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Highly efficient and tunable spin-to-charge conversion through Rashba coupling at oxide interfaces

Abstract

The spin–orbit interaction couples the electrons’ motion to their spin. As a result, a charge current running through a material with strong spin–orbit coupling generates a transverse spin current (spin Hall effect, SHE) and vice versa (inverse spin Hall effect, ISHE). The emergence of SHE and ISHE as charge-to-spin interconversion mechanisms offers a variety of novel spintronic functionalities and devices, some of which do not require any ferromagnetic material. However, the interconversion efficiency of SHE and ISHE (spin Hall angle) is a bulk property that rarely exceeds ten percent, and does not take advantage of interfacial and low-dimensional effects otherwise ubiquitous in spintronic hetero- and mesostructures. Here, we make use of an interface-driven spin–orbit coupling mechanism—the Rashba effect—in the oxide two-dimensional electron system (2DES) LaAlO3/SrTiO3 to achieve spin-to-charge conversion with unprecedented efficiency. Through spin pumping, we inject a spin current from a NiFe film into the oxide 2DES and detect the resulting charge current, which can be strongly modulated by a gate voltage. We discuss the amplitude of the effect and its gate dependence on the basis of the electronic structure of the 2DES and highlight the importance of a long scattering time to achieve efficient spin-to-charge interconversion.

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Figure 1: Characterization of NiFe/LAO//STO system.
Figure 2: Ferromagnetic resonance in NiFe/LAO//STO.
Figure 3: Spin-to-charge conversion in LAO//STO 2DES.
Figure 4: Gate control of the inverse Edelstein effect in LAO//STO 2DES.

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Acknowledgements

Research at CNRS/Thales received support from the ERC Consolidator Grant #615759 “MINT” and the region Île-de-France DIM “Oxymore” (project NEIMO). Support from the ANR SOspin and ANR Lacunes projects is also acknowledged. H.N. was partly supported by the Leading Young Researcher Overseas Visit Program, JSPS Grant-in-Aid for Scientific Research (B) (#15H03548). Authors are grateful to Y. Kodama (Tohoku University, Japan) for TEM observation and to N. Reyren for his help at the early stage of the project.

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Contributions

M.B., L.V., E.L., J.C.R.-S., H.J. and J.-M.G. conceived and designed the experiment. M.B. and L.V. supervised the project. E.L. and D.C.V. grew the samples with the help of H.N. and E.J., and performed the d.c. transport experiments and analysed the data. E.L., J.C.R.-S., Y.F., S.O. and J.-M.G. performed the room-temperature FMR measurements and analysed the data. Y.F., S.O., J.C.R.-S., E.L. and L.V. performed the low-temperature spin-pumping experiments and analysed the data with the help of M.B., H.J. and A.F. M.B. and E.L. wrote the manuscript, with inputs from H.J. All authors discussed the data and contributed to the manuscript.

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Correspondence to J. C. Rojas-Sánchez or M. Bibes.

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Lesne, E., Fu, Y., Oyarzun, S. et al. Highly efficient and tunable spin-to-charge conversion through Rashba coupling at oxide interfaces. Nature Mater 15, 1261–1266 (2016). https://doi.org/10.1038/nmat4726

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