Giant Rashba-like spin-splitting in bulk GeTe

Surfaces are known to induce large Rashba-like spin splitting of electronic bands. A similar effect was observed in certain bulk ferroelectrics. It was found that the spin texture and large spin-splitting of the electronic bands depends strongly on the electric polarization and atomic spin-orbit coupling. We use first-principles-derived tight-binding model to explore the origin of this effect, and trace it to the interference of Wannier functions with unquenched orbital angular momentum on neighboring sites. This leads to an additional dependence on the orbital composition of the bands. The design rules for materials with electric field control of bands are also discussed.