Anomalous enhancement of spin Hall conductivity in superconductor/normal metal junction

TL;DR

This paper demonstrates that the spin Hall conductivity in a superconductor/normal metal junction can be significantly enhanced near the superconducting gap, offering a new method to control spin currents in spintronics.

Contribution

It introduces a novel spin Hall device exploiting resonant density of states enhancement to amplify spin Hall effects in SN junctions.

Findings

Spin Hall conductivity is anomalously enhanced near the superconducting gap.

Both side jump and skew scattering mechanisms contribute to the enhancement.

The enhancement allows for potential applications in spintronic devices.

Abstract

We propose a spin Hall device to induce a large spin Hall effect in a superconductor/normal metal (SN) junction. The side jump and skew scattering mechanisms are both taken into account to calculate the extrinsic spin Hall conductivity in the normal metal. We find that both contributions are anomalously enhanced when the voltage between the superconductor and the normal metal approaches to the superconducting gap. This enhancement is attributed to the resonant increase of the density of states in the normal metal at the Fermi level. Our results demonstrate a novel way to control and amplify the spin Hall conductivity by applying an external dc electric field, suggesting that a SN junction has a potential application for a spintronic device with a large spin Hall effect.