Coupled plasmon-phonon modes in monolayer MoS2

We present a theoretical study of the plasmon-phonon coupling in a suspended monolayer MoS2 and a MoS2 substrate system using a diagrammatic self-consistent field theory. The four coupled plasmon-phonon modes and the four plasmon-surface phonon modes are observed due to the spin-orbit and electron-optic phonon interactions. The two of coupled plasmon-phonon and plasmon-surface phonon modes are optic-like and the other two are acoustic-like. The plasmon are strongly coupled with the optic-phonon in MoS2 and the surface optic-phonon in the substrates as the electron density or wave-vector increases. The strong plasmon-phonon coupling shows that the optoelectronic properties of monolayer MoS2 are evidently modulated by electron-phonon interactions. The hybrid plasmon-phonon polaritons can be achieved by strong light-mater interactions. This study is relevant to the application of MoS2 as novel plasmonic and nanophotonic devices.