Coexistence of Rashba effect and spin–valley coupling in TiX2 (X = Te, S, and Se) based heterostructures

Abstract

Spin–orbit coupling (SOC) combined with broken inversion symmetry plays a key role in inducing Rashba effect. The combined spontaneous polarization and Rashba effect enables controlling a material's spin degrees of freedom electrically. In this work, we investigated an electronic band structure for several combinations of TiX2 monolayers (X = Te, S, and Se): TiTe2/TiSe2, TiTe2/TiS2, and TiSe2/TiS2. Based on the observed orbital hybridization between the different monolayers in these heterostructures (HSs), we conclude that the most significant Rashba splitting occurs in TiSe2/TiS2. Subsequently, we used fluorine (F) as an adatom over the surface of TiSe2/TiS2 at hollow and top sites of the surface to enhance the Rashba intensity, as the F adatom induces polarization due to the difference in charge distribution. Furthermore, by increasing the number of F atoms on the surface, we reinforced the band splitting, i.e., we observe Rashba splitting accompanied by Zeeman splitting at the valence-band edge states. Berry curvatures at K and K′ with equal and opposite nature confirm the existence of valley polarization. The computationally observed properties suggest that these HSs are promising candidates for spin–valley Hall effect devices and other spintronic applications.