Topology-dependent node dynamics under mechanical manipulation in moiré ferroelectrics.

Abstract

Van der Waals moiré superlattices can host interfacial ferroelectric domains, whose arrangement is influenced by the topology of nodes. Here, we investigate the dynamic behavior and topological protection of node types in twisted WSe₂ homobilayers under local mechanical perturbations. Dark-field transmission electron microscopy and Kelvin probe force microscopy reveal symmetric sixfold nodes as well as non-ideal nodes, including fourfold and eightfold types. Mechanical loading with an atomic force microscopy tip shows striking contrasts in node motion: symmetric sixfold nodes are dynamically robust, whereas an asymmetric sixfold node can be displaced and guided by the tip scan direction, as confirmed by quasi-static loading simulations. Furthermore, we observe a fourfold node that fractured due to its lack of topological protection. These findings establish a direct link between node topology and mechanical response, providing fundamental insights into moiré ferroelectricity and advancing our understanding of topological defects in two-dimensional van der Waals materials.