Topologically Electronic States and Their ‘Coupling Effect’ in Two Dimensional Materials

Title: Topologically Electronic States and Their ‘Coupling Effect’ in Two Dimensional Materials

Speaker: Yang Zhongqin

Location: Room 213, Zhiyuan Building

Time: 15:00-16:00p.m. Dec 26th, 2018

Abstract: The topological states, including quantum spin Hall (QSH), quantum anomalous Hall (QAH), and their hybrid states, are investigated in two-dimensional (2D) triangular lattices with multiorbitals. The band structure of a simple 2D triangular lattice in the basis of (px, py) contains band degeneracy not only at the Γ point but also at the K/K’ points. Based on the tight-binding (TB) model, the global SOC-induced band gap is found to be topologically trivial due to the destructive ‘coupling effect’ of the topological states at the Γ and K/K’ points. QSH and QAH states can be achieved in the bi-triangular lattice due to the breakdown of the destructive ‘coupling effect’. Metal-organic framework of TPyB-Co is an intrinsic Chern insulator, rationalized well by the bi-triangular TB model. Low-buckled plumbene is a trivial insulator due to constructive ‘coupling effect’ of the topological states. Strong SOC can induce topological phase transition, from nontrivial states to trivial states. Our findings are helpful to understand the topological states and provide new thoughts to search for new QSH and QAH materials.