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GeFujiwara, Hidenori*; Nakatani, Yasuhiro*; Aratani, Hidekazu*; Kanai-Nakata, Yuina*; Yamagami, Kohei*; Hamamoto, Satoru*; Kiss, Takayuki*; Sekiyama, Akira*; Tanaka, Arata*; Ebihara, Takao*; et al.
New Physics; Sae Mulli, 73(12), p.1062 - 1066, 2023/12
symmetry for anisotropic 
hybridization in the heavy-fermion superconductor CeNiGeFujiwara, Hidenori*; Nakatani, Yasuhiro*; Aratani, Hidekazu*; Kanai, Yuina*; Yamagami, Kohei*; Hamamoto, Satoru*; Kiss, Takayuki*; Yamasaki, Atsushi*; Higashiya, Atsushi*; Imada, Shin*; et al.
Physical Review B, 108(16), p.165121_1 - 165121_10, 2023/10
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)
-edge EXAFS and magnetic EXAFS studies on the halfmetallic ferromagnet CoMnSiKogo, Junya*; Fujiwara, Hidenori*; Sekiyama, Akira*; Saito, Yuji; Umetsu, Rie*; Niki, Kaori*
Journal of the Physical Society of Japan, 91(3), p.034702_1 - 034702_12, 2022/03
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)Fujiwara, Hidenori*; Umetsu, Rie*; Kuroda, Fumiaki*; Miyawaki, Jun*; Kashiuchi, Toshiyuki*; Nishimoto, Kohei*; Nagai, Kodai*; Sekiyama, Akira*; Irizawa, Akinori*; Takeda, Yukiharu; et al.
Scientific Reports (Internet), 11(1), p.18654_1 - 18654_9, 2021/09
Times Cited Count：0 Percentile：0(Multidisciplinary Sciences)
Sb
uncovered by soft X-ray magnetic circular dichroismSaito, Yuji; Fujiwara, Hidenori*; Yasui, Akira*; Kadono, Toshiharu*; Sugawara, Hitoshi*; Kikuchi, Daisuke*; Sato, Hideyuki*; Suga, Shigemasa*; Yamasaki, Atsushi*; Sekiyama, Akira*; et al.
Physical Review B, 102(16), p.165152_1 - 165152_8, 2020/10
Times Cited Count：1 Percentile：6.04(Materials Science, Multidisciplinary)Iwasaki, Toshiki*; Sekiyama, Tsuyoshi*; Nakajima, Teruyuki*; Watanabe, Akira*; Suzuki, Yasushi*; Kondo, Hiroaki*; Morino, Yu*; Terada, Hiroaki; Nagai, Haruyasu; Takigawa, Masayuki*; et al.
Atmospheric Environment, 214, p.116830_1 - 116830_11, 2019/10
Times Cited Count：6 Percentile：26.43(Environmental Sciences)The utilization of numerical atmospheric dispersion prediction (NDP) models for accidental discharge of radioactive substances was recommended by a working group of the Meteorological Society of Japan. This paper is to validate the recommendation through NDP model intercomparison in the accidental release from the Fukushima Dai-ichi Nuclear Power Plant in 2011. Emission intensity is assumed to be constant during the whole forecast period for the worst-case scenario unless time sequence of emission is available. We expect to utilize forecasts of surface air contaminations for preventions of inhalations of radioactive substances, and column-integrated amounts for mitigation of radiation exposure associated with wet deposition. Although NDP forecasts have ensemble spread, they commonly figure out relative risk in space and time. They are of great benefit to disseminating effective warnings to public without failure. The multi-model ensemble technique may be effective to improve the reliability.
symmetry in CeCuGe; Soft X-ray absorption and hard X-ray photoemission spectroscopyAratani, Hidekazu*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Kawada, Moeki*; Kanai, Yuina*; Yamagami, Kohei*; Fujioka, Shuhei*; Hamamoto, Satoru*; Kuga, Kentaro*; Kiss, Takayuki*; et al.
Physical Review B, 98(12), p.121113_1 - 121113_6, 2018/09
Times Cited Count：5 Percentile：25.82(Materials Science, Multidisciplinary)Ge in the normal stateNakatani, Yasuhiro*; Aratani, Hidekazu*; Fujiwara, Hidenori*; Mori, Takeo*; Tsuruta, Atsushi*; Tachibana, Shoichi*; Yamaguchi, Takashi*; Kiss, Takayuki*; Yamasaki, Atsushi*; Yasui, Akira*; et al.
