Mizokawa group

Department of Applied Physics

School of Advanced Science and Engineering

Waseda University

Members:

P Takashi Mizokawa mizokawa at waseda.jp

R Kou Takubo

M2 Manato Yamaguchi

M1 Masashi Kawakatsu

M1 Shota Kuribayashi

M1 Ryuki Matsuhashi

M1 Joe Mineo

B4 Kazuki Kumitake

B4 Toru Kobayashi

B4 Shota Hayashida

B4 Yuki Midorikawa

B4 Shota Yamamoto

Address: 55N-309, Nishiwaseda campus, Waseda University

3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan

Sapienza-TMU-Waseda workshop: March 17, 2025

https://sites.google.com/view/sapienza-tmu-waseda-workshop/home

70 years of Tanabe-Sugano diagrams: September 10-12, 2024

https://sites.google.com/view/70years-of-tanabe-sugano/home

JPSJ special topics

Selected papers:

V and Se spectral reconstruction by charge density wave formation in VSe₂ probed by angle-resolved photoemission spectroscopy,

K. Fujinuma, T. Hara, M. Emi, N. Katayama, H. Sawa, X. Zhao, K. Takubo, G. Tomassucci, F. Minati, A. Barinov, K. Ozawa, N. L. Saini, T. Mizokawa,

Physical Review B 113, 235112 (2026).

4s Molecular Orbitals and Strongly Correlated 3d States in TiO_x and VO_x,

Daisuke Takegami, Anna Melendez-Sans, Takashi Miyoshino, Ryo Nakamura, Miguel Ferreira-Carvalho, Georg Poelchen, Chun-Fu Chang, Masato Yoshimura, Ku-Ding Tsuei, Haruka Matsumoto, Asuka Yanagida, Ryota Yoshimura, Suguru Yano, Takumi Iwata, Takuro Katsufuji, Atsushi Hariki, Liu Hao Tjeng, Takashi Mizokawa,

Journal of the American Chemical Society 148, 16821-16829 (2026).

Impact of S substitution for Se on the photoinduced insulator-to-metal transition in an excitonic insulator Ta₂NiSe₅,

Masaki Hattori, Mario Okawa, Takeshi Suzuki, Yu Takahashi, Yangfan Lu, Hedenori Takagi, Yigui Zhong, Kecheng Liu, Teruto Kanai, Jiro Itatani, Shik Shin, Kozo Okazaki, Takashi Mizokawa,

Discover Physics 2, 3 (2026).

Yb 4f-Ta 5d Hybridization and Valence Evolution in Tetragonal Tungsten Bronze Ba_3−xYb_xTa₅O₁₅,

Daisuke Takegami, Haruki Takei, Masato Yoshimura, Takuro Katsufuji, Takashi Mizokawa,

Journal of the Physical Society of Japan 95, 024708 (2026).

Possible Altermagnetic Band Splitting in a Fe Spin Ladder System: Angle-Resolved Photoemission Spectroscopy on BaFe₂S₃,

Shun Iwasaki, Kou Takubo, Shinnosuke Takaya, Masashi Arita, Kazuki Hashizume, Takuya Aoyama, Kenya Ohgushi, Naurang L Saini, Takashi Mizokawa,

Journal of the Physical Society of Japan 94, 123704 (2025). Selected as JPS Hot topics

Dirac-like band dispersion at the pyrite-type (100) surface revealed by soft x-ray angle-resolved photoemission spectroscopy,

K. Fujinuma, D. Takegami, H. Honda, D. Shiga, H. Kumigashira, R. Higashinaka, T. D. Matsuda, Y. Aoki, M. Hedo, Y. Ōnuki, N. L. Saini, T. Mizokawa,

Physical Review B 112, 205416 (2025).

Circular Dichroism in Resonant Inelastic X-Ray Scattering: Probing Altermagnetic Domains in MnTe,

D. Takegami, T. Aoyama, T. Okauchi, T. Yamaguchi, S. Tippireddy, S. Agrestini, M. García-Fernández, T. Mizokawa, K. Ohgushi, Ke-Jin Zhou, J. Chaloupka, J. Kuneš, A. Hariki, H. Suzuki,

Physical Review Letters 135, 196502 (2025).

