We report selective coupling between neutral excitons X0, vibrational
phonon modes of a freestanding nanobeam cavity and lattice phonons of a MoS2
monolayer fully encapsulated by hBN. Our experimental findings demonstrate that
the cavity vibrational phonons selectively couple to neutral excitons (X0),
and the coupling to negatively charged trion (X−) being significantly
weaker. We establish this result by studying the lattice temperature induced
broadening of exciton linewidths, where the contribution from the X0-cavity
phonon coupling is clearly observed while the X−-cavity phonon coupling is
not. Furthermore, when the Raman modes of MoS2 lattice phonons A1g and
2LA are tuned into an outgoing resonance with exciton emissions, we observe the
X0-cavity phonon-lattice phonon coupling which inherits the characteristics
rule the of X0-cavity phonon coupling. As a result, X0-induced Raman
scatterings are enhanced, while X−-induced scatterings are suppressed,
revealed by the detuning-dependent Raman intensities and the ratio of
X−/X0 emission intensities. The phonon anharmonicity from the coupling
between cavity vibrational phonons and MoS2 lattice phonons is further
demonstrated by the observed Raman linewidth. Such hybrid couplings between
materials and nanostructures enable the control of phonon-induced processes in
nanophotonic and nanomechanical systems incorporating 2D semiconductors