学术沙龙（4月25日 16:00 – 17:30）

主持人：项泽亮 教授

欢迎广大师生前来参与！

【摘要】

Topological phases of quantum matter have been widely studied in closed systems, which are described by Hermitian Hamiltonians with real eigenvalues and a set of orthogonal eigenfunctions. Recently, there has been a great deal of interest in studying topological phases of open systems governed by non-Hermitian operators, altering the nature of the usual bulk-boundary correspondence in topological systems. Meanwhile, in the context of Hermitian topological systems, the concept of topological insulators has been generalized to higher-order topological insulators. In contrast to conventional first-order topological phases, a d-dimensional second-order topological insulator (SOTI) can host topologically protected (d¬-2)-dimensional gapless boundary modes. In this talk, I will start with an overview of non-Hermitian phenomena and higher-order topological phases. Then I will present our investigation of non-Hermitian seconder-order topological insulators.
封闭量子系统可以被具有实本征能量和正交本征矢的厄密哈密顿量来描述，而这类系统中的拓扑量子相位也已经被广泛地研究。最近，作为拓扑系统中正常体态与边界相关性研究的延伸，对于由厄密算符主导开放系统的拓扑相位引起了很大的关注。同时，厄密拓扑系统中拓扑绝缘体的概念也被延伸到了高阶。对比于通常的一阶拓扑相位，d维二阶拓扑绝缘体可以拥有拓扑保护的（d-2）维带隙边缘模式。在这次讲座中，我将先介绍费厄密现象和高阶拓扑相位，在介绍我们对于非厄密二阶拓扑绝缘体的研究。

【报告人简介】

Tao Liu received his Ph.D. in Nanyang Technological University in the year of 2014, Singapore. He spent three years in the same university as a postdoctoral researcher, and is currently working as JSPS Post-doctoral Fellowship in Theoretical Quantum Physics Laboratory, Riken, Japan. His research interests are mainly focusing on topological quantum phases of matter, non-Hermitian physics and the applications of quantum information concepts to quantum many-body systems. Until now, he has published 26 papers, including Physical Review Letter, Nature Communications, and Physical Review B,  with total citation larger than 820