Atomically-resolved theory of the magnitude of the bulk Rashba effect

Rashba effect based-mechanisms to control and generate spin-polarized states have been one of the cornerstones of spintronics. A strong Rashba effect -- as measured by the Rashba coefficient α_R -- is required for applications. However, the physical mechanism defining the R scale, i.e., the magnitude of α_R, is unknown. We find an intrinsic separation between strong Rashba effect associated with anti-crossing bands, and weak Rashba effect associated with no anti-crossing bands. As an application of the proposed theory, we use this design principle to guide the selection of strong Rashba compounds. First, we illustrate that since topological insulators (TIs) intrinsically have anti-crossing bands, strong Rashba compounds could then be identified almost effortlessly by isolating TIs that are non-centrosymmetric, thus establishing a case for cross-functionality of topological Rashba materials. Second, we predict 34 strong Rashba materials by performing DFT calculations for ~800 potential Rashba compounds and filtering those with anti-crossing bands. This reveals rationally designed cases including known GeTe and BiTeI, and compounds that were previously made but unnoticed as Rashba compounds BiTeCl (P6₃mc) and BaCdK2Sb2 (Pmc2₁).