Detecting vortex motion through spatially correlated nonequilibrium noise

TL;DR

This paper introduces a novel method using covariance magnetometry with nitrogen-vacancy centers to distinguish vortex motion from quasiparticle transport in superconductors by detecting directional magnetic noise correlations.

Contribution

It proposes an unambiguous, experimentally feasible technique to identify vortex-driven transport through spatially correlated magnetic noise analysis.

Findings

The method can differentiate vortex motion from quasiparticle transport based on noise anisotropy.

Simulations show the expected noise signals are detectable with current technology.

The approach provides a new tool for studying superconducting vortex dynamics.

Abstract

Resistive transport near a superconducting phase can arise from the motion of normal-state quasiparticles or that of vortices. The conductivity alone does not distinguish between these mechanisms. We propose an unambiguous method for telling them apart, using the recently developed experimental tool of covariance magnetometry, which uses nitrogen-vacancy centers in diamond to probe real-time spatiotemporal correlations in magnetic noise. Our key insight is that, under an applied current, the underlying charge carriers leave a directional fingerprint in the spatially correlated magnetic noise above the sample: ordinary electric carriers drift parallel to the current, whereas vortices, owing to the Magnus force, drift perpendicular to it. The noise covariance detects this anisotropy and identifies the vortex-driven nature of transport. We compute the noise correlations expected for a representative thin-film superconductor and demonstrate that the anisotropic signal is well within the reach of current experimental capabilities.