Physical Review B, 97(11), p.115160_1 - 115160_7, 2018/03
Times Cited Count：5 Percentile：20.71(Materials Science, Multidisciplinary)VAl probed by soft X-ray spectroscopiesNagai, Kodai*; Fujiwara, Hidenori*; Aratani, Hidekazu*; Fujioka, Shuhei*; Yomosa, Hiroshi*; Nakatani, Yasuhiro*; Kiss, Takayuki*; Sekiyama, Akira*; Kuroda, Fumiaki*; Fujii, Hitoshi*; et al.
Physical Review B, 97(3), p.035143_1 - 035143_8, 2018/01
Times Cited Count：21 Percentile：70.17(Materials Science, Multidisciplinary)We have studied the electronic structure of ferrimagnetic MnVAl single crystals by means of soft X-ray absorption spectroscopy (XAS), X-ray absorption magnetic circular dichroism (XMCD), and resonant soft X-ray inelastic scattering (RIXS). We have successfully observed the XMCD signals for all the constituent elements. The Mn L XAS and XMCD spectra are reproduced by spectral simulations based on density-functional theory, indicating the itinerant character of the Mn 3
states. On the other hand, the V 3 electrons are rather localized since the ionic model can qualitatively explain the V L XAS and XMCD spectra. This picture is consistent with local 
excitations revealed by the V L
RIXS.
states in CeFe revealed by soft X-ray magnetic circular dichroismSaito, Yuji; Yasui, Akira*; Fuchimoto, Hiroto*; Nakatani, Yasuhiro*; Fujiwara, Hidenori*; Imada, Shin*; Narumi, Yasuo*; Kindo, Koichi*; Takahashi, Minoru*; Ebihara, Takao*; et al.
Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07
Times Cited Count：3 Percentile：17.1(Materials Science, Multidisciplinary)We revisit the delocalized character of the 4
states of CeFe
in the ferromagnetically ordered phase by X-ray magnetic circular dichroism (XMCD) in X-ray absorption spectroscopy (XAS) with improved data quality using single crystals. Surprisingly, the Ce 
XMCD spectral shape changes significantly as a function of temperature and applied magnetic field, with no concomitant changes in the spectral shape of the Ce XAS as well as the Fe 
XAS and XMCD. This unusual behavior is characterized by the 
states in a 4
configuration mixed into the 
ground state. Such extreme sensitivity of the Ce 4 states to the external perturbations can be related to the magnetic instability toward an antiferromagnetic phase in CeFe. Our experimental data presented here provide valuable insights into the underlying physics in strongly-hybridized ferromagnetic Ce compounds.
GeNakatani, Yasuhiro*; Fujiwara, Hidenori*; Aratani, Hidekazu*; Mori, Takeo*; Tachibana, Shoichi*; Yamaguchi, Takashi*; Kiss, Takayuki*; Yamasaki, Atsushi*; Yasui, Akira*; Yamagami, Hiroshi*; et al.
Journal of Electron Spectroscopy and Related Phenomena, 220, p.50 - 53, 2017/01
Times Cited Count：2 Percentile：17.1(Spectroscopy)We report the soft X-ray angle-resolved photoemission study for LaNiGe to reveal the electronic structures derived from non-4 bands of the heavy fermion compound CeNiGe. The photoemission spectra recorded at the La M
absorption edges clearly show the enhancement of the La 5 components in the valence band spectra. The circular dichroism of photoemission spectra reveals the band-dependent dichroic response due to the orbital symmetry.
; Soft X-ray absorption, magnetic circular dichroism, and angle-resolved photoemission spectroscopiesSaito, Yuji; Fujiwara, Hidenori*; Yamaguchi, Takashi*; Nakatani, Yasuhiro*; Mori, Takeo*; Fuchimoto, Hiroto*; Kiss, Takayuki*; Yasui, Akira*; Miyawaki, Jun*; Imada, Shin*; et al.
