Persistent spin texture in tetragonal BiFeO3

Abstract

We report the existence of bulk persistent spin texture in P4mm tetragonal BiFeO3, a ferroelectric with ultrahigh spontaneous polarization. Our density functional theory calculations reveal that tetragonal BiFeO3 exhibits sufficiently strong spin–orbit coupling, yielding a sizable Rashba coefficient of 0.31 eV · Å. More importantly, it is demonstrated that the polarization-induced spin–orbit field is unidirectional on the Z–Γ–X plane which contains the polar axis. Consequently, there emerges a momentum-independent spin texture, allowing a long-lived persistent spin helix with a wavelength of 23 nm in the real space.