The propagator of the induced dynamically screened Coulomb interaction is calculated for the monolayer. The energy-loss rate of a point charge placed near the monolayer is calculated (using the spatial resolution of the in the direction perpendicular to the 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 , compared with its classical analogous propagator, is used to determine the effective dielectric function of atomically thick crystals. It is shown that extracted from is in good agreement with the dielectric function of the 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 and perpendicular dielectric functions in , which are compared with some previous measurements and calculations.

Vito Despoja, Zoran Rukelj, and Leonardo Marušić