Strain-controlled spin splitting in the conduction band of monolayer WS2

Spin splitting bands that arise in the conduction band minimum (CBM) of the WS2 monolayer (ML) play an important role in the spin-orbit phenomena such as spin-valley coupled electronics. However, application of strain strongly modifies electronic properties of the WS2 ML, which is expected to significantly affect the properties of the spin splitting bands. Here, by using fully-relativistic first-principles calculations based on density-functional theory, we show that a substantial spin splitting band observed in the CBM is effectively controlled and tuned by applying the biaxial strain. We also find that these spin splitting bands induce spin textures exhibiting fully out-of-plane spin polarization in the opposite direction between the K and Q points and their time reversals in the first Brillouin zone. Our study clarifies that the strain plays a significant role in the spin-orbit coupling of the WS2 ML, which has very important implications in designing future spintronics devices.