Excitonic magneto-optical Kerr effect in two-dimensional transition metal dichalcogenides induced by spin proximity

In this paper, we develop the excitonic theory of the Kerr rotation angle in a two-dimensional (2D) transition metal dichalcogenide at zero magnetic field. The finite Kerr angle is induced by the interplay between spin-orbit splitting and proximity exchange coupling due to the presence of a ferromagnet. We compare the excitonic effect with the single-particle theory approach. We show that the excitonic properties of the 2D material lead to a dramatic change in the frequency dependence of the optical response function. We also find that the excitonic corrections enhance the optical response by a factor of 2 in the case of ${\mathrm{MoS}}₂$ in proximity to a cobalt thin film.