# Colloquium20150428-Topological crystalline insulators: A new type of topological materials

Colloquium

Department of Physics, NCU

Topological crystalline insulators: A new type of topological materials

Speaker

Dr. Wei-Feng Tsai (蔡維楓)

Assistant Professor

Department of Physics, National Sun Yat-sen University

Date 2015.4.28(Tue)

Time 14:00

Place S4-625

「歡迎大學部同學參加，可獲得中大護照認證2小時」

Abstract:

Topological insulators belong to a new phase of matter with their topological nature protected by time reversal symmetry. Since their discovery condensed matter physicists have made enormous effort in the manipulation and possible application of them as well as a hunt for new materials with non-trivial topology, including topological superconductors. However, recently discovered topological crystalline insulators, Pb$_{\mathrm{1-x}}$Sn$_{\mathrm{x}}$(Te, Se), can harbor multiple Dirac surface states, which are protected by a discrete set of crystalline symmetries rather than time reversal symmetry. In this talk, I will compare the physical properties of these materials with those in topological insulators.

In particular, the new possibilities opened by the presence of the multiple Dirac surface states will be discussed through concrete examples.