Coupling of excitons and photons in optical waveguides and cavities to realize polaritons has provided insights into light-matter interactions from the classical to the quantum regimes, generated new opportunities for engineering optical nonlinearities, and enabled novel technologies. Polaritons have also opened up new pathways to explore highly correlated many-body states of matter. In doped two-dimensional semiconductors, excitons and trions are not independent excitations but are strongly coupled as a result of Coulomb interactions. When excitons in such a material are also strongly coupled with light inside an optical waveguide, the resulting polariton states are coherent superpositions of exciton, trion, and photon states. We realize these exciton-trion-polaritons by coupling an electron-doped monolayer of two-dimensional material MoSe2 to the optical mode in a photonic crystal waveguide. The optical and Coulomb couplings among the excitons, trions, and photons result in three polariton bands. Our theoretical model, based on a many-body description of these polaritons, reproduces the measured polariton energy band dispersions and the energy splittings among the polariton bands with good accuracy. Our work not only sheds light on the nature of highly correlated many body exciton and trion states in doped semiconductors, but is also expected to open up new avenues for device technologies and for realizing optical nonlinearities
Published : "arXiv Mesoscale and Nanoscale Physics".