  We theoretically demonstrate the coupling between excitons in 2D
semiconductors and surface plasmons in a thin metal film by means of a surface
acoustic wave (SAW), proving that the generated exciton-plasmon polaritons (or
plexcitons) are in the strong coupling regime. The strain field of the SAW
creates a dynamic diffraction grating providing the momentum match for the
surface plasmons, whereas the piezoelectric field, that could dissociate the
excitons, is cancelled out by the metal. This is exemplified for monolayer
MoS$\mathrm{_{2}}$ and mono- and few-layer black phosphorus on top of a thin
silver layer on a LiNbO$\mathrm{_{3}}$ piezoelectric substrate, providing Rabi
splittings of 100-150 meV. Thus, we demonstrate that SAWs are powerful tools to
modulate the optical properties of supported 2D semiconductors by means of the
high-frequency localized deformations tailored by the acoustic transducers,
that can serve as electrically switchable launchers of propagating plexcitons
suitable for active high-speed nanophotonic applications.