Impact of X-Ray Irradiation on the Bi Valence of MA₃Bi₂I₉ and Cs₃Bi₂I₉,

Keita Saito, Takuya Tsunoda, Naurang Lal Saini, Takashi Mizokawa,

The Journal of Physical Chemistry C 129, 17998-18003 (2025).

Effect of S Substitution for Se on the Ta–Ni Hybridization in an Excitonic Insulator Ta₂NiSe₅,

Masaki Hattori, Mario Okawa, Kenichi Ozawa, Yangfan Lu, Hidenori Takagi, Naurang L Saini, Takashi Mizokawa,

Journal of the Physical Society of Japan 94, 094709 (2025).

Electronic inhomogeneity in Cs- and Sb-terminated surfaces of CsV₃Sb₅ probed by scanning photoemission spectromicroscopy,

T. Mizokawa, G. Tomassucci, M. Hattori, F. Minati, L. Tortora, A. Barinov, Z. Wang, J.-X. Yin, N. L. Saini,

Physical Review B 112, 075106 (2025).

Pb and Bi Mixed Valence States Induced by X-ray Irradiation in MAPbI₃ and MAPb_0.9Bi_0.1I₃,

Keita Saito, Rinka Iguchi, Ryota Muneda, Naurang Lal Saini, Takashi Mizokawa,

ACS Applied Energy Materials 8, 9544-9550 (2025).

Valence, charge transfer, and orbital-dependent correlation in bilayer nickelates Nd₃Ni₂O₇,

Daisuke Takegami, Takaki Okauchi, Edgar Abarca Morales, Koto Fujinuma, Mizuki Furo, Masato Yoshimura, Ku-Ding Tsuei, Grace A. Pan, Dan Ferenc Segedin, Qi Song, Hanjong Paik, Charles M. Brooks, Julia A. Mundy, Takashi Mizokawa, Liu Hao Tjeng, Berit H. Goodge, and Atsushi Hariki,

Physical Review B 111, 165101 (2025).

Effect of S and Se holes on charge fluctuations in pyrite-type and revealed by hard x-ray photoemission spectroscopy,

K. Fujinuma, D. Takegami, A. Melendez-Sans, M. Yoshimura, K.-D. Tsuei, R. Higashinaka, T. D. Matsuda, Y. Aoki, M. Hedo, Y. Ōnuki, L. H. Tjeng, and T. Mizokawa,

Physical Review B 111, 115147 (2025).

Beyond a cluster-Mott state in the breathing kagome lattice of LiZn₂Mo₃O₈,

S. V. Streltsov, D. Takegami, R. Nakamura, P. P. Kovaleva, A. I. Poteryaev, S. A. Nikolaev, H.-H. Xu, Y. Sui, M. Yoshimura, K.-D. Tsuei, N. L. Saini, D. I. Khomskii, and T. Mizokawa,

Physical Review B 111, 085124 (2025).

Bulk Mott gap and S 3𝑠/3𝑝 spectral distribution in pyrite-type NiS₂ revealed by hard x-ray photoemission spectroscopy,

K. Fujinuma, D. Takegami, T. Higo, A. Melendez-Sans, G. Poelchen, M. Yoshimura, K.-D. Tsuei, S. Nakatsuji, L. H. Tjeng, and T. Mizokawa,

Physical Review B 110, 125136 (2024).

Observation of an Electron Pocket Around Time-Reversal Invariant L Point in Chiral α-RhSn4 by Means of Nano-ARPES,

Genki Hayashi, Masaki Hattori, Naoki Nakamura, Ryuji Higashinaka, Tatsuma D. Matsuda, Yuji Aoki, Marek Kopciuszynski, Alexey Barinov, Naurang L. Saini, and Takashi Mizokawa,

Journal of the Physical Society of Japan 93, 094706 (2024).

