  Monolayered MoSe2 is a promising new material to investigate advanced
light-matter coupling as it hosts stable and robust excitons with comparably
narrow optical resonances. In this work, we investigate the evolution of the
lowest lying excitonic transition, the so-called A-valley exciton, with
temperature. We find a strong, phonon-induced temperature broadening of the
resonance, and more importantly, a reduction of the oscillator strength for
increased temperatures. Based on these experimentally extracted, temperature
dependent parameters, we apply a coupled oscillator model to elucidate the
possibility to observe the strong coupling regime between the A-exciton and a
microcavity resonance in three prototypical photonic architectures with varying
mode volumes. We find that the formation of exciton-polaritons up to ambient
conditions in short, monolithic dielectric and Tamm-based structures seems
feasible. In contrast, a temperature-induced transition into the weak coupling
regime can be expected for structures with extended effective cavity length.
Based on these findings, we calculate and draw the phase diagram of polariton
Bosonic condensation in a MoSe2 cavity.

Mesoscale and Nanoscale Physics