Polarity tuning of spin-orbit-induced spin splitting in two-dimensional transition metal dichalcogenides

Abstract

The established spin splitting in a monolayer (ML) of transition metal dichalcogenides (TMDs) induced by inversion symmetry breaking is dictated by mirror symmetry operations to exhibit the fully out-of-plane direction of spin polarization. Through first-principles density functional theory calculations, we show that polarity inducing mirror symmetry breaking leads to sizable spin splitting having in-plane spin polarization. These splittings are effectively controlled by tuning the polarity using biaxial strain. Furthermore, admixtures between the out-of-plane and in-plane spin-polarized states in the strained polar systems are identified, which are expected to influence the spin relaxation through the Dyakonov–Perel mechanism. Our study clarified that polarity plays an important role in controlling the spin splitting and spin relaxation in the TMD ML, which is useful for designing future spintronic devices.