Charge Disproportionation for Trimerization and Tetramerization in Spinel-Type AlV₂O₄,

Mario Okawa, Ryota Shimoyama, Ryohei Takayanagi, Akira Yasui, Eiji Ikenaga, Takuro Katsufuji, Tomohiko Saitoh, and Takashi Mizokawa,

Journal of the Physical Society of Japan 93, 074709 (2024). Selected as JPS Hot topics

Negative charge-transfer energy in SrFeO₃ revisited with hard x-ray photoemission spectroscopy,

D. Takegami, M. Nakamura, A. Melendez-Sans, K. Fujinuma, R. Nakamura, M. Yoshimura, K.-D. Tsuei, A. Tanaka, M. Gen, Y. Tokunaga, S. Ishiwata, and T. Mizokawa,

Physical Review B 109, 235138 (2024).

Valence study of Li(Ni_0.5Mn_0.5)_1−𝑥Co_𝑥O₂ and LiNi_1−𝑥Co_𝑥O₂: The role of charge transfer and charge disproportionation,

Daisuke Takegami, Kosuke Kawai, Miguel Ferreira-Carvalho, Sahana Rößler, Cheng-En Liu, Chang-Yang Kuo, Chun-Fu Chang, Atsusa Minamida, Tatsuya Miyazaki, Masashi Okubo, Liu Hao Tjeng, and Takashi Mizokawa,

Physical Review Materials 8, 055401 (2024).

Interplay between strongly localized Eu 4𝑓 and weakly localized Nb 4𝑑 electrons in Eu₃Nb₅O₁₅,

R. Nakamura, D. Takegami, A. Melendez-Sans, L. H. Tjeng, T. Miyoshino, K. Iwamoto, W. Sekino, M. Yoshimura, K.-D. Tsuei, T. Katsufuji, and T. Mizokawa,

Physical Review B 109, 165148 (2024).

Bulk electronic structure of 𝐴V₃Sb₅ (𝐴=K, Cs) studied by hard x-ray photoemission spectroscopy: Possibility of bond order without charge disproportionation,

D. Takegami, K. Fujinuma, R. Nakamura, M. Yoshimura, K.-D. Tsuei, N. L. Saini, Zhiwei Wang, Jia-Xin Yin, and T. Mizokawa,

Physical Review B 109, 155108 (2024).

Absence of Ni²⁺/Ni³⁺ charge disproportionation and possible roles of O 2𝑝 holes in La₃Ni₂O_7−𝛿 revealed by hard x-ray photoemission spectroscopy,

D. Takegami, K. Fujinuma, R. Nakamura, M. Yoshimura, K.-D. Tsuei, G. Wang, N. N. Wang, J.-G. Cheng, Y. Uwatoko, and T. Mizokawa,

Physical Review B 109, 125119 (2024).

Electronic Properties of Chiral IrGe₄ Studied by Angle Resolved Photoemission Spectroscopy and Band Structure Calculation,

Genki Hayashi, Taiki Shimaiwa, Mario Okawa, Naoki Nakamura, Ryuji Higashinaka, Tatsuma D. Matsuda, Yuji Aoki, Miho Kitamura, Daisuke Shiga, Hiroshi Kumigashira, Marek Kopciuszynski, Alexey Barinov, Naurang. L. Saini, and Takashi Mizokawa,

Journal of the Physical Society of Japan 93, 014702 (2024).

Linear dichroic x-ray absorption response of Ti-Ti dimers along the 𝑐 axis in Ti₂O₃ upon Mg substitution,

M. Okawa, D. Takegami, D. S. Christovam, M. Ferreira-Carvalho, C.-Y. Kuo, C. T. Chen, T. Miyoshino, K. Takasu, T. Okuda, C. F. Chang, L. H. Tjeng, and T. Mizokawa,

Physical Review B 108, 195108 (2023).

