We elucidate the origin of the ultrashort laser-driven lattice disorder in germanium through nonadiabatic quantum molecular dynamics simulations. The total disorder is dissected into disorder components arising from electron-phonon coupling, covalent bond softening, and ionic thermal activation caused by potential energy surface modification, using which thermal and nonthermal effects are quantified. We find that, although the bond softening effect initially dominates irrespective of the excitation density, the eventual ultrashort laser-driven phase transition involves both the thermal and nonthermal elements in it, with the level of their effects regulated by the electronic excitation density.

中文翻译：

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量化超短激光照射的锗中热和非热对无序的贡献：非绝热量子分子动力学研究

我们通过非绝热量子分子动力学模拟阐明了锗中超短激光驱动的晶格无序的起源。总无序被分解为由电子-声子耦合、共价键软化和势能表面修饰引起的离子热激活产生的无序成分，利用这些成分可以量化热效应和非热效应。我们发现，尽管无论激发密度如何，键软化效应最初都占主导地位，但最终的超短激光驱动相变涉及其中的热元件和非热元件，其效应水平由电子激发密度调节。