Spin-Polarized Two-Dimensional Electron Gas with Giant Rashba Splitting at the EuTiO ₃ /KTaO ₃ (111) Interface under Light Illumination

Abstract 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 a 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)-oriented EuTiO 3 /KTaO 3 (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 × 10 13 cm −2 , highlighting dramatic changes in the band topology of KTO(111) interface. Furthermore, at 2 K, the carrier mobility is enhanced from 103 cm 2 ⋅V −1 ⋅s −1 to 1800 cm 2 ⋅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.