Temporal Evolution and Fluence Dependence of Band Structure in Photoexcited Ta₂Ni_0.9Co_0.1Se₅ Probed by Time- and Angle-Resolved Photoemission Spectroscopy,

Yu Takahashi, Takeshi Suzuki, Masaki Hattori, Mario Okawa, Hidenori Takagi, Naoyuki Katayama, Hiroshi Sawa, Minoru Nohara, Yigui Zhong, Kecheng Liu, Teruto Kanai, Jiro Itatani, Shik Shin, Kozo Okazaki, and Takashi Mizokawa,

Journal of the Physical Society of Japan 92, 064706 (2023). Selected as JPS Hot topics

Robustness of Excitonic Coupling in Ta₂NiSe₅ Against Electronic Inhomogeneity Introduced by S Substitution for Se,

Masaki Hattori, Giovanni Tomassucci, Genki Hayashi, Mario Okawa, Marek Kopciuszynski, Alexey Barinov, Yangfan Lu, Hidenori Takagi, Naurang L. Saini, and Takashi Mizokawa,

Advanced Quantum Technologies 6, 2300034 (2023).

Intra 𝑐-axis dimer hybridization and mixed valency in Mg-doped Ti₂O₃,

T. Miyoshino, D. Takegami, A. Meléndez-Sans, R. Nakamura, M. Yoshimura, K.-D. Tsuei, K. Takasu, T. Okuda, L. H. Tjeng, and T. Mizokawa,

Physical Review B 107, 115145 (2023).

Quasi One-Dimensional Band Structure of Photoinduced Semimetal Phase of Ta₂Ni_1−xCo_xSe₅ (x = 0.0 and 0.1),

Takumi Mitsuoka, Yu Takahashi, Takeshi Suzuki, Mario Okawa, Hidenori Takagi, Naoyuki Katayama, Hiroshi Sawa, Minoru Nohara, Mari Watanabe, Jiadi Xu, Qianhui Ren, Masami Fujisawa, Teruto Kanai, Jiro Itatani, Kozo Okazaki, Shik Shin, and Takashi Mizokawa,

Journal of the Physical Society of Japan 92, 023703 (2023).

Effect of Oxygen Hole in Li₂MnO₃ Revealed by Hard X-ray Photoemission Spectroscopy and Band Structure Calculations,

Keisuke Morita, Mitoki Itoda, Eiji Hosono, Daisuke Asakura, Masashi Okubo, Yasumasa Takagi, Akira Yasui, Naurang L. Saini, and Takashi Mizokawa,

Journal of the Physical Society of Japan 92, 014702 (2023).

Direct observation of multiple conduction-band minima in high-performance thermoelectric SnSe,

Mario Okawa, Yuka Akabane, Mizuki Maeda, Gangjian Tan, Li-Dong Zhao, Mercouri G. Kanatzidis, Takeshi Suzuki, Mari Watanabe, Jiadi Xu, Qianhui Ren, Masami Fujisawa, Teruto Kanai, Jiro Itatani, Shik Shin, Kozo Okazaki, Naurang L. Saini, Takashi Mizokawa,

Scripta Materialia 223, 115081 (2023).

Ti 3d Electronic States of Hollandite-type Ba_xTi₈O_16+δ Studied by Cluster-Model and Band-Structure Calculations,

Takashi Miyoshino, Ryo Nakamura, Naurang L. Saini, and Takashi Mizokawa,

Journal of the Physical Society of Japan 91, 124710 (2022).

Fermi Surface Geometry of Heavily Hole Doped CaKFe₄As₄ Revealed by Angle-Resolved Photoemission Spectroscopy,

Souma Hikami, Shigeyuki Ishida, Akira Iyo, Hiroshi Eisaki, Masashi Arita, Shiv Kumar, Eike F. Schwier, Kennya Shimada, Naurang L. Saini, and Takashi Mizokawa,

Journal of the Physical Society of Japan 91, 124704 (2022).

