Band Structure and Spin-Orbital Texture of the (111)-KTaO3 2D Electron Gas

2D electron gases (2DEGs) in oxides show great potential for the discovery of new physical phenomena and at the same time hold promise for electronic applications. In this work, angle-resolved photoemission is used to determine the electronic structure of a 2DEG stabilized in the (111)-oriented surface of the strong spin-orbit coupling material KTaO3. The measurements reveal multiple sub-bands that emerge as a consequence of quantum confinement and form a sixfold symmetric Fermi surface. This electronic structure is well reproduced by self-consistent tight-binding supercell calculations. Based on these calculations, the spin and orbital texture of the 2DEG is determined. It is found 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 threefold symmetric. It is found 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.