Hierarchical spin-orbital polarisation of a giant Rashba system

TL;DR

This study reveals that in giant Rashba systems like BiTeI, spin-split bands also develop distinct orbital textures, requiring a new interpretation of spin splitting and offering new control avenues via orbital manipulation.

Contribution

It demonstrates that Rashba spin-split bands in BiTeI have separate orbital textures coupled to different spins, challenging traditional views and suggesting new control mechanisms.

Findings

Spin-split bands in BiTeI have distinct orbital textures.

Orbital textures are coupled to specific spin configurations.

Results require re-interpretation of Rashba spin splitting.

Abstract

The Rashba effect is one of the most striking manifestations of spin-orbit coupling in solids, and provides a cornerstone for the burgeoning field of semiconductor spintronics. It is typically assumed to manifest as a momentum-dependent splitting of a single initially spin-degenerate band into two branches with opposite spin polarisation. Here, combining polarisation-dependent and resonant angle-resolved photoemission measurements with density-functional theory calculations, we show that the two "spin-split" branches of the model giant Rashba system BiTeI additionally develop disparate orbital textures, each of which is coupled to a distinct spin configuration. This necessitates a re-interpretation of spin splitting in Rashba-like systems, and opens new possibilities for controlling spin polarisation through the orbital sector.