Rhenium disulfide with a distorted crystal structure has recently attracted tremendous attention for its excitonic and highly anisotropic properties. While ultrafast spectroscopies have extensively probed the carrier response to photoexcitation, the associated lattice response has remained elusive. In this study, we utilize MeV femtosecond electron diffraction to unravel the intricate dynamics of lattice responses and energy flow post-photoexcitation. Combining with structure factor calculations, our investigation reveals the dominance of photoinduced shortening in the Re–Re metallic bond, driven by the strong electron–phonon coupling via the Ag8 mode, resulting in an anisotropic intensity change of Bragg reflections within the initial 0.2 ps. Subsequent stretching of the metallic bond, coupled with the concurrent lattice thermalization, enables the system to reach a new equilibrium within 20 ps. This comprehensive understanding of lattice responses in a nonequilibrium state provides unique insights into photoinduced dynamics in 1T′-ReS2 from a structural perspective.

中文翻译：

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飞秒电子衍射揭示 1T′-ReS2 中金属键的光致缩短

具有扭曲晶体结构的二硫化铼最近因其激子和高度各向异性的特性而引起了极大的关注。虽然超快光谱已广泛探讨了载流子对光激发的响应，但相关的晶格响应仍然难以捉摸。在这项研究中，我们利用 MeV 飞秒电子衍射来揭示晶格响应和光激发后能量流的复杂动力学。结合结构因子计算，我们的研究揭示了 Re-Re 金属键中光致缩短的主导作用，这是由 Ag8 模式的强电子-声子耦合驱动的，导致布拉格反射在初始 0.2 ps 内发生各向异性强度变化。随后金属键的拉伸，加上同时发生的晶格热化，使系统能够在 20 ps 内达到新的平衡。这种对非平衡态晶格响应的全面理解为从结构角度了解 1T'-ReS2 的光致动力学提供了独特的见解。