Akihiro TANAKA

Senior Researcher, Computational Materials Science Unit, National Institute for Materials Science

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■ Description of Research [187KB]

RESEARCH

Much of my work has centered around Berry phase effects in condensed matters. In 2005, I showed that a new Berry phase action can enter into and alter the low-energy description of 2d quantum antiferromagnets, an observation that has in recent years found applications/generalizations to the study of competing orders in topological insulators and superconductors. The present research stems from my past involvement with such Berry phase actions and their associated topological field theories (TQFTs), i.e. field theories sensitive only to global topological characteristics of the system, and are otherwise insensitive to configuration specifics. While universal properties of topological insulators and superconductors are generally describable in terms of TQFTs, there is an abundance of TQFTs for which links to condensed matters are yet to be established. We anticipate that this is fertile ground for new topological quantum effects, and pursue this direction in detail. For instance, establishing a connection between condensed matter systems and certain gravitational TQFTs may lead to quantum effects involving thermal transport or defect mediated channels.

EDUCATION

1990

B. Sc. Dept. Applied Physics, University of Tokyo

1992

M. S. Dept. Applied Physics, University of Tokyo

1999

Ph.D. Dept. Applied Physics, University of Tokyo

PROFESSIONAL EXPERIENCE

1995

Junior Research Fellow, Japan Atomic Energy Research Institute

2000

Researcher, National Research Institute for Metals

2001

Researcher, National Institute for Materials Research

2003-Present

Senior Researcher, National Institute for Materials Research

SELECTION OF PUBLICATIONS

"Photoinduced Transition between Conventional and Topological Insulators in Two-Dimensional Electronic Systems",
J. Inoue and A. Tanaka,
Phys. Rev. Lett. 105, 017401 (2010).

"Geometric phases and the magnetization process in quantum antiferromagnets",
A. Tanaka, K. Totsuka and X. Hu,
Phys. Rev. B 79,064412 (2009).

"Effective field theory with a θ-vacua structure for two-dimensional spin systems",
A. Tanaka and X. Hu,
Phys. Rev. B 74,140407 (2006).

"Competition between hidden spin and charge orderings in stripe phase",
C. Yasuda, A. Tanaka and X. Hu,
Phys. Rev. B 71,140507 (2005).

"Macroscopic Quantum Tunneling in a d-Wave High-TC Bi₂Sr₂CaCu₂O_8+δ Superconductor",
K. Inomata, S. Sato, K. Nakajima, A. Tanaka, Y. Takano, H. Wang, M. Nagao, H. Hatano and S. Kawabata,
Phys. Rev. Lett. 95,107005 (2005).

"Many-Body Spin Berry Phases Emerging from the π-Flux State: Competition between Antiferromagnetism and the Valence-Bond-Solid State",
A. Tanaka and X. Hu,
Phys. Rev. Lett. 95,036402 (2005).

"Possible Spin Triplet Superconductivity in Na_X CoO₂yH₂O",
A. Tanaka and X. Hu,
Phys. Rev. Lett. 91, 257006 (2003).

"Quantal Phases, Disorder Effects, and Superconductivity in Spin-Peierls Systems",
A. Tanaka and X. Hu,
Phys. Rev. Lett. 88,127004 (2002).

"Collective dynamics of Jospehson vortices in intrinsic Josephson junctions: exploration of in-phase locked superradiant vortex flow states",
M. Machida, T. Koyama, A. Tanaka and M. Tachiki,
Physica C 330, 85 (2000).

"Berry Phase from Vortex Dynamics in BCS superconductors revisited",
A. Tanaka and M. Machida,
Physica C 313, 141 (1999).

"Nonabelian Chiral Anomaly and the Spin-Gap in One-Dimensional Interacting Electron Systems",
A. Tanaka and M. Machida,
J. Phys. Soc. Jpn. 67, 748 (1998).

"Numerical Study of the S=1 Antiferromagnetic Spin Chain with Bond-Alternation",
Y. Kato and A. Tanaka,
J. Phys. Soc. Jpn. 63, 1277 (1994).