Ultrafast dynamics of exciton- and trion-polaritons in an atomic crystal microcavity

Atomically thin transition metal dichalcogenides (TMDCs) provide an exceptional platform for investigating light–matter interactions, owing to strong quantum confinement and reduced dielectric screening in the monolayer limit. However, elucidating the ultrafast dynamics of exciton and trion polaritons remains challenging. Here, we fabricate a high-quality (high-Q) optical microcavity incorporating a monolayer of MoSe₂ that simultaneously supports both exciton and trion polariton modes. Temperature-dependent angle-resolved reflectance spectroscopy reveals phonon-mediated decoupling of trion polaritons, attributed to their weaker light–matter coupling strength and lower binding energy. Time-resolved photoluminescence (PL) measurements show cavity-induced lifetime compression, leading to comparable emission lifetimes for both polariton species. These findings provide new insights into the dynamics of hybrid light–matter states and suggest a promising route for their manipulation in two-dimensional photonic systems.