Strain-tunable ferroelectricity and its control of Rashba effect in KTaO3

Abstract

The effects of epitaxial strain on the ferroelectric, structural properties of KTaO3 are studied by means of first-principles calculations. We show that the ferroelectric polarization magnitude as well as the orientation can be tuned by an in-plane strain: the c-phase is energetically more stable than the aa-phase at a large compressive strain while a phase transition from c- to aa-phase is observed at a large tensile strain, owing to the significant polarization-strain coupling. More importantly, based on relativistic first-principles calculations, we demonstrate a large Rashba spin splitting in the strained KTaO3. Interestingly, the spin textures in momentum space can be controlled and switched via polarization switching. Our tight-binding analysis indicates that the combination of spin-orbit coupling and ferroelectric distortion plays a key role for the observed Rashba spin splitting. Our results present some fundamental understanding of the interplay between Rashba effect and ferroelectricity in oxides and open avenues for nonvolatile spintronic device applications.