (frontotemporal dementia).
The low-complexity domain of the FUS (FUS-LC) mediated liquid-liquid phase separation (LLPS), but thestructural mechanism is not known in detail. To address the revealing mechanism, we examined thespectroscopic study using VUV-CD measurement, which can analyze the secondary structure of the proteins.
CD measurements were performed at BL12 VUV-CD station in HiSOR. CD spectra were measured
between 185 and 260 nm. The temperature of the samples was controlled from room temperature to 5℃ toobtain the LLPS of the FUS LC.
The CD spectrum obtained by measuring at room temperature has a prominent peak at 195 nm and a small
shoulder peak near 220 nm. This shows that the major structure is a random coil since the spectrum was
similar to that of STI, which is mainly an unordered structure. This result is consistent with that obtained
from NMR measurement. The peak intensity around 195 nm decreased by cooling the sample temperature.
The reasons for the obtained spectral changes are as follows; 1) LLPS showed secondary structural changes,
2) LLPS made an effect to decreasing the transmission light intensity by scattering of suspension. We
examine the measurement by changing the relative distance between the cell and the photo-multiplierdetector. This may clarify the contribution of the scattering effect on the obtained spectrum.

P25

23AG028

BL-12

Insights into Physical Interactions and Structuration in
Self-Assembled Azapeptide Hydrogels ThroughSpectroscopy Techniques
Mohamed Ibrahima,b, Jacques Bodiguelb, Marie-Christine Averlant-Petitb, andKoichi Matsuoa
aHiroshima Synchrotron Radiation Center (HiSOR), Hiroshima University, 2-313 Kagamiyama, HigashiHiroshima, Hiroshima 739-0046 Japan.
b
Université de Lorraine, CNRS, LCPM, F-54000 Nancy France.

Keywords: Self-Assembly, Azapeptides, Hydrogels, Circular Dichroism.

Self-assembly is a captivating phenomenon within supramolecular chemistry, triggering the formationof hydrogels stabilized by non-covalent interactions including hydrogen bonding, π-π stacking, electrostaticinteractions, and hydrophobic forces. Supramolecular gels-based low molecular weight molecules findapplications in tissue engineering, drug delivery, biosensing, and catalysis [1]. Azapeptides, characterized
by their nitrogen atoms, offer unique functionalities and stability, rendering them ideal for the fabrication of
supramolecular hydrogels [2, 3]. In this study, two hydrogelator molecules derived from azapeptide family
were designed, and structurally elucidated using various spectroscopic techniques. NMR, FTIR, UV-Vis,
fluorescence, SEM, and rheology experiments were conducted to explore molecular, supramolecular,
mechanical features. In solution, both molecules exhibit monomeric states adopting β-turn conformation
stabilized by intramolecular hydrogen bonding, while the supramolecular structure (as revealed by X-ray
crystallography) is stabilized mainly through intermolecular hydrogen bonding and π-π stacking (data is notshown). In the gel state, circular dichroism (CD) spectroscopy, is crucial for understanding the secondary
structure and self-assembly of azapeptide-based hydrogels [4]. This study sheds light on the conformationalchanges occurring during the self-assembly
process. For example, the temperature dependent
experiment revealed the gel-sol transition
associated with conformational changes (seeFigure 1). By integrating principles fromsupramolecular chemistry, innovative azapeptide
design strategies, and sophisticated spectroscopic
methodologies, the development of functionalhydrogels with tailored properties for diverse
applications becomes achievable.
FIGURE 1. Temperature-dependent SRCD spectrum of
azapeptide hydrogel (c = 0.8 w/w%, pH = 7.0).

REFERENCES
1.
2.
3.
4.
5.

M. J. Webber, E. A. Appel, E. W. Meijer, R. Langer, Nature Materials, 2016, 15, pp. 13–26.
F. Rodríguez-Llansola, B. Escuder, J.F. Miravet, Chemical Society Reviews, 2015, 44, pp. 6058–6071.
E. R. Draper, M. Wallace, S. Ladame, Chemical Society Reviews, 2020, 49, pp. 7134–7171.
N. Berthet, P. Dugourd, R. Antoine, S. Lecomte, Chirality, 2019, 31, pp. 458–476.
M. I. A. Ibrahim, G. Pickaert, L. Stefan, B. Jamart-Grégoire, J. Bodiguel, M.-C. Averlant-Petit, RSC Advances,
2020,10, pp. 43859-43869.

