Nonvolatile control of the Mott transition is a central goal in correlated-electron physics, offering access to fascinating emergent states and great potential for technological applications. Compared to chemical or mechanical approaches, ultrafast optical excitation further promises a path to create and manipulate novel non-equilibrium phases with ultimate spatiotemporal precision. However, achieving a truly nonvolatile electronic phase transition in laser-excited Mott systems remains an elusive challenge. Here, we present a highly robust and reversible method for optical control of the Mott state in van der Waals systems. Specifically, using angle-resolved photoemission spectroscopy, we observe a nonvolatile Mott-to-metallic transition in the ultrafast laser-excited charge density wave (CDW) material 1T-TaSe2. Complementary theoretical calculations reveal that this transition originates from a rearrangement of the interlayer CDW stacking. This new stacking order, formed following the ultrafast quenching of the CDW, circumvents the need for large-scale atomic sliding. Intriguingly, it introduces a significant in-plane component to the electron hopping and effectively reduces the ratio of on-site Coulomb interaction to bandwidth, thereby suppressing the Mott state and stabilizing a metallic phase. Our results establish optical-control of interlayer stacking as a versatile strategy for inducing nonvolatile phase transitions, opening a new route to tailor correlated electronic phases and realize reconfigurable high-frequency devices.
@article{arxiv.2512.21628,
title = {Nonvolatile photoswitching of a Mott state via reversible stacking rearrangement},
author = {Junde Liu and Liwen Su and Pei Liu and Hui Liu and Mojun Pan and Yuchong Zhang and Famin Chen and Yueqian Chen and Zhaoyang Xie and Stefan Mathias and Tianping Ying and Lin Hu and Tian Qian and Xun Shi and Yugui Yao},
journal= {arXiv preprint arXiv:2512.21628},
year = {2025}
}