Educational Activities

Graduate School of Frontier Sciences: Optical Properties of Solids (1999~2003), Optical Properties of Solids A (2004~)
Faculty of Engineering: Introduction to Optical Properties of Solids (1999~2003), Optics (2004~)
Adjunct Professor: Tokyo Institute of Technology (2000), Graduate School of Art and Sciences,
University of Tokyo (2003), Nagoya University (2004), Osaka University (2004)

Research Activities

Research contents
Low dimensional materials show interesting physical properties originating from their unique crystal and electronic structures, which are not observed in conventional three-dimensional (3D) semiconductors. In our laboratory, we are exploring novel optical phenomena and new photonic functions in low dimensional materials, and studying their mechanisms by means of various kinds of nonlinear spectroscopy and ultrafast laser spectroscopy, including:
(1) exploration of gigantic optical nonlinearity in low-dimensional strongly correlated electron systems (SCESs), conjugated polymers, and single-walled carbon nanotubes (SWNTs);
(2) study of ultrafast optical responses in SCESs, conjugated polymers, and SWNTs;
(3) study of photoinduced insulator-metal transition in transition metal compounds and organic charge-transfer complexes; and (4) exploration of photoinduced magnetic and ferroelectric phase transitions.

Research activities
Discovery of gigantic dielectric responses in organic charge-transfer complexes (ref. 2)
Clarification and tuning of electronic structures in one-dimensional transition-metal complexes (refs. 1, 4, 6)
Clarification of dynamical aspects of solitons, polarons, and excitons in one-dimensional transition-metal complexes (refs. 3, 5, 6)
Discovery of gigantic nonlinear optical responses in one-dimensional strongly correlated electron systems (refs. 7, 8, 13)
Clarification of ultrafast dynamics of photoinduced neutral-ionic transition and its coherent control in organic charge-transfer complexes (refs. 9, 14, 21)
Discovery of photoinduced magnetic phase transitions in one-dimensional correlated electron systems (refs. 10, 11, 18)
Discovery of ultrafast photoinduced insulator-metal transition in one-dimensional correlated electron systems (refs. 12, 17, 22)
Clarification of the mechanism of photoinduced melting of ferromagnetic magnetization (ref. 16)
Discovery of coherent nonlinear optical responses in carbon nanotubes (refs. 15, 20)
Realization of coherent control of photoinduced transition dynamics (ref. 19)
Discovery of photoinduced insulator-ferromagnetic metal transition in strongly correlated electron systems (ref. 23)

Literature

1) H. Okamoto, K. Toriumi, T. Mitani, and M. Yamashita, Physical Review B, 42, 10381-10387 (1990).
2) H. Okamoto et al., Physical Review B, 43, 8224-8232 (1991).
3) H. Okamoto, T. Mitani, K. Toriumi, and M. Yamashita, Physical Review Letters, 69, 2248-2251 (1992).
4) H. Okamoto et al., Physical Review B, 54, 8438-8445 (1996).
5) H. Okamoto et al., Physical Review Letters, 80, 861-864 (1998).
6) H. Okamoto and M. Yamashita, Bulletin of the Chemical Society of Japan, Accounts, 71, 2023-2039 (1998).
7) H. Kishida, H. Matsuzaki, H. Okamoto, T. Manabe, M. Yamashita, Y. Taguchi, and Y. Tokura, Nature, 405, 929-932 (2000).
8) H. Kishida, M. Ono, K. Miura, H. Okamoto, M. Izumi, T. Manako, M. Kawasaki, Y. Taguchi, Y. Tokura, T. Tohyama, K. Tsutsui, and S. Maekawa, Physical Review Letters, 87, 177401-177404 (2001).
9) S. Iwai, S. Tanaka, K. Fujinuma, H. Kishida, H. Okamoto, and Y. Tokura, Physical Review Letters, 88, 57402-57405 (2002).
10) H. Matsuzaki, T. Matsuoka, H. Kishida, K. Takizawa, H. Miyasaka, K. Sugiura, M. Yamashita, and H. Okamoto, Physical Review Letters, 90, 46401-46404 (2003).
11) H. Matsuzaki, W. Fujita, K. Awaga, and H. Okamoto, Physical Review Letters, 91, 17403 (2003).
12) S. Iwai, M. Ono, H. Matsuzaki, H. Kishida, H. Okamoto, and Y. Tokura, Physical Review Letters, 91, 57401-57404 (2003).
13) M. Ono, K. Miura, A. Maeda, H. Matsuzaki, H. Kishida, Y. Taguchi, Y. Tokura, M. Yamashita, and H. Okamoto, Physical Review B, 70, 85101-85120 (2004).
14) H. Okamoto et al., Physical Review B, 70, 165202-165219 (2004).
15) A. Maeda, S. Matsumoto, H. Kishida, T. Takenobu, Y. Iwasa, M. Shiraishi, M. Ata, and H. Okamoto, Physical Review Letters, 94, 47404-47407 (2005).
16) T. Ogasawara, K. Ohgushi, Y. Tomioka, K. S. Takahashi, H. Okamoto, M. Kawasaki, and Y. Tokura, Physical Review Letters, 94, 87202-87205 (2005).
17) S. Iwai and H. Okamoto, Journal of the Physical Society of Japan, 75, 11007-11027 (2006).
18) H. Okamoto et al., Physical Review Letters, 96, 37405-37408 (2006).
19) S. Iwai, Y. Ishige, S. Tanaka, Y. Okimoto, Y. Tokura, and H. Okamoto, Physical Review Letters, 96, 57403-57406 (2006).
20) A. Maeda, S. Matsumoto, H. Kishida, T. Takenobu, Y. Iwasa, H. Shimoda, O. Zhou, M. Shiraishi, and H. Okamoto, Journal of the Physical Society of Japan, 75, 43709-437012 (2006)
21) H. Okamoto et al., Physical Review Letters, 98, 37401-37404 (2007).
22) S. Iwai, K. Yamamoto, A. Kashiwazaki, F. Hiramatsu, H. Nakaya, K. Yakushi, H. Okamoto, H. Mori, and Y. Nishio, Physical Review Letters, 98, 97401-97404 (2007).
23) M. Matsubara, H. Okamoto et al., Physical Review Letters, in press.

Other Activities

Member of the Physical Society of Japan
Member of the Chemical Society of Japan
Member of the Fullerenes and Nanotubes Research Society
Researcher at PRESTO, Japan Science and Technology Agency (1998~2001)
Leader of Photonics Team in Correlated Electron Research Center, National Institute of Advanced Science and Technology (2001~)
Member of editorial board in the Physical Society of Japan (2006~)

Future Plan

I aim to explore and develop new optical functionalities, especially gigantic optical nonlinearity and ultrafast optical switching, in correlated electron systems.

Messages to Students

I hope that you will develop original findings and discoveries in your graduate research.

URL

http://pete.k.u-tokyo.ac.jp/e_index.html