AML, Department of Engineering Mechanics, Tsinghua University, Beijing, China.
State Key Laboratory of Tribology, Tsinghua University, Beijing, China.
Nat Mater. 2022 Jun;21(6):621-626. doi: 10.1038/s41563-022-01232-2. Epub 2022 Apr 21.
Atomic reconstruction has been widely observed in two-dimensional van der Waals structures with small twist angles. This unusual behaviour leads to many novel phenomena, including strong electronic correlation, spontaneous ferromagnetism and topologically protected states. Nevertheless, atomic reconstruction typically occurs spontaneously, exhibiting only one single stable state. Using conductive atomic force microscopy, here we show that, for small-angle twisted monolayer-multilayer graphene, there exist two metastable reconstruction states with distinct stacking orders and strain soliton structures. More importantly, we demonstrate that these two reconstruction states can be reversibly switched, and the switching can propagate spontaneously in an unusual domino-like fashion. Assisted by lattice-resolved conductive atomic force microscopy imaging and atomistic simulations, the detailed structure of the strain soliton networks has been identified and the associated propagation mechanism is attributed to the strong mechanical coupling among solitons. The fine structure of the bistable states is critical for understanding the unique properties of van der Waals structures with tiny twists, and the switching mechanism offers a viable means for manipulating their stacking states.
在小扭转角的二维范德瓦尔斯结构中，已经广泛观察到原子重构。这种异常行为导致了许多新的现象，包括强电子相关、自发铁磁性和拓扑保护态。然而，原子重构通常是自发发生的，只表现出一个单一的稳定状态。在这里，我们使用导电原子力显微镜表明，对于小角度扭曲的单层-多层石墨烯，存在两种具有不同堆叠顺序和应变孤子结构的亚稳态重构状态。更重要的是，我们证明了这两种重构状态可以可逆地切换，并且这种切换可以以一种不寻常的类多米诺骨牌的方式自发传播。通过晶格分辨导电原子力显微镜成像和原子模拟的辅助，已经确定了应变孤子网络的详细结构，并且将其传播机制归因于孤子之间的强力学耦合。双稳态的精细结构对于理解具有微小扭转的范德瓦尔斯结构的独特性质至关重要，而这种切换机制为操纵它们的堆叠状态提供了可行的方法。
