Nonlocal Spin-Charge Conversion in (111) and (100) Oriented SrTiO₃ 2D Electron Systems

Complex oxide two-dimensional electron systems provide a versatile platform for studying spin current generation and detection relevant to next-generation spin-orbitronic devices. Among these, SrTiO₃ (STO) interfaces are promising due to their high mobility and strong Rashba effect, which enable long spin diffusion lengths. Using an all-electrical technique, spin transport was measured in two-dimensional electron gases formed at conducting STO (111) and (100) interfaces with amorphous oxide overlayers. A charge current applied through the injection channel generates a transverse spin current through the spin Hall effect, while an adjacent probe converts the spin current into a measurable nonlocal charge current via the inverse spin Hall effect. By varying the probe spacing and applying an external magnetic field, nonlocal voltage responses were detected up to 10 μm away from the injection channel for both crystallographic orientations in high-mobility (>20,000 cm² V⁻¹ s⁻¹) interfaces. The comparative behavior of the (111) and (100) systems highlights the role of crystal symmetry in governing spin transport in complex oxide two-dimensional electron systems.