OKAZAKI Kozo
(Associate Professor/Division of Transdisciplinary Sciences)
Department of Advanced Materials Science/ laser photoemission spectroscopy, superconductivity, strongly correlated electron system
Career Summary
1998: Graduated from Faculty of Science (University of Tokyo)
2003: Received science doctorate from University of Tokyo
2003: Institute Researcher (University of Tokyo)
2003: Assistant Professor (Nagoya University)
2010: Project Researcher (University of Tokyo)
2013: Assistant Professor (University of Tokyo)
2014: Project Associate Professor (University of Tokyo)
2019: Associate Professor (University of Tokyo)
Educational Activities
Graduate school:Complex Material Science, Advanced Material Science II
Research Activities
Angle-resolved photoemission spectroscopy is a very powerful experimental technique that can directly observe a dispersion relation between momentum and energy (band structure) of the electrons in solid-state materials, whereas by utilizing a femtosecond laser as pumping light and its high harmonic generation (HHG) as probing light, we can observe ultrafast transient properties of the band structure in a non-equilibrium state. In our group, we are developing and improving a time-resolved photoemission apparatus that utilizes high harmonic generation of an ultrashort-pulse laser in collaboration with laser development groups, and aiming for understanding the mechanisms of electron relaxation dynamics from photo-excited states and demonstration of photo-induced superconductivity by direct observations of transient electronic states using pump-probe type time-resolved photoemission spectroscopy (TRPES). In addition, we are aiming for understanding the mechanisms of unconventional superconductivity by direct observations of the electronic structures and superconducting-gap structures of unconventional superconductors with a laser-based angle-resolved photoemission apparatus with a world-record performance that achieves a maximum energy resolution of 70 ?EeV and lowest cooling temperature of 1 K.
Literature
1) P. Zhang, Z. Wang, X. Wu, K. Yaji, Y. Ishida, Y. Kohama, G. Dai, Y. Sun, C. Bareille, K. Kuroda, T. Kondo, K. Okazaki, K. Kindo, X. Wang, C.-Q Jin, J.-P Hu, R. Thomale, K. Sumida, S.-L Wu, K Miyamoto, T. Okuda, H. Ding, G.D. Gu, T. Tamegai, T. Kawakami, M. Sato, and S. Shin: Multiple topological states in iron-based superconductors, Nat. Phys. 15, 41-47 (2019).
2) K. Okazaki, Y. Ogawa, T. Suzuki, T. Yamamoto, T. Someya, S. Michimae, M. Watanabe, Y.-F Lu, M Nohara, H. Takagi, N. Katayama, H. Sawa, M. Fujisawa, T. Kanai, N. Ishii, J. Itatani, T. Mizokawa, S. Shin: Photo-induced semimetallic states realised in electron-hole coupled insulators, Nat. Commun. 9, 4322 (2018).
3) D. Flototto, Y. Ota, Y. Bai, C. Zhang, K. Okazaki, A. Tsuzuki, T. Hashimoto, J. N. Eckstein, S. Shin and T. -C. Chiang, Sci. Adv. 4, eaar7214 (2018).
4) P. Zhang, K. Yaji, T. Hashimoto, Y. Ota, T. Kondo, K. Okazaki, Z. Wang, J. Wen, G. D. Gu, H. Ding and S. Shin, Science 360, 182 (2018).
5) K. Okazaki, H. Suzuki, T. Suzuki, T. Yamamoto, T. Someya, Y. Ogawa, M. Okada, M. Fujisawa, T. Kanai, N. Ishi, J. Itatani, M. Nakajima, H. Eisaki, A. Fujimori and S. Shin: Antiphase Fermi-surface modulations accompanying displacement excitation in a parent compound of iron-based superconductors, Phys. Rev. B 97, 121107(R) (2018).
6) T. Hashimoto, Y. Ota, H. Q. Yamamoto, Y. Suzuki, T. Shimojima, S. Watanabe, C. Chen, S. Kasahara, Y. Matsuda, T. Shibauchi, K. Okazaki and S. Shin: Superconducting gap anisotropy sensitive to nematic domains in FeSe, Nat. Commun. 9, 282 (2018).
7) K. Okazaki, Y. Ota, Y. Kotani, W. Malaeb, Y. Ishida, T. Shimojima, T. Kiss, S. Watanabe, C.-T. Chen, K. Kihou, C. H. Lee, A. Iyo, H. Eisaki, T. Saito, H. Fukazawa, Y. Kohori, K. Hashimoto, T. Shibauchi, Y. Matsuda, H. Ikeda, H. Miyahara, R. Arita, A. Chainani, and S. Shin: Octet-line node structure of superconducting order parameter in KFe2As2, Science 337, 1314 (2012)
Other Activities
The Physical Sciety of Japan (JPS)
American Physical Society (APS)
The Japanese Society for Synchrotron Radiation Research (JSSRR)
Future Plan
We will investigate the mechanism of unconventional superconductivity, and realize control of physical properties of materials by light.
Messages to Students
If you get interested in the research in my group, please contact me.