A study of the Rashba effect in two-dimensional ternary compounds ABC monolayers (A = Sb, Bi; B = Se, Te; C = Br; I).

The structure and electronic and spintronic properties of two-dimensional (2D) ternary compounds ABC (A = Sb, Bi; B = Se, Te; C = Br; I) monolayers are investigated using the first-principles method. The ABC monolayers possess typical Janus structures with a considerable potential gradient normal to the surface, inducing intrinsic Rashba spin splitting (RSS) at the conduction band minimum near the Γ point. Among them, the splitting strength of the BiSeI monolayer is the largest and its Rashba coefficient can reach 1.84 eV Å. The projected energy band of the BiSeI monolayer suggests that the RSS state is mainly rooted in the Bi-p z orbital. The RSS strength can be modulated by applying the in-plane strain. The tensile strain can improve the RSS strength, which is ascribed to the increase of the potential gradient normal to the surface. These results indicate that these 2D ternary compounds have great potential for application in tunable spintronic devices.