We theoretically study electric states in solids, magnetism, superconductivity, quantum transport, and so on. The main topic in our group is the theories of strongly correlated electron systems such as transition metal, actinides and rare-earth compounds. In these materials, varieties of exotic physical properties emerge at low temperatures due to the strong interactions between the electric charge, spin, orbital and lattice distortions, etc. Our ultimate aim is to find the universal principle which explains seemingly different exotic phenomena in a unified manner.

#### Research

In our group, we have studied strongly correlated electron systems (SCES) such as transition metal, actinide and rare earth compounds, in which large Coulomb repulsion plays important role, using both analytic and numerical methods. In SCES, there appear variety of phases in low temperature, for example, magnetism, superconductivity, and charge density wave, etc. The purpose of our group is to obtain a unified picture of these complex systems and to find new physics in such systems.
Our recent subjects are complex orderings due to couplings between electron's spin and orbital degrees of freedom and new quantum mechanical orders in frustrated spin systems. The essential point in frustrated system is that there are a lot of low energy modes and these fluctuations. These consist of, for example, different oscillation modes in space and different fluctuations in the inner degrees of freedom (such as charge, spin, orbital etc.). We are interested in the nature of the order, its critical phenomena, the electron states, and the transport in these systems.

Our current subjects:

- Electron states in SCES
- Theory of quantum magnets
- Theory of transition, actinide and rare earth compounds
- Statistical physics in frustrated systems
- Heavy fermion systems
- Topological Superconductors
- Floquet-theoretical study of nonlinear and nonequilibrium phenomena
- Transport phenomena in exactly solvable models

#### Seminar

Reading club is held every week
to learn fundamentals of condensed matter theory.

In 2019, the following text book is used.

- "Statistical Field Theory: An Introduction to Exactly Solved Models in Statistica\
l Physics" (G. Mussardo)