Coupling of MoS2 Excitons with Lattice Phonons and Cavity Vibrational Phonons in Hybrid Nanobeam Cavities

We report resonant Raman spectroscopy of neutral excitons X0 and intravalley trions X- in hBN-encapsulated MoS2 monolayer embedded in a nanobeam cavity. By temperature tuning the detuning between Raman modes of MoS2 lattice phonons and X0/X- emission peaks, we probe the mutual coupling of excitons, lattice phonons and cavity vibrational phonons. We observe an enhancement of X0-induced Raman scattering and a suppression for X - induced, and explain our findings as arising from the tripartite exciton-phonon-phonon coupling. The cavity vibrational phonons provide intermediate replica states of X0 for resonance conditions in the scattering of lattice phonons, thus enhancing the Raman intensity. In contrast, the tripartite coupling involving X- is found to be much weaker, an observation explained by the geometry-dependent polarity of the electron and hole deformation potentials. Our results indicate that phononic hybridization between lattice and nanomechanical modes plays a key role in the excitonic photophysics and light-matter interaction in 2D-material nanophotonic systems.