Local thermal fluctuations in current-carrying superconducting nanowires

TL;DR

This paper investigates how local thermal fluctuations in superconducting nanowires influence dark and photon count rates, revealing that fluctuations in electron energy cause observable effects in detection efficiency and spectral broadening.

Contribution

It introduces a model linking local thermal fluctuations to count rates and spectral features in current-carrying superconducting nanowires, providing new insights into fluctuation effects.

Findings

Dark counts are caused by thermal fluctuations in independent cells.

Photon count spectral broadening can be explained by local thermal fluctuations.

Fluctuations occur within cells of coherence length size.

Abstract

We analyze the effect of different types of fluctuations in internal electron energy on the rates of dark and photon counts in straight current-carrying superconducting nanowires. Dark counts appear due to thermal fluctuations in statistically independent cells with the effective size of the order of the coherence length; each count corresponds to an escape from the equilibrium state through an appropriate saddle point. For photon counts, spectral broadening of the deterministic cut off in the spectra of the detection efficiency can be phenomenologically explained by local thermal fluctuations in the electron energy within cells with the same effective volume as for dark counts.