Electronic structure reconstruction by trimer formation in CsW₂O₆ studied by x-ray photoelectron spectroscopy,

R. Nakamura, D. Takegami, A. Melendez-Sans, L. H. Tjeng, M. Okawa, T. Miyoshino, N. L. Saini, M. Kitamura, D. Shiga, H. Kumigashira, M. Yoshimura, K.-D. Tsuei, Y. Okamoto, and T. Mizokawa,

Physical Review B 106, 195104 (2022).

Orbital dependent band degeneracy and edge states in single layer and AA bilayer honeycomb lattice systems with p orbital degeneracy,

Genki Hayashi1 and Takashi Mizokawa,

Journal of Physics Communications 6, 085011 (2022).

Domain Dependent Fermi Arcs Observed in a Striped Phase Dichalcogenide,

Takashi Mizokawa, Alexei Barinov, Viktor Kandyba, Alessio Giampietri, Ryoya Matsumoto, Yohei Okamoto, Kou Takubo, Koji Miyamoto, Taichi Okuda, Sunseng Pyon, Hiroyuki Ishii, Kazutaka Kudo, Minoru Nohara, and Naurang L. Saini,

Advanced Quantum Technologies 5, 2200029 (2022).

Bulk and surface electronic structure of MnPSe₃ revealed by photoemission and x-ray absorption spectroscopy,

Masato Fujii, Tomoyuki Yamaguchi, Takuo Ohkochi, Chandan De, Sang-Wook Cheong, and Takashi Mizokawa,

Physical Review B 106, 035118 (2022).

Electronic Structure of Spinel-Type MgTi₂O₄: Valence Change at Surface and Effect of Fe Substitution for Mg,

Tomoyuki Yamaguchi, Mario Okawa, Hiroki Wadati, Tom Z. Regier, Tom Saitoh, Yasumasa Takagi, Akira Yasui, Masahiko Isobe, Yutaka Ueda, and Takashi Mizokawa,

Journal of the Physical Society of Japan 91, 074704 (2022).

Impact of Co or Cu Substitution for Ni on the Electronic Structure of Ta₂NiSe₅ Studied by Band Structure Calculations,

Yu Takahashi, and Takashi Mizokawa,

Journal of the Physical Society of Japan 91, 074714 (2022).

Electronic Structure of Ba₃Nb₅O₁₅ and Ba₂SrNb₅O₁₅ Studied by Band Calculation and Photoemission Spectroscopy,

Ryo Nakamura, Takashi Miyoshino, Yuhki Kondoh, Tomomasa Kajita, Takuro Katsufuji, Naurang L. Saini, and Takashi Mizokawa,

Journal of the Physical Society of Japan 91, 064711 (2022).

Surface Electronic States and Inclining Surfaces in MoTe₂ Probed by Photoemission Spectromicroscopy,

Ryoya Matsumoto, Naurang L. Saini, Alessio Giampietri, Viktor Kandyba, Alexey Barinov, Rajveer Jha, Ryuji Higashinaka, Tatsuma D. Matsuda, Yuji Aoki, and Takashi Mizokawa,

Journal of the Physical Society of Japan 90, 084704 (2021).

Fermi Surface Geometry and Inhomogeneous Electronic States in Pr_1.3−xLa_0.7Ce_xCuO₄ (x = 0.05) with Small Superconducting Volume Fraction,

Yu Matsuzawa, Tomohiro Morita, Masashi Arita, Alessio Giampietri, Viktor Kandyba, Alexey Barinov, Akira Takahashi, Yusuke Nagakubo, Tadashi Adachi, Yoji Koike, Atsushi Fujimori, Naurang L. Saini, and Takashi Mizokawa,

Journal of the Physical Society of Japan 90, 054704 (2021).

Evolution of the Fermi surface in superconductor PrO_1-xF_xBiS₂ (x=0.0, 0.3, and 0.5) revealed by angle-resolved photoemission spectroscopy,

T. Morita, Y. Matsuzawa, S. Kumar, E. F. Schwier, K. Shimada, R. Higashinaka, T. D. Matsuda, Y. Aoki, N. L. Saini, and T. Mizokawa,

Physical Review B 103, 094510 (2021).