P26S

23AG011

BL-12

Monitoring the Self-Assembly of Alginate Hydrogel Using
Synchrotron Radiation Circular Dichroism
Tatsuki Hagaa, Masaya Yoshida, Takeharu Hainoa, Koichi Matsuob andMohamed I.A. IbrahimbaGraduate School of Advanced Science and Engineering, Hiroshima University.
Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima University, 2-313 Kagamiyama, HigashiHiroshima, Hiroshima 739-0046 Japan.

b

Keywords: Alginate, Hydrogel, Self-Assembly, CD, AFM

Circular dichroism (CD) spectroscopy, traditionally used for studying the secondary structure of proteinsand peptides [1], has not been yet established for studying polysaccharides (PSs). The current study has
explored the potential of using CD in structural changes associated with PS hydrogelation. Certain PSs canchange from a liquid to a gel when exposed to light, ions, or temperature. Alginate, an ecofriendly andnontoxic PS used in medicine and food, is especially known for forming hydrogels when mixed with
polyvalent ions [2]. In the food industry, alginate serves as an additive to enhance texture and shape. Thisfunction is closely related to the conformational changes during sol-gel transitions, so structural analysis ofalginate is helpful for maximizing its function as an additive.
Herein, CD experiments using synchrotron radiation (SR) light were carried out to investigate thestructural changes associated with gel formation in the presence and absence of metal ions. Monovalent ionssuch as Na+, K+, and Li+ did not induce hydrogel formation, whereas hydrogels were obtained by divalents(e.g., Ca2+, Ba2+, Cu2+, and Zn2+), as well as trivalent ion (e.g., Fe3+). The cations exhibited different
influences on the native conformation of alginate, suggesting variations in the assembly of the alginate chainsin the presence of different ions. Additionally, discrepancies in CD spectra reflected that the formedhydrogels possessed diverse mechanical, physical properties, and morphology.
The formulation of hydrogels is an evidence of the self-assembly phenomeneon. Alginate chains are interconnected, forming a cross-linked 3D-network structure that entraps water molecules, leading to hydrogel
formation. Hence, to construct the self-assembly/gel phase diagram based on the CD observations,concentration-dependent experiments, varying alginate concentrations or polyvalent ion concnetrations (i.e.,Ca2+), were conducted using a CD spectrometer. The concentration of the polyvalent ion that causes nochange in the CD spectrum of alginate or that self-assembly of alginate chains was terminated (Figure 1,
left) was marked as the initiation of aggregation. As a result, a Ca2+ concentration of 1.56 mM, at 1.0 mg/ml
alginate concentration, was referred to the transition concentration from the self-assembly to aggregation
which is followed by hydrogel formation (Figure 1, right). This finding was reinforced by atomic force
microscopy (AFM) imaging, which showed increased cross-linking and thichness of fibers at higher Ca2+
concentration (2.5 mM) (Figure 2).

FIGURE 1. CD spectrum of alginate (1.0 mg/ml) as a function of Ca2+ concentrations (0.5 mM ~ 2.5 mM) (left), and selfassembly transition diagram based on CD observations (right).

FIGURE 2. AFM images of the alginate-Ca2+ system with [alginate] = 1.0 mg/ml and Ca2+ concentrations of 1.0 mM (left),or 2.5 mM (right).

Ongoing investigations are underway to further explore the alginate-Ca2+ hydrogel system using SRCD,
aiming to study the kinetics and thermodynamics of hydrogelation process.

REFERENCES[1] K. Matsuo, G. Kunihiko, Bulletin of the Chemical Society of Japan, 2013, 86, 675-689.
[2] J. Brus, M. Urbanova, J. Czernek, Biomacromolecules, 2017, 18, 2478–2488.

P27S
BL-12

22BG016VUVCD Measurements of dried proteins and its
application to protein-membrane interaction study
Kosuke Hayashia, Ryota Imauraa, and Koichi Matsuoa,bGraduate School of Advanced Science and Engineering, Hiroshima University
Hiroshima Synchrotron Radiation Center, Hiroshima University, Hiroshima Universityab

Keywords: circular dichroism, G3LEA protein, membrane, spin coat, secondary structure

Proteins in the dry state are utilized in various fields such as pharmaceuticals and food science. It is known
that the structural differences between the liquid and dry states are slight for globular proteins [1], but
intrinsically disordered protein undergoes a structural alternation from non-regular to regular structuresduring the dry process, expressing some unique biological functions. Hence, the elucidation of therelationships between the structural alternation and the function expression is attractive targets. In this study,
we measured some globular proteins in the dry state using a vacuum-ultraviolet circular dichroism (VUVCD)
spectroscopy, which is the powerful tool for secondary structure analysis of proteins, to discuss the
preparations methods of dried proteins. Further, we measured the VUVCD spectra of dried G3LEA protein,which has the structural alternation from disordered structure in liquid state to helical structure in the dry
state, expressing a protective function of cell membrane [2].
Eight types of dried globular proteins with different secondary structures were prepared by a spin coating
technique and a vacuum drop casting method. As expected, the spin coating can suppress the surface
inhomogeneity of the samples compared the drop casting, depressing the artifact within the CD data due tolinear dichroism, which were confirmed by the suppression of rotation and inversion CD dependence ofdried samples. Dried G3LEA consisting of 22 residues wereprepared by the spin coating technique and we confirmed
the structural alternation from random structure in liquidstate to α-helix structure in the solid state (Figure 1). The
CD spectra of dried G3LEA protein were also measured in
the presence of two types of liposomes which are composedof net neutral or negatively-charged phospholipids. As aresult, the formation of α-helix structures was clearlyobserved in negatively-charged lipid liposome but not inneutral one. Furthermore, the formation of α-helix
structures was further promoted in the lipid liposome of thegel phase, compared to that of the liquid crystal phase.
These results indicated that the surface charge of liposome
and its liposome fluidity influenced the structural
alternations of dried G3LEA protein.
FIGURE 1 VUVCD spectra of G3LEA protein

