Bauerhenne Bernd, Garcia Martin E
Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Strasse 40, 34132, Kassel, Germany.
Sci Rep. 2024 Dec 31;14(1):32168. doi: 10.1038/s41598-024-83416-1.
The ultrafast ionic dynamics in solids induced by intense femtosecond laser excitation are controlled by two fundamentally different yet interrelated phenomena. First, the substantial generation of hot electron-hole pairs by the laser pulse modifies the interatomic bonding strength and characteristics, inducing nonthermal ionic motion. Second, incoherent electron-ion collisions facilitate thermal equilibration between electrons and ions, achieving a uniform temperature on a picosecond timescale. This article presents a unified theoretical description that effectively integrates both processes. Our method is adaptable for use in both ab-initio simulations and extensive molecular dynamics simulations, extending the conventional two-temperature model to incorporate molecular dynamics equations of motion. To demonstrate the efficacy of our approach, we apply it to the laser excitation of silicon thin films. Our simulations closely match experimental observations, accurately reproducing the temporal evolution of the Bragg peaks.
由强飞秒激光激发引起的固体中的超快离子动力学受两种根本不同但相互关联的现象控制。首先，激光脉冲大量产生热电子 - 空穴对，改变了原子间的键合强度和特性，引发非热离子运动。其次，非相干电子 - 离子碰撞促进了电子与离子之间的热平衡，在皮秒时间尺度上实现了均匀温度。本文提出了一种统一的理论描述，有效地整合了这两个过程。我们的方法适用于从头算模拟和广泛的分子动力学模拟，将传统的双温度模型扩展到包含分子动力学运动方程。为了证明我们方法的有效性，我们将其应用于硅薄膜的激光激发。我们的模拟与实验观测结果紧密匹配，准确地再现了布拉格峰的时间演化。
