We develop an ab initio nonadiabatic molecular dynamics (NAMD) method based on GW plus real-time Bethe-Salpeter equation (GW + rtBSE-NAMD) for the spin-resolved exciton dynamics. From investigations on MoS₂, we provide a comprehensive picture of spin-valley exciton dynamics where the electron-phonon (e-ph) scattering, spin-orbit interaction (SOI), and electron-hole (e-h) interactions come into play collectively. In particular, we provide a direct evidence that e-h exchange interaction plays a dominant role in the fast valley depolarization within a few picoseconds, which is in excellent agreement with experiments. Moreover, there are bright-to-dark exciton transitions induced by e-ph scattering and SOI. Our study proves that e-h many-body effects are essential to understand the spin-valley exciton dynamics in transition metal dichalcogenides and the newly developed GW + rtBSE-NAMD method provides a powerful tool for exciton dynamics in extended systems with time, space, momentum, energy, and spin resolution.

我们开发了一种基于GW加上实时Bethe-Salpeter方程（GW + rtBSE-NAMD）的从头算非绝热分子动力学（NAMD）方法，用于自旋分辨激子动力学。来自对MoS _2的调查，我们提供了自旋谷激子动力学的综合图景，其中电子-声子（e-ph）散射，自旋轨道相互作用（SOI）和电子-空穴（eh）相互作用共同起作用。特别是，我们提供了直接的证据，证明在几个皮秒内eh交换相互作用在快速谷底去极化中起着主导作用，这与实验非常吻合。此外，存在由e-ph散射和SOI引起的明暗激子跃迁。我们的研究证明，多体效应对于理解过渡金属二硫化碳中的自旋谷激子动力学是必不可少的，而新开发的GW + rtBSE-NAMD方法为扩展系统随时间，空间，动量，能量和旋转分辨率。