论文标题
Moiré石墨烯中Chern绝缘子山谷中没有边状态
Absence of Edge States in The Valley Chern Insulator in Moiré Graphene
论文作者
论文摘要
我们研究了在连续模型预测谷化Chern绝缘子的情况下，单层和双层石墨烯的扭曲板的边缘光谱 - 在每个山谷中，每个山谷中占领的Moiré迷你频段都有一个净CHERN号码，但是两个谷地都没有净chern nubl Chern编号，因为时间逆转的净值对称是对称的。在简单的图片中，可能有望具有手性山谷两极化的反向通向边缘状态。我们提出了带状几何形状中相当结构的紧密结合模型的对角度的结果。我们发现，对于单层和双层MoiréRibbons而言，强大的边缘模式通常不存在。我们将这种缺乏边缘模式归因于边缘引起山谷混合的事实。此外，即使在散装中，山谷奇恩绝缘子和微不足道的绝缘子之间也需要一个精确的$ C_3 $对称性。
We study the edge spectrum of twisted sheets of single layer and bilayer graphene in cases where the continuum model predicts a valley Chern insulator -- an insulating state in which the occupied moiré mini-bands from each valley have a net Chern number, but both valleys together have no net Chern number, as required by time reversal symmetry. In a simple picture, such a state might be expected to have chiral valley polarized counter-propagating edge states. We present results from exact diagonalization of the tight-binding model of commensurate structures in the ribbon geometry. We find that for both the single-layer and bilayer moiré ribbons robust edge modes are generically absent. We attribute this lack of edge modes to the fact that the edge induces valley mixing. Further, even in the bulk, a sharp distinction between the valley Chern insulator and a trivial insulator requires an exact $C_3$ symmetry.
