Abstract：
The study of moiré engineering started with the advent of van der Waals heterostructures, in which stacking 2D layers with different lattice constants leads to a moiré pattern controlling their electronic properties. The field entered a new era when it was found that adjusting the twist between two graphene layers led to strongly-correlated-electron physics and topological effects associated with atomic relaxation. A twist is now routinely used to adjust the properties of 2D materials. This study investigates a new type of moiré superlattice in bilayer graphene when one layer is biaxially strained with respect to the other-so-called biaxial heterostrain. Scanning tunneling microscopy measurements uncover spiraling electronic states associated with a novel symmetry-breaking atomic reconstruction at small biaxial heterostrain. Atomistic calculations using experimental parameters as inputs reveal that a giant atomic swirl forms around regions of aligned stacking to reduce the mechanical energy of the bilayer. Tight-binding calculations performed on the relaxed structure show that the observed electronic states decorate spiraling domain wall solitons as required by topology. This study establishes biaxial heterostrain as an important parameter to be harnessed for the next step of moiré engineering in van der Waals multilayers.
摘要：
莫尔工程的研究始于范德华异质结构的出现，其中堆叠具有不同晶格常数的二维层导致控制其电子性质的莫尔图案。当发现调整两个石墨烯层之间的扭曲导致与原子弛豫相关的强相关电子物理学和拓扑效应时，该领域进入了一个新时代。现在，Twist通常用于调整二维材料的属性。这里,我们研究了当一层相对于另一层双轴应变时，双层石墨烯中的一种新型莫尔超晶格-所谓的双轴异质应变。扫描隧道显微镜测量揭示了在小的双轴异应变下与新颖的对称破坏原子重建相关的螺旋电子态。使用实验参数作为输入的原子计算表明，在对齐堆叠的区域周围形成了巨大的原子漩涡，以减少双层的机械能。对松弛结构进行的紧密结合计算表明，观察到的电子态按照拓扑结构的要求装饰了螺旋畴壁孤子。这项研究将双轴异质应变确定为重要参数，可用于范德华多层膜的下一步莫尔工程。本文受版权保护。保留所有权利。
