Molecular polaritons arise from electronic or vibrational strong coupling (ESC, VSC) with confined electromagnetic fields. While these have been widely studied, the influence of electron-nuclear dynamics in driven cavities remains largely unknown. Here, we report a previously unrecognized mechanism of vibrational activation that emerges under collective ESC in driven optical cavities. Using simulations that self-consistently combine Maxwell's equations with quantum molecular dynamics, we show that collective electronic Rabi oscillations coherently drive nuclear motion. This effect is captured using both vibrational wave packet dynamics in a minimal two-level model and atomistic simulations based on time-dependent density-functional tight-binding theory. Vibrational activation depends nonmonotonically on the Rabi frequency and is maximized when the collective polaritonic splitting resonates with a molecular vibrational mode. The mechanism exhibits features consistent with a stimulated Raman-like relaxation mechanism. Our predictions are robust under realistic cavity conditions and provide the conditions in which they could be verified experimentally.
Bustamante et al. (Mon,) studied this question.