论文标题
在非魔法角扭曲双层石墨烯中Chern绝缘状态的出现
Emergence of Chern insulating states in non-Magic angle twisted bilayer graphene
论文作者
论文摘要
发现将两层扭曲成〜1.1°的魔法角度（MA），这对于创建低能扁平带，以及所得的相关绝缘，超导和磁性阶段在扭曲的双层石墨烯（TBG）中必不可少。尽管以前的大多数作品都集中在MA-TBG中揭示这些新兴状态，但对扭曲角度依赖性的研究有助于绘制这些阶段的演变，但仍未得到探索。在这里，我们在一个非魔法角度TBG设备上报告了一项磁通量研究，其扭曲角θ从一端的1.25°变为另一端的1.43°。对于θ= 1.25°，我们观察到孔子侧的拓扑绝缘状态的出现，并具有一系列Chern数| C | = 4- | V |，其中V是Moiréunite Cell中的电子（孔）数量。当θ> 1.25°时，来自平坦带中的Chern绝缘子消失并演变成一个分形的Hofstadter Butterfly Quantum Hall绝缘子，其中一个Moiré中的磁通量Unite Tym在其中。我们的观察结果将刺激有关电子相互作用与非平凡带拓扑之间关系的进一步理论和实验研究。
Twisting two layers into a magic angle (MA) of ~1.1° is found essential to create low energy flat bands and the resulting correlated insulating, superconducting, and magnetic phases in twisted bilayer graphene (TBG). While most of previous works focus on revealing these emergent states in MA-TBG, a study of the twist angle dependence, which helps to map an evolution of these phases, is yet less explored. Here, we report a magneto-transport study on one non-magic angle TBG device, whose twist angle θ changes from 1.25° at one end to 1.43° at the other. For θ=1.25°, we observe an emergence of topological insulating states at hole side with a sequence of Chern number |C|=4-|v|, where v is the number of electrons (holes) in moiré unite cell. When θ>1.25°, the Chern insulator from flat band disappears and evolves into fractal Hofstadter butterfly quantum Hall insulator where magnetic flux in one moiré unite cell matters. Our observations will stimulate further theoretical and experimental investigations on the relationship between electron interactions and non-trivial band topology.
