Nonperturbative treatment of the SSH model coupled to quantum light

We investigate how an optical cavity can modify electron-phonon coupling in the non-perturbative regime by developing a fully quantum-mechanical treatment of the structural and electronic properties of the Su-Schrieffer-Heeger model coupled to quantum light. We perform numerical calculations using the exact diagonalization method, and assess the effects of the cavity for both the ground and excited states. We show how including correlation between all the constituents of the system (electrons, nuclei, and photons) gives rise to so called phonoritons, and we compare our treatment to an approach based on the Peierls substitution method. Our results highlight some important factors to consider when treating light-matter interactions in the non-perturbative regime.