Interplay between electronic correlation and atomic disorder in a low carrier density 4d transition-metal oxide,

T. Yasuda, Y. Kondo, T. Kajita, K. Murota, D. Ootsuki, Y. Takagi, A. Yasui, N. L. Saini, T. Katsufuji, and T. Mizokawa,

Physical Review B 102, 205133 (2020).

Photoinduced Phase Transition from Excitonic Insulator to Semimetal-like State in Ta₂Ni_1−xCo_xSe₅ (x = 0.10),

Takumi Mitsuoka, Takeshi Suzuki, Hidenori Takagi, Naoyuki Katayama, Hiroshi Sawa, Minoru Nohara, Mari Watanabe,

Jiadi Xu, Qianhui Ren, Masami Fujisawa, Teruto Kanai, Jiro Itatani, Shik Shin, Kozo Okazaki, and Takashi Mizokawa,

Journal of the Physical Society of Japan 89, 124703 (2020).

Momentum Dependent Band Renormalization and Surface Aging Effect on a Zone Center Electron Pocket

in NaSn₂As₂ Revealed by Angle-Resolved Photoemission Spectroscopy,

Yuka Akabane, Taiki Shimaiwa, Yosuke Goto, Yoshikazu Mizuguchi, Takayoshi Yokoya, Masashi Arita, Shiv Kumar,

Eike F. Schwier, Kenya Shimada, Naurang L. Saini, and Takashi Mizokawa,

Journal of the Physical Society of Japan 89, 114707 (2020).

Charge correlation in V₂OPO₄ probed by hard x-ray photoemission spectroscopy,

Kota Murota, Elise Pachoud, J. Paul Attfield, Robert Glaum, Tatsunori Yasuda, Daiki Ootsuki,

Yasumasa Takagi, Akira Yasui, Daniel I. Khomskii, and Takashi Mizokawa,

Physical Review B 101, 235159 (2020).

Vanadium 3d charge and orbital states in V₂OPO₄ probed by x-ray absorption spectroscopy,

Kota Murota, Elise Pachoud, J. Paul Attfield, Robert Glaum, Ronny Sutarto, Kou Takubo, Daniel I. Khomskii, and Takashi Mizokawa,

Physical Review B 101, 245106 (2020).

Temperature-dependent evolution of Ti 3d spectral features at surface of Ba_xTi₈O_16+δ,

S. Dash, H. Enomoto, T. Kajita, K. Ono, K. Horiba, M. Kobayashi, H. Kumigashira, V. Kandyba, A. Giampietri, A. Barinov, F. Stramaglia, N. L. Saini, T. Katsufuji, and T. Mizokawa,

Physical Review B 100, 125153 (2019).

Inhomogeneous charge distribution in a self-doped EuFBiS₂ superconductor,

T. Sugimoto, E. Paris, K. Terashima, A. Barinov, A. Giampietri, T. Wakita, T. Yokoya, J. Kajitani, R. Higashinaka, T. D. Matsuda, Y. Aoki, T. Mizokawa, and N. L. Saini,

Physical Review B 100, 064520 (2019).

Temperature-dependent valence state within the metallic phase of BaV₁₀O₁₅ probed by hard x-ray photoelectron spectroscopy,

S. Dash, M. Okawa, T. Kajita, T. Yoshino, R. Shimoyama, K. Takahashi, Y. Takahashi, R. Takayanagi, T. Saitoh, A. Yasui, E. Ikenaga, N. L. Saini, T. Katsufuji, and T. Mizokawa,

Physical Review B 99, 035122 (2019).

Orbital-dependent band renormalization in WTe₂ revealed by angle-resolved photoemission spectroscopy,

R. Matsumoto, T. Sugimoto, T. Mizokawa, N. L. Saini, M. Arita, R. Jha, R. Higashinaka, T. D. Matsuda, and Y. Aoki,

Physical Review B 98, 205138 (2018).

