**Mizokawa group**

Department of Applied Physics

School of Advanced Science and Engineering

Waseda University

Members:

P Takashi Mizokawa mizokawa at waseda.jp

L Mario
Okawa

M2 Yu
Takahashi

M2 Genki Hayashi

M2 Takashi
Miyoshino

M2 Keisuke
Morita

M1 Keita
Saito

M1 Shinnosuke
Takaya

M1 Masaki
Hattori

M1 Ryo
Nakamura

B4 Rinka Iguchi

B4 Atsuhiro Nonaka

B4 Kakeru Hiroki

B4 Hiroki
Honda

B4 Ryota Muneda

B4 Yotaro Yamamoto

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

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

Selected papers:

**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 _{x}Ti_{8}O_{16+δ}
Studied by Cluster-Model and Band-Structure Calculations,**

**Takashi
Miyoshino, Ryo Nakamura, Naurang
L. Saini, and Takashi Mizokawa, J. Phys. Soc. Jpn.
91, 124710 (2022).**

**Fermi Surface Geometry of Heavily Hole Doped
CaKFe _{4}As_{4} 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, J. Phys. Soc. Jpn. 91, 124704 (2022).**

**Electronic
structure reconstruction by trimer formation in CsW _{2}O_{6}
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,
Phys. Rev. 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, J. Phys. Commun. 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,**

**Adv.
Quantum Technol. 5, 2200029 (2022).**

**Bulk
and surface electronic structure of MnPSe _{3} revealed by photoemission
and x-ray absorption spectroscopy,**

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

**Phys.
Rev. B 106, 035118 (2022).**

**Electronic Structure of
Spinel-Type MgTi _{2}O_{4}: 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,**

**J. Phys. Soc. Jpn. 91, 074704 (2022).**

**Impact
of Co or Cu Substitution for Ni on the Electronic Structure of Ta _{2}NiSe_{5}
Studied by Band Structure Calculations,**

**Yu
Takahashi, and Takashi Mizokawa,**

**J.
Phys. Soc. Jpn. 91, 074714 (2022).**

**Electronic
Structure of Ba _{3}Nb_{5}O_{15} and Ba_{2}SrNb_{5}O_{15}
Studied by Band Calculation and Photoemission Spectroscopy,**

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

**J.
Phys. Soc. Jpn. 91, 064711 (2022).**

**Surface
Electronic States and Inclining Surfaces in MoTe _{2} 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,**

**J.
Phys. Soc. Jpn. 90, 084704 (2021).**

**Fermi
Surface Geometry and Inhomogeneous Electronic States in Pr _{1.3−x}La_{0.7}Ce_{x}CuO_{4}
(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,**

**J.
Phys. Soc. Jpn. 90, 054704 (2021).**

**Evolution of the Fermi surface in
superconductor PrO _{1-x}F_{x}BiS_{2} (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,**

**Phys. Rev. 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,**

**Phys. Rev. B 102, 205133 (2020).**

**Photoinduced Phase Transition from
Excitonic Insulator to Semimetal-like State in Ta _{2}Ni_{1−x}Co_{x}Se_{5}
(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, **

**J. Phys. Soc. Jpn.
89, 124703 (2020).**

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

**in NaSn _{2}As_{2} 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,**

**J. Phys. Soc. Jpn.
89, 114707 (2020).**

**Charge correlation in V _{2}OPO_{4}
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,**

**Phys. Rev. B 101, 235159 (2020).**

**Vanadium 3d charge and orbital states in V _{2}OPO_{4}
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, **

**Phys. Rev. B 101, 245106 (2020).**

**Temperature-dependent
evolution of Ti 3d spectral features at surface of Ba _{x}Ti_{8}O_{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,**

**Phys.
Rev. B 100, 125153 (2019).**

**Inhomogeneous
charge distribution in a self-doped EuFBiS _{2} 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,**

**Phys.
Rev. B 100, 064520 (2019).**

**Temperature-dependent
valence state within the metallic phase of BaV _{10}O_{15}
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,**

**Phys.
Rev. B 99, 035122 (2019).**

**Orbital-dependent
band renormalization in WTe _{2} 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,**

**Phys.
Rev. B 98, 205138 (2018).**

**Impact
of valence fluctuations on the electronic properties of RO_{1−x}F_{x}BiS_{2}**

**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,**

**Phys.
Rev. B 98, 144501 (2018).**

**Anomalous metallic state
with strong charge fluctuations in ****Ba _{x}Ti_{8}O_{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,**

**Phys.
Rev. 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, **

**Phys.
Rev. B 97, 121110(R) (2018).**

**Inhomogeneous electronic states associated with
charge-orbital order/disorder in BaV _{10}O_{15}
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, **

**Phys.
Rev. B 96, 115161 (2017).**

**Orbital order and fluctuations in the two-leg ladder
materials BaFe _{2}X_{3} **

**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, **

**Phys.
Rev. B 96, 115157 (2017).**

**Phys.
Rev. B 96, 125147 (2017).**

**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