Anisotropic Rashba-Edelstein Effect in an Oxide 2DEG

Spin-orbit coupling (SOC), which bridges spin and orbital degrees of freedom in electronic states, is the essential ingredient in modern spintronics. In a two-dimensional electron gas (2DEG) without inversion symmetry SOC can induce an anti-symmetric spin texture in momentum space, resulting in a non-equilibrium spin density under an applied electric field – also known as the Rashba-Edelstein Effect (REE). While REE is often considered to be isotropic, an anisotropic Fermi surface, or a symmetry-dictated anisotropic spin-texture, can both lead to an anisotropic REE. We present an observation of anisotropic REE in 2DEGs formed at the KTaO₃ (110) interface, with nominally C_2v symmetry. We have carried out Harmonic Hall measurements to reveal a uniaxial anisotropy in the field-like spin-orbit torque. Our results are consistent with a uniaxial spin texture in 2DEGs formed at the KTaO₃ (110) interface. We will discuss possible origins of this spin texture, including the role of orbital degeneracies and quantum confinement. Our work seeks to deepen our understanding of the origins of spin-texture in multi-orbital systems, and their resulting consequences in spintronic devices.