Electrical control of Rashba effect in a soft-paraelectric system

Ferroelectric Rashba semiconductors (FERSC) are promising materials candidates for spintronic applications. Their intrinsic, electrically-switchable ferroelectric polarizations enable electrical manipulation of spin currents through the Rashba spin-orbit coupling effect, which emerges in crystals with net electrostatic dipoles. However, the condition of ferroelectricity is very strict and limits the choices of materials significantly. In this study, we expand the search range of candidate semiconductors with electrically-controllable Rashba effect to include soft-paraelectric materials (i.e. paraelectric materials with large dielectric susceptibility), and focus on an wide-gap, incipient ferroelectric perovskite system, potassium tantalate KTaO₃. By using a combined first-principles and group theoretical method, we show that in bulk KTaO₃, the Rashba effect strengths and spin patterns of the spin-split bands are controllable through changing the electrostatic polarization magnitudes and directions.