Spin-charge interconversion in KTaO$_3$ two-dimensional electron gases

TL;DR

This paper reports the first observation of direct and inverse Edelstein effects in a KTaO3-based two-dimensional electron gas, demonstrating efficient spin-charge interconversion and potential for spin-orbitronic device applications.

Contribution

It demonstrates spin-charge interconversion effects in KTaO3 2DEGs, expanding oxide interface spintronics beyond SrTiO3 systems.

Findings

Observation of DEE and IEE in KTaO3 2DEGs

Comparison of spin-charge conversion efficiency with SrTiO3 interfaces

Potential for spin-orbitronic device integration

Abstract

Oxide interfaces exhibit a broad range of physical effects stemming from broken inversion symmetry. In particular, they can display non-reciprocal phenomena when time reversal symmetry is also broken, e.g., by the application of a magnetic field. Examples include the direct and inverse Edelstein effects (DEE, IEE) that allow the interconversion between spin currents and charge currents. The DEE and IEE have been investigated in interfaces based on the perovskite SrTiO$_3$ (STO), albeit in separate studies focusing on one or the other. The demonstration of these effects remains mostly elusive in other oxide interface systems despite their blossoming in the last decade. Here, we report the observation of both the DEE and IEE in a new interfacial two-dimensional electron gas (2DEG) based on the perovskite oxide KTaO$_3$. We generate 2DEGs by the simple deposition of Al metal onto KTaO$_3$ single crystals, characterize them by angle-resolved photoemission spectroscopy and magnetotransport, and demonstrate the DEE through unidirectional magnetoresistance and the IEE by spin-pumping experiments. We compare the spin-charge interconversion efficiency with that of STO-based interfaces, relate it to the 2DEG electronic structure, and give perspectives for the implementation of KTaO$_3$ 2DEGs into spin-orbitronic devices.