Topological flat bands in twisted trilayer graphene

Zhen Ma; Shuai Li; Ya-Wen Zheng; Meng-Meng Xiao; Hua Jiang; Jin-Hua Gao; X C Xie

doi:10.1016/j.scib.2020.10.004

Topological flat bands in twisted trilayer graphene

Sci Bull (Beijing). 2021 Jan 15;66(1):18-22. doi: 10.1016/j.scib.2020.10.004. Epub 2020 Oct 16.

Authors

Zhen Ma¹, Shuai Li¹, Ya-Wen Zheng¹, Meng-Meng Xiao¹, Hua Jiang², Jin-Hua Gao³, X C Xie⁴

Affiliations

¹ School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China.
² School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
³ School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China. Electronic address: jinhua@hust.edu.cn.
⁴ International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China; Collaborative Innovation Center of Quantum Matter, Beijing 100871, China; CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China.

PMID: 36654307
DOI: 10.1016/j.scib.2020.10.004

Abstract

Twisted trilayer graphene (TLG) may be the simplest realistic system so far, which has flat bands with nontrivial topology. Here, we give a comprehensive calculation about its band structures and the band topology, i.e., valley Chern number of the nearly flat bands, with the continuum model. With realistic parameters, the magic angle of twisted TLG is about 1.12°, at which two nearly flat bands appears. Unlike the twisted bilayer graphene, a small twist angle can induce a tiny gap at all the Dirac points, which can be enlarged further by a perpendicular electric field. The valley Chern numbers of the two nearly flat bands in the twisted TLG depends on the twist angle θ and the perpendicular electric field E_⊥. Considering its topological flat bands, the twisted TLG should be an ideal experimental platform to study the strongly correlated physics in topologically nontrivial flat band systems. And, due to its reduced symmetry, the correlated states in twisted TLG should be quite different from that in twisted bilayer graphene and twisted double bilayer graphene.

Keywords: Moiré heterostructure; Topological flat bands; Twisted trilayer graphene; Valley Chern number.