First-principles theory of giant Rashba-like spin-splitting in bulk ferroelectrics

TL;DR

This paper develops a first-principles theoretical framework explaining large Rashba-like spin splitting in bulk ferroelectrics, emphasizing the role of orbital composition and the orbital Rashba effect, supported by calculations on GeTe.

Contribution

It introduces a comprehensive first-principles theory linking orbital Rashba effect to spin splitting in ferroelectrics, expanding understanding beyond relativistic effects.

Findings

Large spin splitting depends on band character and atomic spin-orbit coupling.

Orbital Rashba effect explains the observed spin textures.

First-principles calculations on GeTe confirm the model's predictions.

Abstract

Recently large Rashba-like spin splitting has been observed in certain bulk ferroelectrics. In contrast with the relativistic Rashba effect, the chiral spin texture and large spin-splitting of the electronic bands depend strongly on the character of the band and atomic spin-orbit coupling. We establish that this can be traced back to the so-called orbital Rashba effect, also in the bulk. This leads to an additional dependence on the orbital composition of the bands, which is crucial for a complete picture of the effect. Results from first-principles calculations on ferroelectic GeTe verify the key predictions of the model.