用于跨越动量空间的非平衡激子-声子耦合动力学的从头算含时GW方法
Ab initio time-dependent GW approach for nonequilibrium exciton-phonon coupled dynamics across momentum space
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中文总结 AI 辅助
研究材料非平衡激子-声子耦合动力学面临挑战。提出从头算含时绝热GW方法，纳入全有限动量耦合，可实时模拟。通过研究单层WSe2中激子跃迁验证，揭示其超快能谷间动力学，建立了相关非平衡格林函数框架。
中文摘要 AI 辅助
材料中光激发的动力学通常涉及非平衡态下相互交织的电子-空穴（e-h）和电子-声子（e-ph）相互作用。然而，对这种非平衡动力学进行完整的理论描述需要在整个晶体动量空间实时系统地处理相干激子激发和激子-声子相互作用，这对第一性原理方法来说仍是重大挑战且难以实现。本文提出了一种新的从头算含时绝热GW方法，该方法纳入了全有限动量e-h和e-ph耦合，能够对相干耦合的激子-声子动力学进行实时模拟。通过在时间分辨和角分辨光电子能谱的泵浦-探测装置中研究单层WSe2中的直接到间接激子跃迁，展示了这种新方法的能力。结果表明，该系统中激子通过声子介导的超快能谷间动力学在约0.5 ps内，表现为能隙内光发射强度从K谷转移到Q谷。这项工作建立了一个全面且实用的非平衡格林函数框架，用于从第一性原理精确模拟涉及耦合激子和声子的非平衡和相干激发。
英文摘要
The dynamics of optical excitations in materials generally involves intertwined electron-hole (e-h) and electron-phonon (e-ph) interactions out of equilibrium. However, a full theoretical description of such nonequilibrium dynamics requires a systematic treatment of the coherent excitonic excitations and exciton-phonon interactions across the entire crystal momentum space in real time, which remains a major challenge and out of reach for first-principles approaches. Here, we present a new ab initio time-dependent adiabatic GW methodology that incorporates full finite-momentum e-h and e-ph couplings, enabling real-time simulations of the coherently coupled exciton-phonon dynamics. The excitonic excitations are naturally described by the equation of motion of the interacting single-particle density matrix, whereas their couplings to phonons are formulated within a linear-response framework, hence the simulations can be efficiently carried out within a primitive unit cell. We demonstrate the capabilities of this new approach by investigating the direct-to-indirect exciton transitions in monolayer WSe2 in a pump-probe setup of time-resolved and angle-resolved photoemission spectroscopy. Our results reveal that the phonon-mediated ultrafast intervalley dynamics of excitons of this system is within ~0.5 ps, manifested as in-gap photoemission intensity transfer from the K-valley to the Q-valley. This work establishes a comprehensive and practical nonequilibrium Green's function framework for accurately simulating nonequilibrium and coherent excitations involving coupled excitons and phonons from first principles.
