Rashba effect and enriched spin-valley coupling in GaX / MX2 ( M = Mo, W; X = S, Se, Te) heterostructures

Abstract

Using first-principles calculations, we investigate the electronic properties of the two-dimensional $\mathrm{Ga}X$/${MX}_{2}$ ($M$ = Mo, W; $X$ = S, Se, Te) heterostructures. Orbital hybridization between $\mathrm{Ga}X$ and ${MX}_{2}$ is found to result in Rashba splitting at the valence-band edge around the $\mathrm{\ensuremath{\Gamma}}$ point, which grows for increasing strength of the spin-orbit coupling in the $p$ orbitals of the chalcogenide atoms. The location of the valence-band maximum in the Brillouin zone can be tuned by strain and application of an out-of-plane electric field. The coexistence of Rashba splitting (in-plane spin direction) and band splitting at the $K$ and ${K}^{\ensuremath{'}}$ valleys (out-of-plane spin direction) makes $\mathrm{Ga}X$/${MX}_{2}$ heterostructures interesting for spintronics and valleytronics. They are promising candidates for two-dimensional spin-field-effect transistors and spin-valley Hall effect devices. Our findings shed light on the spin-valley coupling in van der Waals heterostructures.