Spin Hall effect generated by fluctuating vortices in type-II superconductors

TL;DR

This paper theoretically explores the vortex spin Hall effect in type-II superconductors, revealing how superconducting fluctuations significantly enhance the effect and suggesting new experimental directions.

Contribution

It introduces a microscopic theoretical framework for the vortex spin Hall effect driven by superconducting vortices, emphasizing the role of fluctuations and connecting to experimental observations.

Findings

Vortex spin Hall effect is strongly enhanced by superconducting fluctuations.

The effect shows a temperature-dependent voltage signal similar to vortex Nernst effect.

Proposes new experiments in fluctuation-dominant superconductors like cuprates.

Abstract

We theoretically investigate the vortex spin Hall effect, i.e., a novel spin Hall effect driven by the motion of superconducting vortices, by focusing on the role of superconducting fluctuations. Within the BCS-Gor'kov microscopic approach combined with the Kubo formula, we find a strong similarity between the vortex spin Hall effect and the vortex Nernst/Ettingshausen effect. Calculated temperature dependence of the voltage signal due to the inverse vortex spin Hall effect exhibits a strong enhancement by vortex fluctuations. This result not only provides a possible explanation for a prominent peak found in the spin Seebeck effect in a NbN/Y$_3$Fe$_5$O$_{12}$ system, but also leads to a proposal of new experiments using other superconductors with strong fluctuations, such as cuprate or iron-based superconductors.