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arXiv 2007.15489cond-mat.mes-hall
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扭曲多层石墨烯中的谷选择性Floquet Chern平坦带

Valley-selective Floquet Chern Flat Bands in Twisted Multilayer Graphene

Ming Lu, Jiang Zeng, Haiwen Liu, Jin-Hua Gao, X. C. Xie

摘要:

我们发现,Floquet工程与圆偏振光(CPL)可以选择性地分裂扭曲多层石墨烯(TMG)的谷简并,从而产生一个可控的谷偏振Floquet陈平带可调大陈数。这为控制莫尔平带的谷自由度提供了一种可行的光学方法,从而为研究莫尔平带系统的谷电子学提供了新的机会。因此,我们期望TMG的许多谷相关性质,例如轨道铁磁性,可以通过适当掺杂的CPL来切换。我们揭示了一个通用的(M+N)层TMG的Floquet平坦带的陈数层次规则。我们还说明了CPL对TMG的影响强烈依赖于堆叠手性,这是TMG的一个独特功能。所有这些现象都可以在扭曲双层石墨烯系统中得到验证,这是TMG的最简单的例子,并且已经在实验中实现。

英文摘要:

We show that Floquet engineering with circularly polarized light (CPL) can selectively split the valley degeneracy of a twisted multilayer graphene (TMG), and thus generate a controlled valley-polarized Floquet Chern flat band with tunable large Chern number. It offers a feasible optical way to manipulate the valley degree of freedom in moiré flat bands, and hence opens new opportunities to study the valleytronics of morié flat band systems. We thus expect that many of the valley-related properties of TMG, e.g. orbital ferromagnetism, can be switched by CPL with proper doping. We reveal a Chern number hierarchy rule for the Floquet flat bands in a generic (M+N)-layer TMG. We also illustrate that the CPL effects on TMG strongly rely on the stacking chirality, which is an unique feature of TMG. All these phenomena could be tested in the twisted double bilayer graphene systems, which is the simplest example of TMG and has already been realized in experiment.

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