题目：转角石墨烯系统中的拓扑电子和关联电子态：Topological and correlated states in twisted graphene systems

报告人: 刘健鹏  教授

时间：4月15日（周四），下午14:00 

地点：师昌绪楼408 

摘要 

We discuss the topological properties and correlated states in twisted bilayer graphene (TBG) and twisted multilayer graphene systems. We first show that the leading-order effect of the moire potential in TBG is to generate opposite pseudo magnetic fields coupled with two flavors of Dirac fermions, which gives rise to pseudo Landau levels, and the flat bands in magic-angle TBG arederived from the two zeroth pseudo Landau levels. The experimentally observed quantum anomalous Hall effects and the origin of the magic angles can be naturally explained using such a pseudo-Landau-level picture. We also show that the topologically nontrivial flat bands also generically exist in twisted multilayer graphene systems with tunable valley Chern numbers. We further study the nature of the correlated insulator states observed in TBG, and predict that the ground states at even integer fillings in TBG are valley polarized states associated with intriguing compensating current-loop patterns in real space. In the end we discuss the experimentally observed correlated insulator states in twisted multilayer graphene systems. 

[1] JianpengLiu, Junwei Liu, Xi Dai, Phys. Rev. B, 99 (15), 155415 (2019) 

[2] Jianpeng Liu, Zhen Ma, Jinhua Gao, Xi Dai, Phys. Rev. X, 9 (3), 031021 (2019) 

[3] JianpengLiu, Xi Dai, Phys. Rev. B, 103 (3), 035427 (2021) 

[4] Shihao Zhang, Jianpeng Liu, arXiv:2101.04711v2 

个人简介 

　　刘健鹏教授于2010年本科毕业于南开大学物理学院，后师从David Vanderbilt教授，2015年于美国罗格斯大学博士毕业，随后前往UCSB Leon Balents研究组以及香港科大戴希研究组先后担任博士后以及研究助理教授等职位。从2020年5月至今，刘健鹏在上海科技大学任博导、研究员以及终身制序列助理教授。刘健鹏的研究方向为理论和计算凝聚态物理学，具体包括：拓扑材料与物态、磁性材料、转角二维体系以及摩尔二维体系的关联性质、输运性质以及电子结构理论，量子材料的输运性质以及非线性光学性质的理论研究，以及基于密度泛函理论的计算方法研究等等。