Switchable and tunable Rashba-type spin splitting in covalent perovskite oxides

TL;DR

This paper reports a bismuth-based perovskite with a giant, electrically switchable Rashba spin splitting, controllable via ferroelectric polarization and oxygen octahedra breathing modes, offering new avenues for spin-charge conversion devices.

Contribution

It introduces a novel covalent perovskite exhibiting switchable Rashba spin splitting controlled by structural and electronic parameters.

Findings

Giant, electrically switchable Rashba interaction identified.

Rashba amplitude controlled by ferroelectric polarization.

Structural breathing mode influences spin splitting.

Abstract

In transition metal perovskites (ABO3) most physical properties are tunable by structural parameters such as the rotation of the BO6 octahedra. Examples include the N\'eel temperature of orthoferrites, the conductivity of mixed-valence manganites, or the band gap of rare-earth scandates. Since oxides often host large internal electric dipoles and can accommodate heavy elements, they also emerge as prime candidates to display Rashba spin-orbit coupling, through which charge and spin currents may be efficiently interconverted. However, despite a few experimental reports in SrTiO3-based interface systems, the Rashba interaction has been little studied in these materials, and its interplay with structural distortions remain unknown. In this Letter, we identify a bismuth-based perovskite with a giant, electrically-switchable Rashba interaction whose amplitude can be controlled by both the ferroelectric polarization and the breathing mode of oxygen octahedra. This particular structural parameter arises from the strongly covalent nature of the Bi-O bonds, reminiscent of the situation in perovskite nickelates. Our results not only provide novel strategies to craft agile spin-charge converters but also highlight the relevance of covalence as a powerful handle to design emerging properties in complex oxides.