In stark contrast to the conventional charge density wave (CDW) materials, the one-dimensional CDW on the In/Si(111) surface exhibits immediate damping of the CDW oscillation during the photoinduced phase transition. Here, by successfully reproducing the experimentally observed photoinduced CDW transition on the In/Si(111) surface by performing real-time time-dependent density functional theory (rt-TDDFT) simulations, we demonstrate that photoexcitation promotes valence electrons from Si substrate to empty surface bands composed primarily of the covalent p-p bonding states of the long In-In bonds, generating interatomic forces to shorten the long bonds and in turn drives coherently the structural transition. We illustrate that after the structural transition, the component of these surface bands occurs a switch among different covalent In bonds, causing a rotation of the interatomic forces by about {\pi}/6 and thus quickly damping the oscillations in feature CDW modes. These findings provide a deeper understanding of photoinduced phase transitions.

中文翻译：

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光致电荷密度波跃迁中相干振荡立即阻尼的起源

与传统的电荷密度波 (CDW) 材料形成鲜明对比的是，In/Si(111) 表面上的一维 CDW 在光致相变期间表现出 CDW 振荡的直接阻尼。在这里，通过执行实时时间相关密度泛函理论 (rt-TDDFT) 模拟，成功地再现了实验观察到的 In/Si(111) 表面上的光诱导 CDW 跃迁，我们证明了光激发促进价电子从 Si 衬底变为空表面带主要由长 In-In 键的共价 pp 键态组成，产生原子间力以缩短长键，进而连贯地驱动结构转变。我们说明在结构转变之后，这些表面带的组成部分发生了不同共价 In 键之间的转换，导致原子间力旋转大约 {\pi}/6，从而快速抑制特征 CDW 模式中的振荡。这些发现提供了对光诱导相变的更深入理解。