Ab initio study of electronic excitations and the dielectric function in molybdenum disulfide monolayer

摘要

The propagator of the induced dynamically screened Coulomb interaction Wind(Q, omega, z, z') is calculated for the MoS2 monolayer. The energy-loss rate of a point charge placed near the MoS2 monolayer is calculated (using the spatial resolution of the Wind in the direction perpendicular to the MoS2 plane) and successfully compared with very recent electron-energy-loss spectroscopy measurements of Hong et al. [J. Hong et al., Phys. Rev. B 93, 075440 (2016)]. The induced propagator Wind, compared with its classical analogous propagator, is used to determine the effective dielectric function epsilon(eff)(omega) of atomically thick crystals. It is shown that epsilon(eff)(omega) extracted from Wind is in good agreement with the dielectric function of the MoS2 extracted from the ellipsometry measurements. A recently proposed method for calculation of the dielectric tensor in quasi-two-dimensional crystals is used to calculate the parallel epsilon(parallel to)(omega) and perpendicular epsilon(perpendicular to)(omega) dielectric functions in MoS2, which are compared with some previous measurements and calculations.