Exciton Dynamics in 2D Semiconductors Revealed by GW+Realtime-BSE Simulations

Excitons play a central role in determining the optical and transport properties of two-dimensional semiconductors. To capture their nonequilibrium behavior beyond the single-particle picture, we have developed a GW+realtime Bethe–Salpeter equation (GW+realtimeBSE) framework by integrating many-body perturbation theory with real-time nonadiabatic molecular dynamics. This approach enables direct simulation of exciton relaxation dynamics with full inclusion of electron–hole interactions. By applying this method to prototypical systems such as MoS₂ and TiO₂, we reveal that many-body electron–hole interactions open additional relaxation pathways that markedly accelerate the redistribution of exciton populations from high-lying to low-lying excitonic states. These results provide microscopic insights into ultrafast energy relaxation in low-dimensional systems and offer a predictive framework for manipulating excitonic processes in emerging quantum and optoelectronic materials.