Physics Department - Non-equilibrium Exciton Dynamics in Solids: A First-Principles Perspective
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Abstract
Understanding nonequilibrium quasiparticle dynamics in materials requires going beyond static electronic structure. Here, we present an ab initio framework that combines GW/BSE with real-time quantum dynamics to simulate exciton dynamics in different materials. It is shown that exciton dynamics is fundamentally driven by different many-body interactions. In transition metal dichalcogenides, exchange interaction enables ultrafast valley depolarization by opening intervalley channels forbidden in a single-particle picture. Furthermore, phonons act as a dynamical switch that activates long-range Coulomb coupling, leading to rapid bright-to-dark exciton relaxation. When electron-phonon coupling are strong enough, it can also dress the exciton and form polaron-exciton in polar materials. We reveal the formation of dynamically fluctuating polaron–exciton states in TiO₂, where electron–phonon coupling and Coulomb interaction cooperatively determine the quasiparticle properties and lifetimes.
Jin Zhao is a Professor of Physics at the University of Science and Technology of China. Her research focuses on ab initio investigations of excited carrier dynamics in condensed matter systems. By combining many-body perturbation theory with molecular dynamics, she develops and applies the Hefei-nonadiabatic molecular dynamics (Hefei-NAMD) code to model coupled ultrafast charge, spin, and lattice interactions in quantum and condensed matter materials. Her honors include the National Science Fund for Distinguished Young Scholars (2021), the China Young Female Scientist Award (2023), election as a Fellow of the American Physical Society (APS fellow 2023), and the Xplorer Prize (2025).