Origin of Rashba-Dresselhaus effect in a Pb-free ferroelectric nitride perovskite.

First principles electronic structure calculations have been employed to investigate the Rashba-Dresselhaus spin splitting of the bands in a Pb-free non-toxic ferroelectric nitride perovskite. Our first principles results are supplemented with effective k.p model analysis. A systematic study of orthorhombic and rhombohedral phases of this system reveal the importance of symmetry in realizing the nature of the splitting of bands around the time reversal invariant k-points. In the orthorhombic structure it shows linear Rashba-Dresselhaus splitting where nonsymmorphic symmetries play an important role in enhancing the band splitting in the k_z = π/c plane. While the rhombohedral phase shows existence of unique higher order Rashba-Dresselhaus term which mixes with the linear Rashba-Dresselhaus term to produce unusual pattern of out-of-plane spin component in the spin texture that may find application in spintronics.