Spin-Polarized Two-Dimensional Electron Gas with Giant Rashba Splitting at the EuTiO₃/KTaO₃(111) Interface under Light Illumination*

The two-dimensional electron gas (2DEG) formed at the interface between two oxide insulators provides new opportunities for electronics and spintronics. The broken inversion symmetry at the heterointerface results in Rashba spin-orbit coupling (RSOC) effect that enables the conversion between spin and charge currents. However, conducting oxide interfaces that simultaneously exhibit strong RSOC and high carrier mobility, a combination query for achieving high spin-to-charge inter-conversion efficiencies, remain scarce. Herein, we report a correlated 2DEG with giant Rashba splitting and high electron mobility in (111)-orientated EuTiO₃/KTaO₃ (ETO/KTO) heterostructures under light illumination. Upon light modulation, a unique carrier-dependent giant anomalous Hall effect, the signature of spin-polarized 2DEG, emerges with a sign crossover at a carrier density of approximately 5.0×10¹³ cm^-2, highlighting dramatic changes in the band topology of KTO(111) interface. Furthermore, at 2 K, the carrier mobility is enhanced from 10³ cm²·V^-1·s^-1 to 1800 cm²·V^-1·s^-1, a remarkable enhancement of approximately 20 times. Accompanying with a giant Rashba coefficient α_R up to 360 meV·Å, this high mobility ferromagnetic 5d oxide 2DEG is predicted to achieve a giant spin-to-charge conversion efficiency of λ ~ 10 nm, showing great potential for designing low-power spin-orbitronic devices.