Coexisting unconventional Rashba- and Zeeman-type spin splitting in Pb-adsorbed monolayer WSe2

Abstract

Based on first-principles calculations, the unconventional Rashba- and Zeeman-type spin splitting can simultaneously coexist in the Pb-adsorbed monolayer WSe₂ system. The first two adsorption configurations t ₁ and t ₂ show remarkable features under the spin–orbit coupling, in which two split energy branches show same spin states at the left or right side of Γ, and the spin polarization is reversed for both Rashba band branches. For the second adsorption configuration, an energy gap was observed near the unconventional spin polarization caused by the repelled Rashba bands for avoid crossing, and this gap can produce non-dissipative spin current by applying the voltage. The results for t ₂ configuration with spin reversal show that the repel band gap and Rashba parameter can be effectively regulated within the biaxial strain range of −8% to 6%. By changing the adsorption distance d between Pb and the neighboring Se atom layer, the reduced d caused the transfer from Rashba-type to Zeeman-type spin splitting. This predicted adsorption system would be promising for spintronic applications.