Spin Transport at Interfaces with Spin-Orbit Coupling: Phenomenology

TL;DR

This paper develops boundary conditions for drift-diffusion models to effectively describe spin transport at interfaces with spin-orbit coupling, simplifying analysis and capturing the influence of in-plane electric fields on spin current generation.

Contribution

It introduces boundary conditions for drift-diffusion models that accurately incorporate interfacial spin-orbit effects, aligning with Boltzmann equation solutions and enhancing interpretability.

Findings

Boundary conditions match Boltzmann equation solutions.

In-plane electric fields influence spin current generation.

Interfacial spin currents impact spin torque mechanisms.

Abstract

This paper presents the boundary conditions needed for drift-diffusion models to treat interfaces with spin-orbit coupling. Using these boundary conditions for heavy metal/ferromagnet bilayers, solutions of the drift-diffusion equations agree with solutions of the spin-dependent Boltzmann equation and allow for a much simpler interpretation of the results. A key feature of these boundary conditions is their ability to capture the role that in-plane electric fields have on the generation of spin currents that flow perpendicularly to the interface. The generation of these spin currents is a direct consequence of the effect of interfacial spin-orbit coupling on interfacial scattering. In heavy metal/ferromagnet bilayers, these spin currents provide an important mechanism for the creation of damping-like and field-like torques; they also lead to possible reinterpretations of experiments in which interfacial contributions to spin torques are thought to be suppressed.