Spin injection and relaxation in a mesoscopic superconductor

TL;DR

This study investigates how spin accumulation and relaxation behave in a superconducting nanowire, revealing significant enhancement of spin signals and identifying magnetic impurities as the main spin-flip mechanism.

Contribution

It provides experimental evidence of giant spin accumulation enhancement and distinguishes the dominant spin-flip mechanism in superconducting nanowires.

Findings

Spin accumulation increases by five orders of magnitude in the superconducting state.

Spin relaxation length decreases by an order of magnitude in the superconducting state.

Magnetic impurities dominate spin-flip scattering over spin-orbit coupling.

Abstract

We study spin accumulation and spin relaxation in a superconducting nanowire. Spins are injected and detected by using a set of magnetic tunnel contact electrodes, closely spaced along the nanowire. We observe a giant enhancement of the spin accumulation of up to five orders of magnitude on transition into the superconducting state, consistent with the expected changes in the density of states. The spin relaxation length decreases by an order of magnitude from its value in the normal state. These measurements combined with our theoretical model, allow us to distinguish the individual spin flip mechanisms present in the transport channel. Our conclusion is that magnetic impurities rather than spin-orbit coupling dominate spin-flip scattering in the superconducting state.