Breaking Rotational Symmetry in Supertwisted WS 2 Spirals via Moiré Magnification of Intrinsic Heterostrain

作者：Penghong Ci, Yuzhou Zhao, Muhua Sun, Yoonsoo Rho, Yabin Chen, Costas P. Grigoropoulos, Song Jin, Xiaoguang Li, Junqiao Wu · 发表于：Nano Letters · 年份：2022 · DOI：10.1021/acs.nanolett.2c03347 · 被引用次数：36 · 研究领域：2D Materials and Applications、Mechanical and Optical Resonators、Topological Materials and Phenomena

High Resolution Image Download MS PowerPoint Slide Twisted stacking of van der Waals materials with moiré superlattices offers a new way to tailor their physical properties via engineering of the crystal symmetry. Unlike well-studied twisted bilayers, little is known about the overall symmetry and symmetry-driven physical properties of continuously supertwisted multilayer structures. Here, using polarization-resolved second harmonic generation (SHG) microscopy, we report threefold ( C 3 ) rotational symmetry breaking in supertwisted WS 2 spirals grown on non-Euclidean surfaces, contrasting the intact symmetry of individual monolayers. This symmetry breaking is attributed to a geometrical magnifying effect in which small relative strain between adjacent twisted layers (heterostrain), verified by Raman spectroscopy and multiphysics simulations, generates significant distortion in the moiré pattern. Density-functional theory calculations can explain the C 3 symmetry breaking and unusual SHG response by the interlayer wave function coupling. These findings thus pave the way for further developments in the so-called “3D twistronics”.