Nonlinear Freezing of Vibrational Polariton Transport via Mesoscale Simulations.

Two-dimensional real-space imaging of vibrational polariton transport in planar Fabry-Pérot microcavities is numerically simulated via the mesoscale cavity molecular dynamics approach, which self-consistently propagates∼2×104 realistic molecular simulation cells on a two-dimensional grid coupled to the same number of cavity modes. Beyond the well-known polariton ballistic-to-diffusive turnover in the linear response regime, these atomistic simulations reveal a nonlinear freezing mechanism of vibrational polariton transport; that is, under strong pumping of the upper polariton, the initially ballistically propagating upper polariton completely freezes and localizes energy to molecules at specific locations. This mechanism originates from pump-induced breaking of the in-plane translation symmetry: significant molecular excitations at the pulse hot spot broaden the polariton density of states, thus funneling population to the k∥ → 0 band edge with vanishing group velocities. Overall, our work provides numerical insights for exploring novel mechanisms of vibrational polaritons.