Signatures of Gaussian superconducting fluctuations in nonlocal noise magnetometry

TL;DR

This paper calculates the magnetic noise spectrum caused by Gaussian superconducting fluctuations, measurable via spin qubits, using Ginzburg-Landau theory, with implications for high-temperature superconductors.

Contribution

It provides a theoretical framework for detecting superconducting fluctuations through magnetic noise measurements using spin qubits.

Findings

Magnetic noise spectrum is directly linked to fluctuating Cooper pairs.

The analysis applies to both 2D systems and wires in equilibrium and under electric fields.

Contrasts fluctuations signatures with vortex liquid predictions.

Abstract

We calculate the two-point magnetic noise spectrum arising from Gaussian superconducting fluctuations, a quantity directly measurable by spin qubit pairs such as nitrogen vacancy centers in diamond. The analysis utilizes the time-dependent Ginzburg-Landau theory, reflecting the direct contribution of fluctuating Cooper pairs to the current correlations and consequent magnetic noise. We treat both two-dimensional systems and wires, considering them in equilibrium and under a uniform electric field. The signal is expected to be strongest in high-temperature superconductors, and we contrast our findings with the predicted signatures of a vortex liquid to offer an additional route to elucidate the nature of fluctuations in these systems.