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

报告题目：Topologically Electronic States and Their ‘Coupling Effect’ in Two Dimensional Materials

报告人:杨中芹  复旦大学

报告时间：12月26日下午15:00-16:00

报告地点：致远楼213

报告邀请人： 江华

报告摘要：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.

报告人简介：杨中芹，复旦大学物理学系教授，1994年于南京大学物理系获学士学位，2000年于复旦大学物理学系获博士学位。2000年复旦大学化学系博士后；2001年美国Virginia Tech物理系博士后。2003年被聘为复旦大学物理系副教授，博士生导师，2008年晋升为教授。研究工作包括拓扑电子态、自旋-轨道耦合体系输运性质及纳米体系电荷、自旋量子输运性质的理论研究。近期在两维材料的量子反常Hall效应、量子自旋Hall效应等的拓扑电子态的方面开展了系列研究，预言了多种体系可以具有这一有趣的拓扑效应，提出出现这一效应的新机制，多次受邀在国内外重要学术会议上作邀请报告。在Phys. Rev. Lett.、Nano Lett.、Phys. Rev. B等著名学术期刊共发表论文80余篇，完成多项国家、上海市科研项目，承担两项在研国家自然科学基金项目。指导15名博士生和4名硕士生毕业并获学位。