Proximity exchange effects in excitons of TMDC/ferromagnet van der Waals heterostructures

Proximity effects in two-dimensional van der Waals heterostructures are an efficient way to modify intrinsic electronic properties[1]. In particular, proximity exchange offers the possibility of inducing magnetic properties in nominally nonmagnetic materials. Furthermore, this induced synthetic Zeeman spltting exhibits strong signatures in the optical spectra. Combining ab initio calculations with tight-binding modeling and the effective Bethe-Salpeter equation for excitons, we investigate the proximity exchange in TMDC/ferromagnet systems: (i) (Mo,W)Se2 on the ultrathin van der Waals ferromagnet CrI3[2] and (ii) (Mo,W)S2/hBN on ferromagnets Co and Ni[3]. Since stacking different 2D materials requires adjusting the lattice parameters to obtain commensurate supercells, we also discuss the impact of biaxial strain in monolayer TMDCs[4]. We show the evolution of different optical transitions and the role of excitonic effects in the direct transitions. [1] Zutic et al., Mater. Today 22, 85 (2019). [2] Zollner, Faria Junior, Fabian, PRB 100, 085128 (2019). [3] Zollner, Faria Junior, Fabian, in preparation. [4] Zollner, Faria Junior, Fabian, arXiv:1909.10763 (2019).