REFERENCES
1. J.S Yoneda, A. J.Miles, A.P.U. Araujo, and B.A. Wallace, Differential dehydration effects on globular proteins andintrinsically disordered proteins during film formation, Protein Sci., 26, 718-726(2017)
2. T. Furuki, M. Sakurai, Group 3 LEA protein model peptides protect liposomes during desiccation, Biochim. biophys. acta
1838, 2757-2766(2014)

P28
23AU007

BL-12

Optical Activity Measurement of Circularly Polarized
Lyman-α Light Irradiated and Magnetic Field Applied
Amino-acid Films
Jun-ichi Takahashia, Masahiro Kobayashib, Gen Fujimoric, Hiroshi Otad
Koichi Matsuoe, Yoshitaka Tairad, Masahiro Katohd,e, Kensei Kobayashic,fYoko Kebukawaf, Hiroaki NakamurabaDoshisha University, 1-3 Tatara Miyakodani, Kyotanabe 610-0394, Japan
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japanc
Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, JapandUVSOR Synchrotron Facility, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japane
Hiroshima Synchrotron Radiation Center, 2-313 Kagamiyama, Higashi-Hiroshima 739-0046, Japanf
Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8511, Japanb

Keywords: Homochirality, Amino Acid, Optical Activity, Circularly Polarized Light, Lyman-α, Circular Dichroism.

The origin of homochirality in terrestrial biomolecules (L-amino acid and D-sugar dominant) remains
one of the most mysterious problems in the research for the origins of life. Rational explanations for thechiral asymmetry introduction into biomolecules are required through interdisciplinary collaborations. Oneof the most attractive hypotheses in the context of astrobiology is cosmogenic scenario; Asymmetric
reactions of prebiotic molecules on interstellar dust surfaces in molecular cloud circumstances wereintroduced by polarized quantum radiation sources in space, that is “chiral radiations” [1, 2].
Among the polarized quantum radiation sources, circularly polarized light (CPL) in the spaceenvironment is thought to be one of the most likely causes of the enantiomeric excesses of terrestrial
bioorganic molecules. A cosmogenic scenario has attracted attention, which proposes that the radiation fieldsof CPL induce new optical activity in organic molecules produced in the interstellar environment, leading to
the enantiomeric excesses. The radiation fields of CPL are assumed to exist in the scattered light by magnetic
field-aligned dust in massive star-forming regions [3] and in synchrotron radiation (SR) or gamma-ray bursts
from neutron stars with strong magnetic fields [2]. Ultraviolet light with a wavelength shorter than 230 nm
is highly absorbed by bioorganic molecules such as amino acids. Furthermore, this is in the region where theoptical response to left- (L-) and right- (R-) CPL is of opposite sign, that is, optical activity is prominent.
To validate the cosmogenic scenario, several ground simulating experiments have been investigatedusing ultraviolet CPL from high-energy particle accelerators. In this study, we focused on a hydrogen Lymanα wavelength of 121.6 nm, where strong emission lines are observed in star-forming regions. Furthermore,
it is predicted by recent theoretical calculations that the hydrogen Lyman-α light is circularly polarized by
the magnetic field-aligned dust scattering in massive star-forming regions. We have carried out irradiation
experiments by using circularly polarized hydrogen Lyman-α light to investigate the further photon energy
dependence of chiral asymmetric reactions. We formed thin solid film samples of racemic mixture of alanine(DL-alanine) on quartz substrates from crystal powders of DL-alanine by using a thermal-crucible vacuumevaporation system. The samples were irradiated with L- or R-CPL in hydrogen Lyman-α wavelength of
121.6 nm using the undulator beam line BL1U of UVSOR-III. The irradiated CPL wavelength corresponds
to photon absorption bands with the chromophores from the electronic transitions of carboxyl and aminogroups (π-σ*) of alanine molecule [4, 5]. The samples were set in a vacuum sample chamber preventing
attenuation by air absorption. The 121.6 nm wavelength radiation from the undulator is reflected by a goldcoated mirror located in the mirror chamber directly beam upstream of the sample chamber and then enters
the sample chamber. On the beam entrance side of the vacuum sample chamber, a gate valve with an MgF2
vacuum sealing window (0.5 mm in thickness) was mounted. The use of gold-coated mirror reflections hasmade it possible to suppress high-energy higher-order light from the undulator source expecting to reduce
the transmittance loss of the MgF2 window due to high-energy radiation induced defects. The sample
substrate was set in the sample holder, in which magnetic field can be applied to perpendicularly to thesample surface (Figure 1). The total photon beam intensity irradiated on the sample was monitored withphotoelectron current of a silicon photodiode settled at the beam downstream side of the sample holder.
CD spectra of the CPL irradiated films were measured using the SR-CD beam line BL-12 of HiSOR toclarify the optical activity emergence by CPL irradiation. CD spectroscopy can detect optical activity with ahigh accuracy because CD spectra sensitively reflects the steric structures of chiral molecules. To delete theeffects of linear dichroism components, the CD spectra at sample rotation angles (0, 45, 90, and 135 degrees)from both back and front directions of each were individually measured and averaged them. We alreadyreported the results of the first feasibility study conducted as application proposals to collaborate withUVSOR and HiSOR in FY2022 (6). The measured CD spectra of DL-alanine films irradiated with CPL at
121.6 nm in wavelength indicated the emergence of optical activity depending on the irradiated CPL
polarization helicity (L- or R-CPL). In addition, we examined the effect of applying a magnetic field to thesample to investigate the effect of the magnetic field in interstellar space. Comparing with CD spectra ofirradiations at 215, 180 and 155 nm in wavelength in our previous study [7, 8], the aspects of the opticalactivity emergence strongly depend on the irradiated CPL wavelength.
In the experiments for the FY2023 collaborative application proposals, we focused on accumulating
reproducibility data of the previous FY2022 results and improving the accuracy of quantification in thequantum efficiency of the emergence of optical activity. Figure 2 shows CD spectra of DL-alanine films afterright (R-) and left (L-) circularly polarized Lyman-α (121.6 nm) irradiation with magnetic field (0, ±0.7 T).
As shown in this figure, we found a clear emergence of optical activity and a significant magnetic field
application effect. The clarification of full mechanism of the optical activity emergence potentially has
relevance to the origin of terrestrial bioorganic homochirality stimulated by “chiral photon radiation”.
This work is supported by the Astrobiology Center Program of National Institutes of Natural Sciences(NINS) (Grant Number AB041014 and AB0515) and Frontier Photonic Sciences Project of National
Institutes of Natural Sciences (NINS) (Grant Number 01212202 and 01212304).

