Supercurrent fluctuations in short filaments

TL;DR

This paper analyzes supercurrent fluctuations in superconducting nanobridges, revealing their dependence on temperature and phase difference, and highlighting differences from normal current fluctuations with potential for experimental measurement.

Contribution

It provides a detailed evaluation of supercurrent fluctuations' statistical properties in short superconducting filaments, a topic not extensively explored before.

Findings

Supercurrent fluctuations depend on phase difference and temperature.

Standard deviation of fluctuations can be time-independent.

Results are consistent across different filament types.

Abstract

We evaluate the average and the standard deviation of the supercurrent in superconducting nanobridges, as functions of the temperature and the phase difference, in an equilibrium situation. We also evaluate the autocorrelation of the supercurrent as a function of the elapsed time. The behavior of supercurrent fluctuations is qualitatively different from from that of the normal current: they depend on the phase difference, have a different temperature dependence, and for appropriate range their standard deviation is independent of the probing time. We considered two radically different filaments and obtained very similar results for both. Fluctuations of the supercurrent can in principle be measured.