Koichi IZAWA
Associate Professor, Department of Physics, Tokyo Institute of Technology- Topics of Research：
- Study of the low-energy quasiparticle excitations in the spin-triplet superconductor UPt3
■ Laboratory Website
■ Description of Research
[1264KB]
RESEARCH
The main research interest of my group lies in the physics of novel quantum states in strongly correlated electron systems, including unconventional superconductivity. We have been interested especially in the low-energy quasiparticle excitations in unconventional superconductors which are characteristic of the symmetry of their gap function. The clarification of the gap symmetry is crucial for understanding the pairing mechanism because it is intimately related to the pairing interaction. We therefore have performed heat transport measurements on various exotic superconductors at low temperatures down to 30 mK in order to clarify the gap symmetry.
Recently, we have revealed that spontaneous twofold symmetry breaking occurs in the gap function of the spin-triplet superconductor UPt3 by means of angle-resolved thermal conductivity tensor under magnetic field. This result leads us to conclude that the pairing state of UPt3 belongs to an E1u representation in the f-wave category. We also revealed that the E1u f-wave state is compatible with most of the experimental results reported until now. Interestingly, it has been pointed out theoretically that UPt3 with the E1u state can be a promising candidate for a topological superconductor with Majorana zero modes.
In this project "Topological Quantum Phenomena in Condensed Matter with Broken Symmetries", we pursue the study of low-energy quasiparticle excitation in UPt3 to obtain clues to clarifying its mechanism as well as to understand the nature of the spin-triplet superconductivity with multiple superconducting phases. I will also try to reveal novel phenomena characteristic of the topological nature.
EDUCATION
- 1993
- B.Sc. in Physics, Hiroshima University
- 1995
- M.S. in Physics, Hiroshima University
- 1998
- Ph.D. in Physics, Hiroshima University (Supervisor: Toshizo Fujita)
PROFESSIONAL EXPERIENCE
- 1998-2005
- Research Associate, Institute of Solid State Physics
- 2005-2006
- Marie-Curie Fellow, CEA-Grenoble, France (Host: Jacques Flouquet)
- 2006-Present
- Associate Professor, Department of Physics, Tokyo Institute of Technology
HONORS AND AWARDS
- 2004
- ISSP Young Scientist Medal
- 2007
- Young Scientist Award of the Physical Society of Japan
- 2009
- The Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology (The Young Scientists' Prize)
SELECTION OF PUBLICATIONS
"Twofold Spontaneous Symmetry Breaking in the Heavy-Fermion Superconductor UPt3",
Y. Machida , A. Itoh, Y. So, K. Izawa, Y. Haga, E. Yamamoto, N. Kimura, Y. Onuki, Y. Tsutsumi, and K. Machida
Phys. Rev. Lett. 108, 157002/1-5 (2012).
"Enhanced Quasiparticle Heat Conduction in the Multigap Superconductor Lu2Fe3Si5",
Y. Machida , S. Sakai, K. Izawa, H. Okuyama, and T. Watanabe
Phys. Rev. Lett. 106, 107002/1-4 (2011).
"Thermoelectric Response Near a Quantum Critical Point: The Case of CeCoIn5",
K. Izawa, K. Behnia, Y. Matsuda, H. Shishido, R. Settai, Y. Onuki, and J. Flouquet
Phys. Rev. Lett. 99, 147005/1-4 (2007).
"Nodal structure of unconventional superconductors probed by angle resolved thermal transport measurements",
Y.Matsuda, K. Izawa, I. Vekhter
J. Phys.: Condens. Matter 18, R705-752 (2006).
"Line nodes in the superconducting gap function of noncentrosymmetric CePt3Si",
K. Izawa, Y. Kasahara, Y. Matsuda, K. Behnia, T. Yasuda, R. Settai, Y. Onuki
Phys. Rev. Lett. 94, 197002/1-4 (2005).
"Multiple superconducting phases in new heavy fermion superconductor PrOs4Sb12",
K. Izawa, Y. Nakajima, J. Goryo, Y. Matsuda, S. Osaki, H. Sugawara, H. Sato, P. Thalmeier, and K. Maki
Phys. Rev. Lett. 90, 117001/1-4 (2003).
"Gap Function with Point Nodes in Borocarbide Superconductor YNi2B2C",
K. Izawa, K. Kamata, Y. Nakajima, Y. Matsuda, T. Watanabe, M. Nohara, H. Takagi, P. Thalmeier and K. Maki
Phys. Rev. Lett. 89, 137006/1-4 (2002).
"Angular Position of Nodes in the Superconducting Gap of Quasi-2D Heavy-Fermion Superconductor CeCoIn5",
K. Izawa, H. Yamaguchi, Y. Matsuda, H. Shishido, R. Settai, and Y. Onuki
Phys. Rev. Lett. 87, 057002/1-4 (2001).
