Anomalous dispersion of microcavity trion-polaritons

A study of the strong coupling of different exciton species in two-dimensional molybdenum diselenide in a cavity uncovers the rich many-body physics and may lead to new devices. The strong coupling of excitons to optical cavities has provided new insights into cavity quantum electrodynamics as well as opportunities to engineer nanoscale light–matter interactions 1 , 2 , 3 , 4 , 5 , 6 . Here we study the interaction between out-of-equilibrium cavity photons and both neutral and negatively charged excitons, by embedding a single layer of the atomically thin semiconductor molybdenum diselenide in a monolithic optical cavity based on distributed Bragg reflectors. The interactions lead to multiple cavity polariton resonances and anomalous band inversion for the lower, trion-derived, polariton branch—the central result of the present work. Our theoretical analysis reveals that many-body effects in an out-of-equilibrium setting result in an effective level attraction between the exciton-polariton and trion-polariton accounting for the experimentally observed inverted trion-polariton dispersion. Our results suggest a pathway for studying interesting regimes in quantum many-body physics yielding possible new phases of quantum matter 7 , 8 , 9 , 10 , 11 as well as fresh possibilities for polaritonic device architectures 12 , 13 , 14 , 15 .