Abstract
In this paper we develop the excitonic theory of 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 two in the case of MoS2 in proximity to a Cobalt thin film.
Highlights
Proximity effects have been known for decades [1], but their true potential was only unleashed with the rise of twodimensional (2D) materials [2]
We have studied the effects produced on a MoS2 band structure due to proximity to a cobalt ferromagnetic thin film, the case of MoS2 on a heterostructure composed of MoS2/hexagonal boron nitride (hBN)/Co/quartz was studied
We started using an effective low-energy Hamiltonian, composed of a massive Dirac Hamiltonian, a spin-orbit coupling term, and an exchange contribution, to theoretically describe the changes that the transition metal dichalcogenides (TMDs) band structure undergoes when placed in the vicinity of a ferromagnetic thin film
Summary
Proximity effects have been known for decades [1], but their true potential was only unleashed with the rise of twodimensional (2D) materials [2]. Their thickness can be orders of magnitude inferior to the length scale of those effects This allows the wave function of the material causing the proximity effect to totally engulf the 2D system [4], drastically modifying its intrinsic properties. With the ability to control both the spin and valley degrees of freedom by ingeniously choosing an adequate substrate, we can explore magneto-optical effects, such as the Kerr rotation angle in the absence of magnetic fields. These kind of effects are vastly studied and used in bulk materials [22,23,24], their true potential in 2D materials is yet to be fulfilled. An Appendix gives the transformation of the Bethe-Salpeter equation to real space
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