Moiré-polaritons in a dark Bose-Einstein condensate.

Quantum mixtures of moiré excitons have arisen as a platform for realizing novel phases of light and matter. Here, we study moiré polaritons coupled to a Bose-Einstein condensate of dark-state excitons confined to a moiré superlattice. We develop a variational approach to analyze the optical response of the system and demonstrate that strong exciton-exciton interactions significantly modify the character of moiré polaritons, leading to the emergence of moiré polaron-polaritons with sizable quasiparticle energy shifts of the avoided crossing between the principal polariton branches, and the emergence of an additional, stable repulsive-polariton bound state.