近日，美国斯坦福大学Liu, Fang团队研究了超晶格的光致扭转与解扭。该研究于2025年11月12日发表在《自然》杂志上。

二维莫尔材料通过人工堆叠原子级薄单层构成。通过精确选择堆叠几何构型，可人工构筑关联与拓扑量子物态。这些定制化的电子特性关键取决于层间耦合与原子对准关系。当前核心科学问题是：原子对准结构如何在超快时间尺度上响应光激发，以及能否动态重构莫尔几何以实时调控涌现现象。

研究组通过超快电子衍射直接观测到，飞秒光激发可驱动2°与57°转角WSe2/MoSe2异质双层中莫尔超晶格产生相干扭转-回弹运动。在带隙以上光激发条件下，莫尔超晶格衍射特征在1皮秒内增强，随后数皮秒后显著抑制，与典型光致晶格热效应截然不同。基于样品动力学模拟的动力学衍射分析表明，局部转角呈现0.6°的峰谷调制幅度，该运动与亚太赫兹频率的莫尔声子相关联。这种动力学由超快电荷转移驱动引发的层间吸引力瞬态增强所主导。该研究为调控莫尔周期晶格畸变及关联局域莫尔势（该势场主导激子、极化子及相关驱动行为）提供了超快操控新路径。

附：英文原文

Title: Photoinduced twist and untwist of moiré superlattices

Author: Duncan, Cameron J. R., Johnson, Amalya C., Maity, Indrajit, Rubio, Angel, Gordon, Matthew, Bartnik, Adam C., Kaemingk, Michael, Li, William H., Andorf, Matthew B., Pennington, Chad A., Bazarov, Ivan V., Tate, Mark W., Muller, David A., Thom-Levy, Julia, Gruner, Sol. M., Lindenberg, Aaron M., Maxson, Jared M., Liu, Fang

Issue&Volume: 2025-11-12

Abstract: Two-dimensional moiré materials are formed by artificially stacking atomically thin monolayers. Correlated and topological quantum phases can be engineered by precise choice of stacking geometry1,2,3. These designer electronic properties depend crucially on interlayer coupling and atomic registry4,5. An open question is how the atomic registry responds on ultrafast timescales to optical excitation and whether the moiré geometry can be dynamically reconfigured to tune emergent phenomena in real time. Here we show that femtosecond photoexcitation drives a coherent twist–untwist motion of the moiré superlattice in 2° and 57° twisted WSe2/MoSe2 heterobilayers, resolved directly by ultrafast electron diffraction. On above-band-gap photoexcitation, the moiré superlattice diffraction features are enhanced within 1ps and subsequently suppressed several picoseconds after, deviating markedly from typical photoinduced lattice heating. Kinetic diffraction analysis, supported by simulations of the sample dynamics, indicates a peak-to-trough local twist angle modulation of 0.6°, correlated with a sub-THz frequency moiré phonon. This motion is driven by ultrafast charge transfer that transiently increases interlayer attraction. Our results could lead to ultrafast control of moiré periodic lattice distortions and, by extension, the local moiré potential that shapes excitons, polarons and correlation-driven behaviours.

DOI: 10.1038/s41586-025-09707-3

Source: https://www.nature.com/articles/s41586-025-09707-3