旋转双层石墨烯的电子结构

Electronic structure of twisted bilayer graphene

本文将第一性原理和紧束缚方法结合起来,研究了层间不同旋转角度对双层石墨烯的电子能带结构和态密度的影响.分析发现,旋转双层石墨烯具有线性的电子能量色散关系,但其费米速度随着旋转角度的减小而降低.进一步研究其电子能带结构发现,不同旋转角度的双层石墨烯在M点可能会出现大小不同的的带隙,而这些能隙会增强双层石墨烯的拉曼模强度,并由拉曼光谱实验所证实.通过对比双层石墨烯的晶体结构和电子态密度,发现M点处带隙来自于晶体结构中的"类AB堆垛区".

This paper uses the first-principles and the tight-binding methods to study the electronic structures of twisted bilayer graphene for different angles. The band structures and density of states of twisted bilayer graphene in different angles are calculated. Our analysis points out that there is a linear dispersion relation in a twisted bilayer graphene, which is similar to a monolayer graphene, and the Fermi velocity of twisted graphene is lower and lower with reducing angle. Furthermore, gaps appearing at M point of certain angles, in which the width of gap depends on the twist angle, this gap would strengthen the Raman mode intensity of twisted bilayer graphene, as was confirmed by experiment. The comparison of moire’ patterns and the location of density of states both certify that ‘AB region’ of moire’ patterns is the reason of gap at M point.