Journal of the Physical Society of Japan, 85(11), p.114713_1 - 114713_7, 2016/11
Times Cited Count：15 Percentile：68.09(Physics, Multidisciplinary)We report on the electronic structures of ferromagnetic CeAgSb using soft X-ray absorption (XAS), magnetic circular dichroism (XMCD), and angle-resolved photoemission (ARPES) spectroscopies. The Ce XAS spectra show very small satellite structures, reflecting a strongly localized character of the Ce 4 electrons. The linear dichroism effects in the Ce XAS spectra demonstrate the ground-state Ce 4 symmetry of 
, the spatial distribution of which is directed along the 
-axis. Nevertheless, ARPES spectra at the Ce 3-4 resonance show the momentum dependence of the intensity ratio between Ce 4
and 4
peaks in a part of the Brillouin zone, suggesting the non negligible momentum-dependent hybridization effect between the Ce 4 and the conduction electrons. This is associated with the moderate mass enhancement in CeAgSb.
Yamasaki, Atsushi*; Fujiwara, Hidenori*; Tachibana, Shoichi*; Iwasaki, Daisuke*; Higashino, Yuji*; Yoshimi, Chiaki*; Nakagawa, Koya*; Nakatani, Yasuhiro*; Yamagami, Kohei*; Aratani, Hidekazu*; et al.
Physical Review B, 94(11), p.115103_1 - 115103_10, 2016/11
Times Cited Count：17 Percentile：61.21(Materials Science, Multidisciplinary)In this study, we systematically investigate three-dimensional(3D) momentum-resolved electronic structures of Ruddlesden-Popper-type iridium oxides Sr
Ir
O
using soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES). Our results provide direct evidence of an insulator-to-metal transition that occurs upon increasing the dimensionality of the IrO-plane structure. This transition occurs when the spin-orbit-coupled 
= 1/2 band changes its behavior in the dispersion relation and moves across the Fermi energy. By scanning the photon energy over 350 eV, we reveal the 3D Fermi surface in SrIrO and 
-dependent oscillations of photoelectron intensity in SrIrO
. To corroborate the physics deduced using low-energy ARPES studies, we propose to utilize SX-ARPES as a powerful complementary technique, as this method surveys more than one whole Brillouin zone and provides a panoramic view of electronic structures.
-orbital symmetry of the ground state in Yb compounds by linear dichroism in core-level photoemissionMori, Takeo*; Kitayama, Satoshi*; Kanai, Yuina*; Naimen, Sho*; Fujiwara, Hidenori*; Higashiya, Atsushi*; Tamasaku, Kenji*; Tanaka, Arata*; Terashima, Kensei*; Imada, Shin*; et al.
Journal of the Physical Society of Japan, 83(12), p.123702_1 - 123702_5, 2014/12
Times Cited Count：16 Percentile：68.53(Physics, Multidisciplinary)We show that the strongly correlated 4-orbital symmetry of the ground state is revealed by linear dichroism in core-level photoemission spectra, as we have discovered for YbRhSi and YbCuSi. Theoretical analysis shows us that the linear dichroism reflects the anisotropic charge distributions resulting from a crystalline electric field. We have successfully determined the ground-state 4 symmetry for both compounds from the polarization-dependent angle resolved core-level spectra at a temperature well below the first excitation energy. The excited-state symmetry is also probed by temperature dependence of the linear dichroism where the high measurement temperatures are on the order of the crystal-field-splitting energies.
-space mapping of the electronic structure in an oxide-oxide interfaceBerner, G.*; Sing, M.*; Fujiwara, Hidenori*; Yasui, Akira*; Saito, Yuji; Yamasaki, Atsushi*; Nishitani, Yoshihito*; Sekiyama, Akira*; Pavlenko, N.*; Kopp, T.*; et al.
Physical Review Letters, 110(24), p.247601_1 - 247601_5, 2013/06
Times Cited Count：132 Percentile：96.58(Physics, Multidisciplinary)The interface between LaAlO and SrTiO hosts a two-dimensional electron system of itinerant carriers, although both oxides are band insulators. Interface ferromagnetism coexisting with superconductivity has been found and attributed to local moments. Experimentally, it has been established that Ti 3 electrons are confined to the interface. Using soft X-ray angle-resolved resonant photoelectron spectroscopy we have directly mapped the interface states in space. Our data demonstrate a charge dichotomy. A mobile fraction contributes to Fermi surface sheets, whereas a localized portion at higher binding energies is tentatively attributed to electrons trapped by O vacancies in the SrTiO.
Ge studied by soft X-ray angle-resolved photoemission spectroscopyYasui, Akira; Fujimori, Shinichi; Kawasaki, Ikuto; Okane, Tetsuo; Takeda, Yukiharu; Saito, Yuji; Yamagami, Hiroshi; Sekiyama, Akira*; Settai, Rikio*; Matsuda, Tatsuma; et al.
