Phonon Screening and Polaronic Renormalization of Excitons in Semiconductors from First Principles

Exciton-phonon interactions play a significant role in determining the nature and dynamics of photoexcitations in solids and molecular systems, and ab initio many-body perturbation theory provides a rigorous framework for introducing and calculating these effects. However, recent studies extending the conventional ab initio Bethe-Salpeter equation (BSE) approach to include phonons have only selectively included low-order contributions to the exciton–phonon self-energy, leaving open when and how different terms contribute in real materials. Here, we compute low-order contributions to the exciton-phonon self-energy for a few prototypical semiconductors, building on the ab initio BSE approach to capture both dynamical phonon screening and polaronic effects. From our results, we quantify how phonons renormalize the excitonic spectrum and lead to temperature-dependent exciton energies and lifetimes. We compare our calculations with prior results, and we discuss implications for self-trapped exciton formation and for exciton dynamics.