Plasmon Dispersion in Two-Dimensional Systems with Non-Coulomb Interaction

We theoretically study plasmon dispersion within the random-phase approximation in two-dimensional systems, including undoped and doped monolayer graphene at zero and finite temperatures, and hole- and electron-doped monolayer XSe (X=In,Ga) and disordered two-dimensional electron gas at zero temperature, in the presence of a non-Coulomb interaction of the form ∼r−η. Our findings show that the parameter η, which characterizes the non-Coulombic nature of the interaction, strongly affects the dependence of the plasmon frequency on the wave vector in the long-wavelength limit. Furthermore, the carrier density dependence of the plasmon frequency is unaffected by the parameter η in this regime. For η=1, corresponding to the Coulomb case, the well-known results are fully recovered for all systems studied here.