Quantification of interfacial spin-charge conversion in metal/insulator hybrid structures by generalized boundary conditions

TL;DR

This paper develops and experimentally verifies a universal theoretical framework for understanding spin-charge conversion at metal/insulator interfaces with spin-orbit coupling, linking interfacial parameters to device performance.

Contribution

The authors introduce a generalized boundary condition approach that accurately describes spin-charge interconversion in metal/insulator structures with ISOC, validated by experiments.

Findings

Conversion efficiency depends solely on interfacial parameters

The formalism accurately predicts device behaviors

Experimental measurements confirm theoretical predictions

Abstract

We present and verify experimentally a universal theoretical framework for the description of spin-charge interconversion in non-magnetic metal/insulator structures with interfacial spin-orbit coupling (ISOC). Our formulation is based on drift-diffusion equations supplemented with generalized boundary conditions. The latter encode the effects of ISOC and relate the electronic transport in such systems to spin loss and spin-charge interconversion at the interface, which are parameterized, respectively, by $G_{\parallel/\perp}$ and $\sigma_{\rm{sc/cs}}$. We demonstrate that the conversion efficiency depends solely on these interfacial parameters. We apply our formalism to two typical spintronic devices that exploit ISOC: a lateral spin valve and a multilayer Hall bar, for which we calculate the non-local resistance and the spin Hall magnetoresistance, respectively. Finally, we perform measurements on these two devices with a BiO$_x$/Cu interface and verify that transport properties related to the ISOC are quantified by the same set of interfacial parameters.