FIGURE 1. Schematic view of circularly polarized Lymanα (121.6 nm) irradiation system.

FIGURE 2. CD spectra of on DL-alanine films after right(R-) and left (L-) circularly polarized Lyman-α irradiation
with magnetic field (0, ±0.7 T).

REFERENCES
1. W. A. Bonner, Orig. Life Evol. Biosph. 21, 407 (1991).
2. J. Takahashi and K. Kobayashi, Symmetry 11, 919 (2019).
3. H. Fukushima, et al., Month. Notices Roy. Astron. Soc. 496 2762 (2020).
4. M. Tanaka et al., Enantiomer 7 185 (2002).
5. F. Kaneko et al., J. Phys. Soc. Jpn. 78 013001 (2009).
6. M. Kobayashi et al., in Proceedings of A joint ISSOL/IAU-Astrobiology Commission Meeting Origins 2023, Quito, 2023.
7. J. Takahashi et al., Int. J. Mol. Sci. 10, 3044 (2009).
8. J. Takahashi et al., HISOR Act. Rep. 2019 p.120 (2020).

P29S

23BU005

BL-6

Molecular orientation in polymer/fullerene blend films
studied by NEXAFS
Y. Hanakia, H. Yoshidab,c and T. Sekitanib,caFaculty of Science, Hiroshima University
Graduate School of Advanced Science and Engineering, Hiroshima Universityc
Hiroshima Synchrotron Radiation Center, Hiroshima Universityb

