Giant efficiency for charge-to-spin conversion via the electron gas at the LaTiO3+δ/SrTiO3 interface

Spin-to-charge interconversion has been extensively investigated to improve its efficiency of charge-to-spin conversion, realizing magnetic switching by the technique of low-power spin-orbit torque (SOT). The quasi-two-dimensional electron gas (q2DEG) formed at the interface between insulating ${\mathrm{SrTiO}}₃$ (STO) and ${\mathrm{LaTiO}}_{3+\ensuremath{\delta}}$ (LTO) is supposed to possess strong Rashba spin-orbit coupling. Here, we show that a charge current flowing along the LTO/STO interface, which hosts a q2DEG, can efficiently generate a spin current, producing a strong SOT on adjacent NiFe layer as confirmed by spin-torque ferromagnetic resonance. The maximal charge-to-spin conversion efficiency is as large as $\ensuremath{\sim}2.4$ at room temperature, appearing in the NiFe/LTO/STO structure with a LTO thickness of 4 nm. This efficiency is much larger than that of heavy meals. With the decrease of temperature, the conversion efficiency only exhibits a slight decrease, remaining $\ensuremath{\sim}1.5$ at 20 K. The present work reveals the great potential of conducting oxide interface for oxide-based spintronics.