Optical properties of monolayer NbS2 suspensions

Abstract

We present a theory for the anisotropic optical and magnetic properties of monolayer NbS2 platelets suspended in water and oriented in a magnetic field. We compare experimental data obtained by Liu and Frindt and calculated properties using a dielectric function obtained from a Drude–Lorentz fit to reflectivity data for the bulk material. The anisotropic magnetic susceptibility of the material allows a separate study of the extinction coefficients of light with polarizations perpendicular and parallel to the flake plane. We estimate the contributions from scattering and absorption using the fitted dielectric constant; and we find that for monolayer flakes, absorption should be the dominant mechanism. We also estimate the effects of local-field corrections on absorption and scattering to be small. A puzzling feature is that the experimental ratio of the optical anisotropy for the extinction coefficients fails to satisfy a predicted 2:1 ratio suggested by symmetry considerations.