Keywords: fullerene, polymer, solar cell, NEXAFS

With the increasing demand for renewable energy, organic photovoltaics have attracted muchattention due to the low cost, lightweight and flexibility in recent years. Polymer solar cells based on bulk
heterojunction (BHJ) consisting of interpenetrating networks of conjugated polymers as electron donors
and fullerene derivatives as electron acceptors, are being developed for their potential application [1]. They
provide a large interfacial area where efficient exciton dissociation can occur. The morphology of BHJ
plays an important role in obtaining high efficiency organic photovoltaic devices. The order andorientation of the polymer backbone in the bulk heterojunction can influence device properties, such as theexciton diffusion, and charge carrier transport.
In this study, the molecular orientation of polymer/fullerene blend film was examined by near edge
X-ray absorption fine structure (NEXAFS) spectroscopy.
Poly-{bi(dodecyl)thiophenethieno[3,4-c]pyrrole-4,6-dione} (PBTTPD) was used as electron donor, and (6,6)-phenyl-C61-butyric acidmethyl ester (PCBM) is used as electron acceptor. Figure 1 show the molecular structures of PBTTPD and
PCBM. The blend of poly-3-hexylthiophene (P3HT) and PCBM has been used as a model system in BHJ
solar cells. Compared with P3HT, PBTTPD is co-polymer which has donor and acceptor in the main chain
and the higher power conversion efficiency of PBTTPD blend film is reported [2].
Samples for NEXAFS measurement were spin-coated on the gold coated silicon substrate from eachsolution. Pure PBTTPD PCBM, and blend of PBTTPD:PCBM (1:1.5 by weight) were dissolved inchloroform. NEXAFS measurements were performed at BL6 of Hiroshima Synchrotron Radiation Center.
Oxygen K-edge NEXAFS spectra were measured for PBTTPD, PCBM and PBTTPD: PCBM blend
films. Figure 2 shows the NEXAFS spectra of blend films. Red line shows spectrum of normal incidence
and black line shows that of grazing incidence. First strong peak come from *C=O resonant excitations ofboth PBTTPD and PCBM. NEXAFS spectrum of blend film was well reproduced by the superposition of
PBTTPD and PCBM. From the angular dependence of *C=O excitation, orientation angle of eachmolecule was obtained. Both PBTTPD of pure and blend films show “edge-on” orientation, which has
the plane of polymer backbone perpendicular to the substrate. The effect of the coexistence of PCBM is
considered small for polymer orientation which is important for charge transport process.

(a)

(b)

FIGURE 1.

Molecular structures of (a) PBTTPD and (b) PCBM.

20deg90deg

2.5

Intensity（a.u.）

2
1.5
1
0.5
0
-0.5
520

525

530

535

540

545

550

555

560

Photon Energy（eV）
FIGURE 2. Oxygen K-edge NEXAFS spectra of PBTTPD:PCBM blend film measured at different incidence angle.

REFERENCES
1. G. Yu, J. Gao, J. C. Hummulen, F. Wudl, A.J. Heeger, Science 270, 1789 (1995).
2. M. S. Su, C. Y. Kuo, M. C. Yuan, U. S. Jeng,; C. J. Su, K.-H. Wei, Adv. Mater. 23, 3315 (2011)

P30S

22BG044, 23BG033

BL-13

Charge Transfer in Gold Substrates and Nanoparticles Coatedwith Methyl Ester Substituted Aromatic Thiol Molecules
Shogo Tendo1, Akinobu Niozu1, Kakuto Yoshioka1, Jun-ichi Adachi2,
Hirokazu Tanaka2, and Shin-ichi Wada1,3
1

Graduate School of Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan2
Photon Factory, Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan
3
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
Keywords: Self-assembled monolayers (SAMs), Gold nanoparticles, Site-selective desorption, Core-hole-clock (CHC)

Charge transfer between molecules and metal surfaces
is a crucial process with implications for molecularelectronics, energy storage, and catalysis. Particularly in
nanoparticle films deposited on substrates, where organic
molecules coat gold nanoparticles (AuNPs), chargetransfer between π-conjugated molecules and metal playsa pivotal role in determining the photoelectric conversion
efficiency of dye-sensitized solar cells. In this study, we
focused on oligophenyl molecules, which have different
molecular lengths, and directly measured the chargetransfer time using soft X-rays (Figure 1 (a)–(c)) [1].
Subsequently, we elucidated the electronic properties of
the nanoparticle films by comparing the charge transfer
dynamics from molecules to flat metal surfaces.
Monophenyl
andbiphenylself-assembled
monolayers (MP and MBP SAMs, Figure 1 (a), (b)) wereprepared on two different metal surfaces. The first SAMs
were formed on two-dimensional flat gold substrates (2DSAMs, Figure 1 (d)). The second SAMs were formed on
three-dimensional AuNPs, which were drop-cast onto thesubstrates (3D SAMs, Figure 1 (e)). AuNPs weresynthesized by pulsed laser ablation in liquid. The size of
the AuNPs was determined to be 7 nm from the surface
plasmon resonant peak wavelength, as shown in Figure
2, based on the analytical equation.
Near-edge X-ray absorption fine structure (NEXAFS)
spectra and X-ray photoelectron spectra (XPS) werecollected at the HiSOR BL-13. The XPS results for the
2D-MP and 3D-MBP SAMs are presented in Figure 3.
An important observation from XPS is the similarity inchemical shifts, with no clear discrepancy in the energy
position between 2D and 3D SAMs. Any slight variations
were attributed to the inhomogeneity of the NP surfaces;
nevertheless, the electronic structures of the 2D and 3D
SAM remained identical. Figure 4 shows the C and O Kedge NEXAFS spectra. The dominant peaks included
π*(C=C) at ~285 eV for the C K-edge and π*(C=O) at
532.0 eV for the O K-edge. Polarization angular

(a)

(b)

(d)

(c)

(e)

Au
Au

FIGURE 1. Molecular structures of (a) MP and (b)MBP. Images of (c) charge transfer process, and(d) 2D-MP, and (e) 3D-MP SAMs.

