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