Transition-metal dichalcogenides for spintronic applications

Spin-orbit splitting in transition-metal dichalcogenide monolayers is investigated on the basis of density-functional theory within explicit two-dimensional periodic boundary conditions. The spin-orbit splitting reaches few hundred meV and increases with the size of the metal and chalcogen atoms, resulting in nearly 500 meV for WTe₂. Furthermore, we find that similar to the band gap, spin-orbit splitting changes drastically under tensile strain. In centrosymmetric transition metal dichalcogenide bilayers, spin-orbit splitting is suppressed by the inversion symmetry. However, it could be induced if the inversion symmetry is explicitly broken, e.g. by a potential gradient normal to the plane, as it is present in heterobilayers (Rashbasplitting). In such systems, the spin-orbit splitting could be as large as for the heavier monolayer that forms heterobilayer. These properties of transition metal dichalcogenide materials suggest them for potential applications in opto-, spin- and straintronics.