FIGURE 2. UV-VIS spectrum of AuNP colloids.

FIGURE 3. XPS of 2D-MP and 3D-MP SAMs.

dependence was observed in 2D-MP, and the subsequentfitting analysis suggested that the molecules adsorbed in
an upright orientation to the surfaces [2]. In contrast, thisphenomenon was not observed in 3D SAMs, likely due
to the averaging of the transition dipole moment ofmolecules on spherical particles. The energy level of theπ*(C=O) peaks exceeded the binding energy of the C=O
peaks at 531.7 eV in the O 1s XPS spectra, indicatingthat it was suitable for subsequent resonant Auger
electron spectroscopy experiments.
We conducted time-of-flight mass spectrometry(TOF-MS) at Photon Factory BL-2B and utilized thedata obtained to construct near-edge X-ray absorption
mass spectra (NEXAMS), as shown in Figure 5. The
total ion yield (TIY) and partial ion yield (PIY) spectra
for both 2D and 3D SAMs exhibited a primary peaks
corresponding to σ*(O–CH3) at 288.9 eV. Thisobservation indicates that 3D SAMs form monolayers
similar to those formed by 2D SAMs. The presence of asingle sharp peak at 288.9 eV for CHn+ (n = 0–3) ionssuggests site-selective desorption of CHn+ ions from themethoxy group of SAMs [3].
Resonant Auger electron spectra (RAES) were
measured at HiSOR BL-13, and the charge transfer
times of the 2D and 3D SAMs were determined using
the core-hole-clock (CHC) approach. In Figure 6, RAES
at O 1s→π*(C=O) excitation is presented, with peaks
corresponding to spectator Auger decay processes
observed at ~486 eV and ~511 eV. The RAES at
π*(C=O) excitation was fitted with the RAES at postedge excitation and π*(C=O) excitation of 2D-aliphatic
SAMs, which exhibit insulation properties. Using thefitting coefficient and core hole lifetime of O 1s, thecharge transfer time for each 2D and 3D SAMs were
determined. The charge transfer time of 3D SAMs
decreased with increasing chain length, similar to that of
2D SAMs. Furthermore, the charge transfer time
between the 2D and 3D SAMs remained unchanged.
Our results suggest that the spectroscopic andelectrical properties of 3D SAMs closely resemble thoseof 2D SAMs. This similarity can be attributed to the factthat the AuNPs synthesized in our study had a diameterof ~7 nm, predominantly comprising {111} terraces on
their surfaces [4]. Notably, unique absorption features atthe corners and edges of the NPs were not observed in
the spectra. In essence, this study serves as a crucial link,extending the applicability of insights into the chargetransfer times obtained from diverse molecules observedin 2D to the context of 3D SAMs.

FIGURE 4. (a) Polarization dependence spectra of C
K-edge NEXAFS spectra of 2D and 3D-MP. (b) O Kedge NEXAFS spectra of 2D and 3D-MP.

FIGURE 5. C K-edge NEXAMS spectra of (a) 2DMP and (b) 3D-MP. Total ion yield spectra and partial
ion yield spectra of major products.

REFERENCES
1. M. Zharnikov, Acc. Chem. Res., 53, 2975–2984 (2020).
2. J. Stöhr, NEXAFS Spectroscopy, Surface Sciences, vol. 25,
Berlin, Springer,1992.
3. S. Wada, H. Kizaki, et al. J. Phys.: Condens. Matter, 18,
S1629-S1653 (2006).
4. A. C. Templeton, W. P. Wuelfing and R. W. Murray, Acc.
Chem. Res., 33, 27–36 (2000).

FIGURE 6. RAES of (a) MP and (b) MBP underπ*(C=O) excitation after Shirley backgroundsubtraction (dotted lines). The reproduced spectra(gray lines) were obtained by fitting with the normal
Auger spectra of each MP or MBP SAM (green lines)
and the spectator Auger spectra of 2D-aliphatic SAM(light blue lines).

P31

22BG044, 23BG033

BL-13

Ultrafast charge transfer through biphenyl and fluorene
monolayers studied by core-hole clock spectroscopy
Akinobu Niozua, Kakuto Yoshiokaa, Shogo Tendoa, Shohei Asakurab,
Yoshikazu Hanakib, Jumpei Koizumib, Yuri Ohurab, Junna Yamadab,and Shin-ichi Wadaa, caGraduate School of Science and Engineering, Hiroshima University,
Higashi-Hiroshima 739-8526, Japanb
Faculty of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japanc
Hiroshima Synchrotron Radiation Center, Hiroshima University,
Higashi-Hiroshima 739-0046, Japan
Keywords: Self-assembled monolayers, charge transfer, core-hole clock spectroscopy

Nanoscale charge transfer dynamics are crucial for fundamental physical chemistry and applications,such as nanoelectronics and photovoltaics. For these applications, it is crucial to understand the correlation
between the molecular structure and charge transport properties. Although molecular conductance has been
extensively studied using single-molecule conductance measurements [1], a notable disparity exists between
these fundamental investigations of single-molecule junctions and their direct application in functional
devices. The use of self-assembled monolayers (SAMs) is a potential solution to bridge this gap given theircapacity to form functional devices, thus connecting the insights gained from fundamental studies to practicalapplications.
TABLE 1.

