Enhanced spin accumulation in a superconductor

TL;DR

This paper demonstrates a significant enhancement of spin accumulation in a superconductor, attributed to the superconducting gap reducing quasi-particle population, with measurements confirming increased spin diffusion length.

Contribution

It provides experimental evidence of enhanced spin accumulation in superconductors using ferromagnetic tunnel junctions, revealing the impact of the superconducting gap on spin transport.

Findings

Large increase in spin accumulation in the superconducting state

Superconducting gap reduces quasi-particle population

Spin diffusion length is determined in situ

Abstract

A lateral array of ferromagnetic tunnel junctions is used to inject and detect non-equilibrium quasi-particle spin distribution in a superconducting strip made of Al. The strip width and thickness is kept below the quasi particle spin diffusion length in Al. Non-local measurements in multiple parallel and antiparallel magnetic states of the detectors are used to in-situ determine the quasi-particle spin diffusion length. A very large increase in the spin accumulation in the superconducting state compared to that in the normal state is observed and is attributed to a diminishing of the quasi-particle population by opening of the gap below the transition temperature.