Physical Review B, 84(19), p.195121_1 - 195121_6, 2011/11
Times Cited Count：7 Percentile：32.89(Materials Science, Multidisciplinary)We have measured three-dimensional band structure and Fermi surfaces (FSs) of YbCuGe, which has recently become recognized as a nearly divalent Yb-based compound, by using soft X-ray angle-resolved photoemission spectroscopy. We clarified that the bands with finite Yb 4 contribution cross the Fermi level and are slightly involved in the formation of the FSs, in line with the valence-fluctuating state of YbCuGe. The obtained valence-band dispersions and the FSs are well explained by a relativistic band-structure calculation based on a local-density-approximation (LDA). These results suggest that the LDA calculation is a good starting point for understanding of the electronic state of YbCuGe as well as nearly divalent Yb-based compounds.
GeYasui, Akira; Fujimori, Shinichi; Kawasaki, Ikuto; Okane, Tetsuo; Takeda, Yukiharu; Saito, Yuji; Yamagami, Hiroshi; Sekiyama, Akira*; Settai, Rikio*; Matsuda, Tatsuma; et al.
Journal of Physics; Conference Series, 273, p.012067_1 - 012067_4, 2011/02
Times Cited Count：3 Percentile：62.76(Physics, Condensed Matter)Soft X-ray photoemission spectroscopies have been performed on YbCuGe, which is thought to be a Yb divalent system, to investigate its bulk electronic structure including Yb 4 electrons. Small but finite Yb
multiplet peaks were found at 6
12 eV in the angle-integrated spectrum, suggesting that it is a valence fluctuation compound. An "anti-crossing" Yb 4 bands with conduction bands were observed in the angle-resolved spectrum. This is the evidence that the Yb 4 electrons form a band state through the hybridization with Ge 4
and Cu 3 electrons.
)O (=Cr,Ti)Mo, S.-K.*; Kim, H.-D.*; Denlinger, J. D.*; Allen, J. W.*; Park, J.-H.*; Sekiyama, Akira*; Yamasaki, Atsushi*; Suga, Shigemasa*; Saito, Yuji; Muro, Takayuki*; et al.
Physical Review B, 74(16), p.165101_1 - 165101_12, 2006/10
Times Cited Count：49 Percentile：84.92(Materials Science, Multidisciplinary)We present high-resolution bulk-sensitive photoemission spectra of (V)O (=Cr,Ti). The measurements were made for the paramagnetic metal (PM), paramagnetic insulator (PI), and antiferromagnetic insulator (AFI) phases of (V)O. In the PM phase, we observe a prominent quasiparticle peak in general agreement with theory, which combines dynamical mean-field theory with the local density approximation. For both the PI and AFI phases, the vanadium 3 parts of the valence spectra are not simple one peak structures. For the PI phase, there is not yet a good theoretical understanding of these structures. Spectra taken in the same phases with different compositions show interesting monotonic changes as the dopant concentration increases, regardless of the dopant species. With increased Cr-doping, the AFI phase gap decreases and the PI phase gap increases.
ReOIrizawa, Akinori*; Higashiya, Atsushi*; Kasai, Shuichi*; Sasabayashi, Takehisa*; Shigemoto, Akihiko*; Sekiyama, Akira*; Imada, Shin*; Suga, Shigemasa*; Sakai, Hironori; Ono, Hiroyuki*; et al.
Journal of the Physical Society of Japan, 75(9), p.094701_1 - 094701_5, 2006/09
Times Cited Count：6 Percentile：41.83(Physics, Multidisciplinary)Photoemission spectroscopy (PES) and O 
X-ray absorption spectroscopy (XAS) measurements have been performed for Cd Re O
single crystals. Temperature variations of their spectra reveal that the phase transition at 120 K directly changes the band structure near the Fermi level compared with another transition near 200 K. The roles of the transitions are discussed in terms of the changes in the Re-O orbital hybridization.
Sato, Hitoshi*; Yoshikawa, Kunta*; Hiraoka, Koichi*; Arita, Masashi*; Fujimoto, Koji*; Kojima, Kenichi*; Muro, Takayuki*; Saito, Yuji; Sekiyama, Akira*; Suga, Shigemasa*; et al.
Physical Review B, 69(16), p.165101_1 - 165101_6, 2004/04
Times Cited Count：33 Percentile：77.9(Materials Science, Multidisciplinary)no abstracts in English
