北京大学物理学院

报告摘要：

Two-dimensional (2D) Stiefel-Whitney insulator (SWI), which is characterized by the second Stiefel-Whitney class, is a class of topological phases with zero Berry curvature. As an intriguing topological state, it has been well studied in theory but seldom realized in realistic materials. Here we propose that a large class of liganded Xenes, i.e., hydrogenated and halogenated 2D group-IV honeycomb lattices, are 2D SWIs. The nontrivial topology of liganded Xenes is identified by the bulk topological invariant and the existence of protected corner states. Moreover, the large and tunable band gap (up to 3.5 eV) of liganded Xenes will facilitate the experimental characterization of the 2D SWI phase. Our findings not only provide abundant realistic material candidates that are experimentally feasible, but also draw more fundamental research interest towards the topological physics associated with Stiefel-Whitney class in the absence of Berry curvature.

报告人简介：

Huaqing Huang received his B.S. in mathematics and physics, and Ph.D. in condensed matter physics from Tsinghua University in 2011 and 2016, respectively. After that, he worked at the University of Utah as a postdoctoral from 2016-2019. He joined school of physics, Peking University in 2020. Dr. Huang’s current research interests include topological states and phase transitions in periodic and nonperiodic systems (e.g., quasicrystals, and amorphous systems); first-principles investigation of new materials with exotic physical phenomena, and the development of method for electronic structure calculations. Dr. Huang has published over 56 articles in scientific journals (e.g. PRL, Nano Lett. and Nature Commun.) with more than 3000 citations and has a Web of Science h-index of 26.

邀请人：刘  淼  副研究员（9407）

联系人：张  萃  副研究员（8609）