Exotic interaction-driven Topological Phases and Topological Phase Transitions

报告题目：Exotic interaction-driven Topological Phases and Topological Phase Transitions

报告时间：11月25日（本周五）16：00

报告地点：基础学科大楼二楼大会议室B253

报 告人：何院耀，中国人民大学物理系&&中科院物理所 博士研究生

报告摘要：

Topology in condensed matter physics has been widely studied in the past several decades, and it’s also awarded the Nobel Prize in 2016. Although the topological phases in free fermion systems, such as 3D topological insulators, are elegantly classified and almost fully understood, the correlation effects on topological insulators remains a challenge. In our work, we apply the large scale Quantum Monte Carlo (QMC) simulations to study various interacting fermionic models containing nontrivial topology and electron-electron interactions. Especially, we have identified a continuous interaction-driven topological phase transition in bilayer Kane-Mele-Hubbard model, which has no free-fermion and mean-field correspondence, rendering a fully new quantum critical point. Furthermore, this topological phase transition has an exact mapping to Nonlinear Sigma Model plus topological Theta term in quantum field theory. So this is actually the very first time that we can simulate a Quantum Field Theory by QMC without sign problem. And by combining Exact Diagonalization method and symmetry analysis, we have identified an interaction-driven Chern insulator, in a square lattice model of spinless fermions with quadratic band touching, by tuning interaction strength. This is also the first time that such an interaction-driven topological phase is verified by an unbiased numerical method.