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

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.