Trion-polaritons in the Ultra-strong coupling regime

Trion-polaritons in two-dimensional semiconductors resulting from the hybridisation of charged excitons with cavity photons are a promising venue for the realization of strong polariton interactions and many-body phases of polaritons. Here, we study trion-polariton in the ultra-strong regime of the light-matter coupling. We develop a systematic theory that permits the simultaneous study of exciton-polaritons in the ultra-strong coupling regime and Feshbach physics. Our results and approach can pave the way for further studies and experiments of exciton-polaritons and Feshbach physics beyond the strong-coupling regime of light and matter.