Band Structure and Spin-Orbital Texture of the (111)-KTaO3 Two-Dimensional Electron Gas

TL;DR

This study investigates the electronic structure and spin-orbital texture of a (111)-oriented 2DEG in KTaO3 using ARPES and theoretical calculations, revealing complex spin textures and large spin-splitting with potential spintronic applications.

Contribution

It provides the first detailed experimental and theoretical analysis of the (111)-oriented KTaO3 2DEG's electronic and spin structure, highlighting its unique anisotropic Rashba effect.

Findings

Multiple sub-bands form a six-fold symmetric Fermi surface.

The Fermi surface originates from bulk J=3/2 states with unconventional spin textures.

The spin-splitting is an order of magnitude larger than in SrTiO3.

Abstract

Two-dimensional electron gases (2DEGs) in oxides show great potential for discovering new physical phenomena and at the same time hold promise for electronic applications. In this work we use angle resolved photoemission to determine the electronic structure of a 2DEG stabilized in the (111)-oriented surface of the strong spin orbit coupling material KTaO3. Our measurements reveal multiple sub-bands that emerge as a consequence of quantum confinement and form a six-fold symmetric Fermi surface. This electronic structure is well reproduced by self-consistent tight-binding supercell calculations. Based on these calculations we determine the spin and orbital texture of the 2DEG. We show that the 2DEG Fermi surface is derived from bulk J = 3/2 states and exhibits an unconventional anisotropic Rashba-like lifting of the spin-degeneracy. Spin-momentum locking holds only for high symmetry directions and a strong out-of-plane spin component renders the spin-texture three-fold symmetric. We find that the average spin-splitting on the Fermi surface is an order of magnitude larger than in SrTiO3, which should translate into an enhancement in the spin-orbitronic response of (111)-KTaO3 2DEG based devices.