Theoretical Prediction of Bulk Rashba Effect in Pyroelectric Antiferromagnet BiCoO₃

Rashba effect, a type of spin-momentum locking phenomena, commonly occurs at interfaces or surfaces, while it is nowadays well established that Rashba-like band splitting may also occur in non-centrosymmetric (chiral, polar or ferroelectric) bulk materials. Here we are taking a step further by considering a noncentrosymmetric antiferromagnetic oxide as a playground for bulk Rashba effect. In ferroelectric and antiferromagnetic systems, i.e., multiferroic systems, spin-flipping symmetry operations may exist (such as a mirror symmetry operation) which behave as time-reversal symmetry, thus enforcing two-fold degeneracy at specific high-symmetric points and allowing bulk Rashba effect to emerge. As a prototypical example, ab-initio DFT calculations of antiferromagnetic BiCoO₃ in the polar structure reveal that a large Rashba-like spin splitting occurs at the conduction band bottom, having a large weight from Bi-p orbital states [1]. In this presentation, we also show that the spin texture of such a multiferroic can be modulated by applying a magnetic field.
[1] Kunihiko Yamauchi, Paolo Barone, Silvia Picozzi, arXiv:1910.06758 (Oct2019).