Ab initio time-dependent GW approach for nonequilibrium exciton-phonon coupled dynamics across momentum space

Zhenfa Zheng; Benran Zhang; Jiawei Ruan; Chih-En Hsu; Zien Zhu; Supavit Pokawanvit; Felipe H. da Jornada; Hung-Chung Hsueh; Ting Cao; Mauro Del Ben; Yang-Hao Chan; Steven G. Louie; Zhenglu Li

arXiv · 2607.15411

Ab initio time-dependent GW approach for nonequilibrium exciton-phonon coupled dynamics across momentum space

Zhenfa Zheng·Benran Zhang·Jiawei Ruan·Chih-En Hsu·Zien Zhu·Supavit Pokawanvit·Felipe H. da Jornada·Hung-Chung Hsueh·Ting Cao·Mauro Del Ben·Yang-Hao Chan·Steven G. Louie·Zhenglu Li

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Abstract

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.

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Zhenfa Zheng, Benran Zhang, Jiawei Ruan, Chih-En Hsu, Zien Zhu, Supavit Pokawanvit, Felipe H. da Jornada, Hung-Chung Hsueh, Ting Cao, Mauro Del Ben, Yang-Hao Chan, Steven G. Louie, Zhenglu Li. 2026-07-16. Ab initio time-dependent GW approach for nonequilibrium exciton-phonon coupled dynamics across momentum space. https://arxiv.org/abs/2607.15411

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