Nonlocal Spin Transport Mediated by a Vortex Liquid in Superconductors

TL;DR

This paper introduces a novel approach to spin transport using mobile vortices in superconductors, demonstrating algebraic decay of signals and proposing a universal framework for topological excitation hydrodynamics.

Contribution

It develops a phenomenological theory for spin-vorticity interconversion at superconductor-magnet interfaces and shows vortices can mediate long-range spin transport.

Findings

Vortex liquid enables nonlocal spin transport between magnetic insulators.

Spin signals decay algebraically with distance, unlike quasiparticle transport.

Hydrodynamics of topological excitations may provide a universal transport framework.

Abstract

Departing from the conventional view on superconducting vortices as a parasitic source of dissipation for charge transport, we propose to use mobile vortices as topologically-stable information carriers for spin transport. To this end, we start by constructing a phenomenological theory for the interconversion between spin and vorticity, a topological charge carried by vortices, at the interface between a magnetic insulator and a superconductor, by invoking the interfacial spin Hall effect therein. We then show that a vortex liquid in superconductors can serve as a spin-transport channel between two magnetic insulators by encoding spin information in the vorticity. The vortex-mediated nonlocal signal between the two magnetic insulators is shown to decay algebraically as a function of their separation, contrasting with the exponential decay of the quasiparticle-mediated spin transport. We envision that hydrodynamics of topological excitations, such as vortices in superconductors and domain walls in magnets, may serve as a universal framework to discuss long-range transport properties of ordered materials.