Large valley splitting induced by spin-orbit coupling effects in monolayer W 2 NSCl.

Two-dimensional (2D) valley materials are promising materials for writing and storing information. The search for 2D materials with large valley splitting is essential for the development of spintronics and valley electronics. In this study, we theoretically design 2D W 2 NSCl MXenes with large valley splitting based on first-principle calculations. Due to the strong spin-orbit coupling (SOC) and the broken inversion symmetry, the W 2 NSCl monolayer exhibits valley splitting values of 491 meV and 83 meV at K / K ' of the valence and conduction bands, respectively. The valley splitting of W 2 NSCl is robust to biaxial strain. Because of the broken mirror symmetry of W 2 NSCl, there is a Rashba effect at Γ with a Rashba parameter of 1.019 V Å. Based on the maximum localization of the Wannier function, we found the non-zero Berry curvature at K / K '. Furthermore, the non-zero Berry curvature at the K / K ' valley increases monotonically with an external strain from -4% to 4%. Our finding shows that W 2 NSCl is a candidate material for valley electronics and spintronics applications.