Wu QuanSheng, Liu Jianpeng, Guan Yifei, Yazyev Oleg V
Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
National Centre for Computational Design and Discovery of Novel Materials MARVEL, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
Phys Rev Lett. 2021 Feb 5;126(5):056401. doi: 10.1103/PhysRevLett.126.056401.
We propose Landau levels as a probe for the topological character of electronic bands in two-dimensional moiré superlattices. We consider two configurations of twisted double bilayer graphene (TDBG) that have very similar band structures, but show different valley Chern numbers of the flat bands. These differences between the AB-AB and AB-BA configurations of TDBG clearly manifest as different Landau level sequences in the Hofstadter butterfly spectra calculated using the tight-binding model. The Landau level sequences are explained from the point of view of the distribution of orbital magnetization in momentum space that is governed by the rotational C_{2} and time-reversal T symmetries. Our results can be readily extended to other twisted graphene multilayers and h-BN/graphene heterostructures thus establishing the Hofstadter butterfly spectra as a powerful tool for detecting the nontrivial valley band topology.
我们提出将朗道能级作为探测二维莫尔超晶格中电子能带拓扑特性的探针。我们考虑了扭曲双双层石墨烯（TDBG）的两种构型，它们具有非常相似的能带结构，但在平带处显示出不同的谷陈数。TDBG的AB-AB和AB-BA构型之间的这些差异在使用紧束缚模型计算的霍夫施塔特蝴蝶谱中明显表现为不同的朗道能级序列。从由旋转C₂和时间反演T对称性支配的动量空间中轨道磁化分布的角度解释了朗道能级序列。我们的结果可以很容易地扩展到其他扭曲的石墨烯多层膜和h-BN/石墨烯异质结构，从而将霍夫施塔特蝴蝶谱确立为检测非平凡谷带拓扑的有力工具。
