## Topological insulators and superconductors

Recent researches showed the existence of entirely new quantum states called topological insulators and topological superconductors. They got a great deal of attention in condensed matter physics field. These materials have gap structure in the bulk, but on the surface there are gapless excitation modes representable using beautiful mathematics (topology). The surface states of three-dimensional topological insulator can be described as two-dimensional massless relativistic Dirac particles, while three-dimensional superconductors can be described as Majorana particles. Our theoretical group is working on theory of the thermal conductivity and electrical conductivity, especially effects of the disorder and interaction, of the surface of topological materials and their electromagnetic and thermal response and the application to spintronics.