Molecular structures and torsion angles of the molecules in SAMs.

Name

Structure

Torsion angle / °

MFL

0

MBP

0 [3]

MmBP

52

MdmBP

90

In this study, we investigated ultrafast charge transfer through self-assembled monolayers of biphenyl
and fluorene molecules via resonant Auger electron spectroscopy (RAES) using the core-hole clock (CHC)
technique [2]. In this approach, molecules are resonantly core-excited with soft X-rays, and the subsequent
electron transfer is probed by monitoring Auger decay spectra. The thiolated derivatives of biphenyl andfluorene used in this study are listed in Table 1. The addition of methyl groups induces torsion between thetwo phenyl rings within the SAMs, resulting in a reduction in π-conjugation. MBP molecules are anticipatedto adopt an almost planar conformation [3], similar to that observed in bulk solids. Conversely, the methylsubstituted thiolates (MmBP and MdmBP) are expected to exhibit twisted conformations owing to sterichindrance from the methyl groups. Density functional theory (DFT) calculations of the relaxed moleculargeometries yielded torsion angles of 52° and 90° for MmBP and MdmBP molecules, respectively. Thesemolecules have a methyl ester (COOCH3) moiety as the tail group, which serves as the site resonantly excitedwith soft X-rays in the CHC experiments.
The methylester-terminated biphenyl and fluorene derivatives were custom-synthesized by and purchasedfrom Tokyo Chemical Industry Co., Ltd. (for MFL, MmBP, and MdmBP) and NARD Institute Ltd. (forMBP). The SAMs were formed by immersing the Au substrates in 1 mM ethanol (for MBP, MmBP, and
MdmBP) and toluene (for MFL) solutions of the precursors at 30 ◦C for 24 h. After immersion, the SAM
samples were rinsed with solvent and dried under a flow of N2 gas. The SAM samples were characterizedusing near-edge X-ray fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS). NEXAFS,
XPS, and RAES experiments were conducted at HiSOR BL13. NEXAFS spectra were collected at the C andO K-edges using the total electron yield mode. The XPS and RAES spectra were acquired at an X-ray
incidence angle of 45° in the normal emission geometry using Omicron EA125 electron energy analyzer.
The C K-edge NEXAFS spectra showed several peaks corresponding to C 1s→ 𝜋 ∗ and C 1s→ 𝜎 ∗excitations. The polarization dependence of the 𝜋 ∗ intensities indicated the orientational order of themolecules within the SAMs. The S 2p XPS spectra of the target SAMs confirmed sulfur species chemisorbed
on Au. The NEXAFS and XPS spectra suggest the formation of ordered SAMs on the Au substrates.

FIGURE 1. RAES spectra of MFL, MBP, MmBP, and MdmBP SAMs. The spectra were compared with the pure resonant
spectrum recorded using the MHDA SAM and the normal Auger spectrum of the MBP SAM.

The RAES spectra at the O 1s→ 𝜋 ∗(C=O) excitation are shown in Fig. 1. The spectra were comparedwith the pure resonant spectrum recorded with an MHDA (HS-(CH2)15-COOCH3) SAM consisting of a long
aliphatic chain, which was assumed to show no charge transfer contribution. The spectra for the MFL, MBP,
and MmBP SAMs showed an increase in intensity corresponding to normal Auger decay, which indicatesultrafast charge transfer from the molecule to the Au substrate. For a quantitative analysis of the chargetransfer dynamics, the RAES spectra were fitted with linear combinations of the normal Auger spectrum andthe pure resonant Auger spectrum recorded with the MHDA SAM. The fitting analysis yielded chargetransfer times of 16, 16, ~47, and ≳50 fs for the MFL, MBP, MmBP, and MdmBP SAMs, respectively. The
CHC results demonstrate the conformational control of ultrafast charge transfer and suggest a negligible
influence of the methylene bridge on the charge transfer dynamics.

REFERENCES
1.
2.
3.

L. Venkataraman, J. E. Klare, C. Nuckolls, M. S. Hybertsen, and M. L. Steigerwald, Nature 442, 904-907 (2006).
M. Zharnikov, J. Electron Spectros. Relat. Phenomena 200, 160-173 (2015).
A. Masillamani et al., Chem. - A Eur. J. 18, 10335-10347 (2012).

