Direct visualization of Rashba-split bands and spin/orbital-charge interconversion at KTaO$_3$ interfaces

TL;DR

This study directly visualizes Rashba-split bands in KTaO$_3$-based 2DEGs, revealing complex spin-orbital textures and high interconversion efficiencies, advancing understanding and design of oxide spintronic interfaces.

Contribution

It provides the first direct visualization of Rashba-split bands in oxide 2DEGs and offers insights into their complex spin-orbital textures and interconversion efficiencies.

Findings

Rashba-split bands confirmed via ARPES in KTaO$_3$-2DEGs.

Unconventional spin and orbital textures with compensation effects.

Predicted interconversion efficiencies surpass other oxide 2DEGs.

Abstract

Rashba interfaces have emerged as promising platforms for spin-charge interconversion through the direct and inverse Edelstein effects. Notably, oxide-based two-dimensional electron gases (2DEGs) display a large and gate-tunable conversion efficiency, as determined by transport measurements. However, a direct visualization of the Rashba-split bands in oxide 2DEGs is lacking, which hampers an advanced understanding of their rich spin-orbit physics. Here, we investigate KTaO$_3$-2DEGs and evidence their Rashba-split bands using angle resolved photoemission spectroscopy. Fitting the bands with a tight-binding Hamiltonian, we extract the effective Rashba coefficient and bring insight into the complex multiorbital nature of the band structure. Our calculations reveal unconventional spin and orbital textures, showing compensation effects from quasi-degenerate band pairs which strongly depend on in-plane anisotropy. We compute the band-resolved spin and orbital Edelstein effects, and predict interconversion efficiencies exceeding those of other oxide 2DEGs. Finally, we suggest design rules for Rashba systems to optimize spin-charge interconversion performance.