First-principles ultrafast exciton dynamics and time-domain spectroscopies: Dark-exciton mediated valley depolarization in monolayer WSe2
First-principles ultrafast exciton dynamics and time-domain spectroscopies: Dark-exciton mediated valley depolarization in monolayer WSe2
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DOI：
10.1103/physrevresearch.4.043203
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发表时间：
2022-10
影响因子：
4.2
通讯作者：
Hsiao-Yi Chen;D. Sangalli;M. Bernardi
中科院分区：
文献类型：
--
作者：
Hsiao-Yi Chen;D. Sangalli;M. Bernardi
将第一原理电子声子 ($e$-ph) 相互作用与玻尔兹曼方程相结合的计算可以实现超快载流子和声子动力学的研究。然而，在库仑屏蔽较弱的材料中，电子和空穴形成束缚激子，并且它们的散射过程变得相关，这给非平衡物理建模带来了额外的挑战。在这里，我们展示了使用 $ab~initio$ 激子-声子 (ex-ph) 相互作用以及激子玻尔兹曼方程计算超快激子动力学和相关时域光谱。从非平衡激子群开始，我们开发了考虑电子空穴相关性的时域吸收和光发射光谱的模拟。我们使用这种方法来研究单层 WSe$_2$，我们的计算预测了激子弛豫和谷去极化的亚皮秒时间尺度，并揭示了中间暗激子的关键作用。这项工作中引入的方法能够定量描述具有强束缚激子的材料中的非平衡动力学和超快光谱。
Calculations combining first-principles electron-phonon ($e$-ph) interactions with the Boltzmann equation enable studies of ultrafast carrier and phonon dynamics. However, in materials with weak Coulomb screening, electrons and holes form bound excitons and their scattering processes become correlated, posing additional challenges for modeling nonequilibrium physics. Here we show calculations of ultrafast exciton dynamics and related time-domain spectroscopies using $ab~initio$ exciton-phonon (ex-ph) interactions together with an excitonic Boltzmann equation. Starting from the nonequilibrium exciton populations, we develop simulations of time-domain absorption and photoemission spectra that take into account electron-hole correlations. We use this method to study monolayer WSe$_2$, where our calculations predict sub-picosecond timescales for exciton relaxation and valley depolarization and reveal the key role of intermediate dark excitons. The approach introduced in this work enables a quantitative description of nonequilibrium dynamics and ultrafast spectroscopies in materials with strongly bound excitons.