单轴应变双层石墨烯莫尔系统的连续介质模型
The Continuum Model for Uniaxially Strained Bilayer Graphene Moiré Systems
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中文总结 AI 辅助
该研究构建单轴应变AB堆叠双层石墨烯莫尔系统的连续介质模型，揭示临界应变下的拓扑相变，为应变工程调控拓扑输运提供新途径。
中文摘要 AI 辅助
我们构建了一个连续介质模型，用于描述通过沿x方向拉伸一层AB堆叠双层石墨烯至因子s所形成的一维莫尔超晶格。遵循用于扭转双层石墨烯的Bistritzer-MacDonald模型的思路，我们将层间耦合处理为多个狄拉克点之间的跳跃。在临界拉伸因子s≈1.018时，费米能级附近的两个能带发生接触，沿k_y方向形成两个简并点。该能隙闭合伴随拓扑相变，其中陈数从1变为-1，且Berry曲率偶极子的符号发生改变，我们提出这一现象可通过非线性霍尔效应进行探测。我们发现，单轴应变会调制狄拉克谷间耦合，进而驱动带隙坍缩及后续拓扑数反转。这为通过莫尔异质结构的应变工程设计拓扑输运和量子反常霍尔效应开辟了一条途径。
英文摘要
We construct a continuum model for a one-dimensional moiré superlattice formed by stretching one layer of AB-stacked bilayer graphene along the x direction by a factor s. Following the spirit of the Bistritzer-MacDonald model for twisted bilayer graphene, we treat the interlayer coupling as hopping between several Dirac points. At a critical stretch factor s ~ 1.018 the two bands near the Fermi level touch, forming two degeneracy points along the k_y direction. This gap closing is accompanied by a topological phase transition, in which the Chern number changes from 1 to -1, and by a sign change of the Berry-curvature dipole, which we propose can be detected through the nonlinear Hall effect. We find that uniaxial strain modulates inter-Dirac-valley coupling, which drives band gap collapse and subsequent topological number inversion. This opens a route to engineer topological transport and quantum anomalous Hall effects via strain engineering of moiré heterostructures.
