Quantum Matter Theory Research Team

Principal Investigator

PI Name Akira Furusaki
Degree D.Sci.
Title Team Leader
Brief Resume
1991 Research Associate, Department of Applied Physics, University of Tokyo
1993 Ph.D., University of Tokyo
1993 Postdoctoral Associate, Massachusetts Institute of Technology, USA
1995 Research Associate, Department of Applied Physics, University of Tokyo
1996 Associate Professor, Yukawa Institute for Theoretical Physics, Kyoto University
2003 Chief Scientist, Condensed Matter Theory Laboratory, RIKEN (-present)
2013 Team Leader, Quantum Matter Theory Research Team, Strong Correlation Physics Division, RIKEN Center for Emergent Matter Science (-present)


We investigate novel quantum phases of many-electron systems in solids which emerge as a result of strong electron correlation and quantum effects. We theoretically study electronic properties of these new phases (such as transport and magnetism) and critical phenomena at phase transitions. Specifically, we study topological insulators and superconductors, frustrated quantum magnets, and other strongly correlated electron systems in transition metal oxides and molecular conductors, etc. We construct effective models for electrons in these materials and unveil their various emergent phases by solving quantum statistical mechanics of these models using both analytical and numerical methods.

Research Fields

Physics, Materials Science


Electron correlation
Frustrated quantum magnets
Topological insulators


Classifying topological insulators and topological superconductors

Modern electronics is based on the band theory that describes quantum mechanical motion of electrons in a solid. The band theory can explain properties of metals, insulators and semiconductors, and led to the invention of transistors. However, recent studies revealed some important physics which was missed in the standard band theory. Namely, the geometric (Berry) phase of electron wave functions can have a nontrivial topological structure in momentum space, and this leads to a topological insulator. In addition, superconductors with gapped quasiparticle excitations can be a topological superconductor. In principle there are various types of topological insulators (TIs) and topological superconductors (TSCs) in nature.

We constructed a general theory that can classify TIs and TSCs in terms of generic symmetries.  This theory shows that in every spatial dimension there are three types of TIs/TSCs with an integer topological index and two types of TIs/TSCs with a binary topological index. We extend our theory to understand the effect of crystalline symmetry and electron correlation.



A coffee mug and a donut are equivalent in topology because they can be continuously deformed from one to the other. The wave functions of electrons in insulators can be topologically lassified.


Akira Furusaki

Team Leader furusaki[at]riken.jp

Tsutomu Momoi

Senior Research Scientist

Shigeki Onoda

Senior Research Scientist

Hitoshi Seo

Senior Research Scientist

Shingo Kobayashi

Research Scientist

Ikuma Tateishi

Postdoctoral Researcher


  1. Y. Yao, M. Oshikawa, and A. Furusaki

    Gappability Index for Quantum Many-Body Systems

    Phys. Rev. Lett. 129, 017204 (2022)
  2. S. Kobayashi, and A. Furusaki

    Fragile topological insulators protected by rotation symmetry without spin-orbit coupling

    Phys. Rev. B 104, 195114 (2021)
  3. S. Furukawa, and T. Momoi

    Effects of Dzyaloshinskii-Moriya Interactions in Volborthite: Magnetic Orders and Thermal Hall Effect

    J. Phys. Soc. Jpn. 89, 034711 (2020)
  4. M. Naka, S. Hayami, H. Kusunose, Y. Yanagi, Y. Motome, and H. Seo

    Spin current generation in organic antiferromagnets

    Nat. Commun. 10, 4305 (2019)
  5. S. Onoda, and F. Ishii

    First-Principles Design of the Spinel Iridate Ir2O4 for High-Temperature Quantum Spin Ice

    Phys. Rev. Lett. 122, 067201 (2019)



3F Main Research Building, 2-1 Hirosawa, Wako, Saitama 351-0198 Japan