Electric fields-tuning plasmon and coupled plasmon-phonon modes in monolayer transition metal dichalcogenides

We theoretically investigate the electric field-tuning plasmons and plasmon-phonon couplings of two-dimensional (2D) transition metal dichalcogenides (TMDs), such as monolayer MoS2, under the consideration of spin-orbit coupling. It is revealed that the frequencies of plasmons and coupled plasmon-phonon modes originating from electron-electron and electron-phonon interactions can be effectively changed by using applied driving electric fields. Notably, these frequencies exhibit a decreasing trend with an increasing electric field. Moreover, the weak angular dependence of these modes suggests that the driving electric field does not induce significant anisotropy in the plasmon modes. The outcomes of this work demonstrate that the plasmon and coupled plasmon-phonon modes can be tuned not only by manipulating the electron density via the application of a gate voltage but also by tuning the applied driving electric field. These findings hold relevance for facilitating the application of 2D TMDs in optoelectronic devices.