P32

22BG042, 23BG034

BL-13

Soft X-ray Absorption Spectroscopy of Phospholipid Films
Supported on Au Substrates by Different Casting
Techniques
Yuri Ohuraa, Kakuto Yoshiokab, Shogo Tendob, Akinobu Niozua,b, and Shin-ichi
Wadaa,b,caaFaculty of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
Graduate School of Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japanc
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan

Keywords: Enter keywords. Linear polarization, XAS (X-ray absorption spectroscopy), NEXAFS (near edge X-ray absorption
fine structure), Spin-casting, Phospholipids, DPPC

Lipids are one of the major constituents of living organisms. In
particular, lipids self-assemble into oriented amphiphilic bilayers,which are the basic structure of the cell membranes. Lipid bilayers
not only play an important protective role in maintaining cells, butalso serve as sites for information transfer and protein reactions.
Therefore, understanding the properties of lipid membranes isfundamental to studying biological mechanisms in detail, and to thisend, attempts have been made to reproduce artificial cell membranes
by supporting lipids on metal substrates. Lipid membranes supported
on solid substrates (Figure 1), such as LB (Langmuir-Blodgett) andFIGURE 1. Molecular structure ofvesicle fusion methods, resemble natural cell membranes, and the
DPPC phospholipids and schematic
information obtained are known to be biologically reliable. We havebilayer membrane.
found that even a drop of an organic solution of phospholipid
molecules onto a gold substrate can form a highly oriented multi lipid-bilayers. In this study, we preparedmulti lipid-bilayer membranes by spin-casting method of lipid solutions, aiming to create more uniformly
oriented bilayers and to evaluate the state of the bilayers.
DPPC shown in Figure 1 was used as the phospholipid and dissolved in chloroform to make a lipid
solution. The solution was dropped onto Au substrates and dried under a nitrogen stream to create a multi
lipid-bilayer membranes. The spin-casting method was also used to create a more uniform bilayer films on
the substrates.
The prepared lipid films were characterized by NEXAFS (near edge X-ray absorption fine structure)measurements at HiSOR BL13 and AFM (atomic force microscopy) measurements at the laboratory.
NEXAFS spectra were obtained by irradiating soft X-rays in the carbon K-edge region, and the emitted
electrons were detected as drain current. The polarization angle dependence of the NEXAFS spectra wasmeasured by changing the incidence angle of horizontally polarized X-rays on the sample surface, and theorientation angle of the organized lipid molecules was thereby determined to evaluate the differences in themultilayer films due to the different preparation methods.
In this study, soft X-ray absorption spectroscopy measurements were performed at different incident
angles of soft X-rays to investigate the orientation angles of lipid films prepared by drop and spin-casting
methods. Figure 2 shows NEXAFS spectra in the C K-edge region measured at different sample positions
for lipid films prepared by drop and the spectrum for the lipid film prepared by spin-casting. The obtained
NEXAFS spectra show characteristic resonant excitation peaks at specific energies and different spectral
shapes with respect to the incident angle of soft X-ray. In other words, both lipid membranes are highlyoriented, despite being multilayered.

Each spectrum can be fitted with a Gaussian function to extract each resonant excitation component.
From the area intensities of fitted functions, the orientation angle of the transition dipole moment at eachtransition was determined. As a result, there is a clear difference between the orientation angles of the lipid
films prepared by the drop and spin-casting methods. This is thought to be due to the difference in the method
used to prepare the lipid films and the difference in the thickness of the films.
From the Rydberg and σ*(C-C) transitions, the orientation angle of the hydrocarbon chains, which
determines the overall shape of the lipid molecules, can be derived specifically. In lipid films prepared by
the spin-casting method, the orientation angle is closer to 55 degrees, which is called the "magic angle",than in films prepared by drop-casting. Based on previous studies [1], it is thought that the orientation
ordering is reduced in lipid films obtained by spin-casting due to the random structure of some of thehydrocarbon chains. In addition, the NEXAFS spectra of the lipid films obtained by spin-casting are different
from those obtained by the drop-casting method in their detailed shape, and are in good agreement with thespectral shape of the single bilayer films in the previous study [1]. These results suggest that the spin-casted
lipid films are sufficiently thin to be considered single bilayer films, unlike the drop method, and that thedegree of freedom of the molecules constituting the films is increased in this ultra-thin state.

REFERENCES
1. M. Tabuse, A. Niozu, and S. Wada, HiSOR Activity Report 2021, 100-101 (2022).

2.5

drop (center)

2.0
1.5
1.0
0.5

20
40
55
70
90

θ：

0.0
280

285

290

295

Intensity / arb.units

2.5

300

305

310

drop (edge)

2.0
1.5
1.0

FIGURE 3. Typical result of Gaussian fitting obtainedfor drop-casting film at 55-degree incidence angle.

0.5
0.0
280

285

290

295

2.5

300

305

310

spin-casting

2.0
1.5
1.0
0.5
0.0
280

285

290

295

300

305

310

Photon Energy / eV
FIGURE 2. Polarization dependent NEXAFS
spectra of (upper) center and (middle) edge positionsof DPPC drop-casting films and (c) spin-casting film
measured at C K-edge. θ: incident angle from thesurface, and therefore the angle of electric vector
from the surface normal.