Anisotropic Exciton-Polariton Relaxation and Phonon Bottleneck in Microcavity-Confined Metal Halide Perovskites: Ab Initio Quantum Dynamics

We developed an <i>ab initio</i> quantum dynamics approach to investigate the evolution of excitons-polaritons coupled to vibrations, combining time-dependent density functional theory, the Pauli-Fierz model, and nonadiabatic molecular dynamics. By applying the approach to a layered lead-halide perovskite, we demonstrated strong dependence of exciton evolution on cavity photon. Hot exciton relaxation is slowed down because nonadiabatic coupling is decreased by the photon component and the coupling matrix changes structure. In contrast, relaxation to the lowest energy exciton is accelerated, breaking the phonon bottleneck, due to a strong, near-resonance interaction with the cavity photon. Anisotropy of light-matter interaction for photon polarization parallel and perpendicular to the perovskite controls how fast hot excitons access the hybrid exciton-polariton manifold. The developed approach provides a means to model quantum dynamics in optical cavities at the <i>ab initio</i> level. The findings demonstrate that anisotropic light-matter coupling can control exciton-polariton dynamics and transport in microcavity-confined low-dimensional materials.