Prof. Yoichi Ando (Institute of Scientific and Industrial Research, Osaka University)
"Topological Insulators and Superconductors"
A topological state of matter is characterized by a topological feature of the quantum-mechanical wavefunction in the Hilbert space. In topological insulators, a non-trivial Z2 topology of the bulk valence band leads to the emergence of helical Dirac fermions on the surface. Similarly, in topological superconductors, non-trivial Z or Z2 topologies of the superconducting wavefunctions lead to the appearance of Majorana fermions on the surface. The Dirac or Majorana fermions in those topological states of matter are not only of intellectual interest, but they are also expected to play a key role in future information devices; therefore, there is a surge of research on topological insulators and superconductors in the past few years. Thanks to the recent discoveries of various topological insulators, it has become possible to experimentally address the transport properties of the helical Dirac fermions, but a concrete example a topological superconductor is still to be discovered and Majorana fermions remain elusive. In this talk, after an ample introduction, I will introduce some of the most exciting results from our materials-oriented research of those materials at Osaka.