Impact of valence fluctuations on the electronic properties of RO_1−xF_xBiS₂,

S. Dash, T. Morita, K. Kurokawa, Y. Matsuzawa, N. L. Saini, N. Yamamoto, Joe Kajitani, R. Higashinaka, T. D. Matsuda, Y. Aoki, and T. Mizokawa,

Physical Review B 98, 144501 (2018).

Anomalous metallic state with strong charge fluctuations in Ba_xTi₈O_16+δ revealed by hard x-ray photoemission spectroscopy,

S. Dash, T. Kajita, M. Okawa, T. Saitoh, E. Ikenaga, N. L. Saini, T. Katsufuji, and T. Mizokawa,

Physical Review B 97, 165116 (2018).

Unusually large chemical potential shift in a degenerate semiconductor: Angle-resolved photoemission study of SnSe and Na-doped SnSe,

M. Maeda, K. Yamamoto, T. Mizokawa, N. L. Saini, M. Arita, H. Namatame, M. Taniguchi, G. Tan, L. D. Zhao, and M. G. Kanatzidis,

Physical Review B 97, 121110(R) (2018).

Inhomogeneous electronic states associated with charge-orbital order/disorder in BaV₁₀O₁₅ probed by photoemission spectromicroscopy,

T. Yoshino, K. Wakita, E. Paris, A. Barinov, T. Kajita, T. Katsufuji, V. Kandyba, T. Sugimoto, T. Yokoya, N. L. Saini, and T. Mizokawa,

Physical Review B 96, 115161 (2017).

Orbital order and fluctuations in the two-leg ladder materials BaFe₂X₃ (X=S and Se) and CsFe₂Se₃,

Kou Takubo, Yuichi Yokoyama, Hiroki Wadati, Shun Iwasaki, Takashi Mizokawa, Teak Boyko, Ronny Sutarto, Feizhou He, Kazuki Hashizume, Satoshi Imaizumi, Takuya Aoyama, Yoshinori Imai, and Kenya Ohgushi,

Physical Review B 96, 115157 (2017).

Electronic structure and polar catastrophe at the surface of Li_xCoO₂ studied by angle-resolved photoemission spectroscopy,

Y. Okamoto, R. Matsumoto, T. Yagihara, C. Iwai, K. Miyoshi, J. Takeuchi, K. Horiba, M. Kobayashi, K. Ono, H. Kumigashira, N. L. Saini, and T. Mizokawa,

Physical Review B 96, 125147 (2017).

previous papers (2004-2014)

research projects

Photoemission spectroscopy and inverse-photoemission spectroscopy:

Photoelectrons are emitted from solid surfaces on which ultraviolet or x-ray light is shone.

By measuring the energy and momentum of the photoelectrons, we can study occupied states of the solid (photoemission spectroscopy). On the other hand, we can study unoccupied states of the solid by detecting light emitted from surfaces of the solid on which electrons are shone (inverse-photoemission spectroscopy).

We have been developing a high-energy-resolution inverse-photoemission system based on dispersion matching of light and electron. Using the photoemission and inverse-photoemission experiments, we have been studying the electronic structure of bulk and surface of various solids.

In particular, we are interested in transition-metal compounds that show rich physical properties such as ferromagnetism, superconductivity, valence transition, and metal-insulator transition. In transition-metal compounds, d-electrons with spin, charge and orbital degrees of freedom are affected by complicated lattice distortions, and show interesting electric and magnetic properties. We have been studying the relationship between the physical properties and electronic structure of transition-metal compounds using experimental methods such as photoemission and inverse-photoemission spectroscopy and theoretical methods such as unrestricted Hartree-Fock calculation.

As for new aspects of transition-metal compounds, an interesting question is what kind of new electronic states are realized when d-electrons are confined at solid surface/interface. Another interesting question is how confined d-electrons behave when perturbed by photons. We are trying to answer these questions by studying thin films and nano particles of various transition-metal compounds under laser illumination. Hopefully, the research projects along this line would contribute to development of new optical and energy devices.

Figure：Dispersion matching for inverse-photoemission spectroscopy