Zheng Fan, Wang Lin-Wang
School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083, China.
Phys Rev Lett. 2023 Oct 13;131(15):156302. doi: 10.1103/PhysRevLett.131.156302.
With the rapid development of ultrafast experimental techniques for the research of carrier dynamics in solid-state systems, a microscopic understanding of the related phenomena, particularly a first-principle calculation, is highly desirable. Nonadiabatic molecular dynamics (NAMD) offers a real-time direct simulation of the carrier transfer or carrier thermalization. However, when applied to a periodic supercell, there is no cross-k-point transitions during the NAMD simulation. This often leads to a significant underestimation of the transition rate with the single-k-point band structure in a supercell. In this work, based on the surface hopping scheme used for NAMD, we propose a practical method to enable the cross-k transitions for a periodic system. We demonstrate our formalism by showing that the hot electron thermalization process by the multi-k-point NAMD in a small silicon supercell is equivalent to such simulation in a large supercell with a single Γ point. The simulated hot carrier thermalization process of the bulk silicon is compared with the recent ultrafast experiments, which shows excellent agreements. We have also demonstrated our method for the hot carrier coolings in the amorphous silicons and the GaAlAs_{2} solid solutions with the various cation distributions.
随着用于研究固态系统中载流子动力学的超快实验技术的迅速发展，对相关现象进行微观理解，尤其是进行第一性原理计算，变得非常必要。非绝热分子动力学（NAMD）提供了载流子转移或载流子热化的实时直接模拟。然而，当应用于周期性超胞时，在NAMD模拟过程中不存在跨k点跃迁。这通常会导致使用超胞中单一k点能带结构时跃迁速率被显著低估。在这项工作中，基于用于NAMD的表面跳跃方案，我们提出了一种使周期性系统能够进行跨k跃迁的实用方法。我们通过表明在小硅超胞中通过多k点NAMD进行的热电子热化过程等同于在具有单个Γ点的大超胞中的此类模拟，来展示我们的形式体系。将块状硅的模拟热载流子热化过程与最近的超快实验进行了比较，结果显示出极好的一致性。我们还展示了我们的方法在具有各种阳离子分布的非晶硅和GaAlAs₂固溶体中的热载流子冷却情况。
