Dynamical spin polarization of excess quasi-particles in superconductors

TL;DR

This paper proposes that excess quasi-particles in superconductors can spontaneously form large, spin-polarized clusters, which could be detected through flux noise measurements, revealing new spin polarization phenomena.

Contribution

It introduces a novel mechanism for spontaneous spin polarization in superconductors via quasi-particle annihilation dynamics, with estimated large-scale spin clusters in aluminum.

Findings

Feasibility of forming spin clusters with total spin ~10^4 ħ in aluminum.

Large spin clusters could be spread over microns.

Flux noise measurements could detect the spin fluctuations.

Abstract

We show that the annihilation dynamics of excess quasi-particles in superconductors may result in the spontaneous formation of large spin-polarized clusters. This presents a novel scenario for spontaneous spin polarization. We estimate the relevant scales for aluminum, finding the feasibility of clusters with total spin $S \simeq 10^4 \hbar$ that could be spread over microns. The fluctuation dynamics of such large spins may be detected by measuring the flux noise in a loop hosting a cluster.