Achieving giant spin-orbit splitting in conduction band of monolayer WS2 via n-p co-doping

Large spin-orbit splitting in the conduction band minimum (CBM) of monolayer transition metal dichalcogenides (TMDs) is in great demand for suppressing the intervalley scattering. Here we propose a new scheme to significantly enhance the spin-orbit splitting at the K point in the CBM of WS2 monolayer, via the n-p co-doping of fluorine and group VA elements (N, P, As and Sb). Based on the first-principles calculations, a giant spin-orbit splitting of 101.86 meV is theorized in the F-Sb co-doped system. This is evidenced to originate from the enhanced spin-orbit interaction, intimately related to the strengthened trigonal prismatic ligand field and the increased asymmetric surface charge. The giant spin-orbit splitting in the CBM can strongly suppress the intervalley scattering, which will enhance the spin-valley coupling and is beneficial for longer spin and valley lifetimes. This theoretical work provides a key to designing the high-performance monolayer TMD-based spintronic devices.