The last decade has witnessed a remarkable expansion in the understanding of topological states of matter. A quantum state is topological if its ground state wave function bears a distinctive character that can be specified by a topological invariant. While known in both theory and experiment since the 1980s, the recent revolution in topology has been fueled by combination of topology and symmetry, which gives rise to novel states such as topological insulator and topological crystalline insulator. In this talk, I will discuss material realizations and their corresponding novel properties of these symmetry-related topological states and focus on two examples: monolayer WTe2 class of quantum spin Hall insulators and PbxSn1- x(Se,Te) class of topological crystalline insulators. Both of these predictions have both been confirmed by several independent experimental groups. The theoretical studies also impulse our discovery of the thinnest ferroelectric materials in SnTe thin films with the experimental group. At last, I will briefly show our newly designed general-purpose numerical method, dubbed self-learning Monte Carlo, which can be 103 faster than traditional Monte Carlo method and is very powerful to study the topological states and other interesting properties in strongly correlated systems of large size.
About the Speaker
Dr Junwei Liu received the BS from Xian Jiaotong University, China and then went to Tsinghua University in Beijing China for his PhD study under the supervision of Prof Binglin Gu and Prof Wenhui Duan. He has been working with Prof Liang Fu at MIT as a postdoctoral researcher since his graduation from Tsinghua University.