Ma Zhen, Li Shuai, Zheng Ya-Wen, Xiao Meng-Meng, Jiang Hua, Gao Jin-Hua, Xie X C
School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China.
School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
Sci Bull (Beijing). 2021 Jan 15;66(1):18-22. doi: 10.1016/j.scib.2020.10.004. Epub 2020 Oct 16.
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.
扭曲三层石墨烯（TLG）可能是目前为止最简单的具有非平凡拓扑结构平带的实际体系。在此，我们利用连续模型对其能带结构以及能带拓扑，即近平带的谷陈数进行了全面计算。采用实际参数时，扭曲TLG的魔角约为1.12°，此时会出现两条近平带。与扭曲双层石墨烯不同，小的扭曲角会在所有狄拉克点处诱导出微小能隙，该能隙可通过垂直电场进一步增大。扭曲TLG中两条近平带的谷陈数取决于扭曲角θ和垂直电场E。考虑到其拓扑平带，扭曲TLG应该是研究拓扑非平凡平带体系中强关联物理的理想实验平台。而且，由于其对称性降低，扭曲TLG中的关联态应该与扭曲双层石墨烯和扭曲双双层石墨烯中的关联态有很大不同。
