Hotspot Relaxation Dynamics in a Current Carrying Superconductor

TL;DR

This study investigates how optically excited hotspots in WSi superconducting nanowires relax under various conditions, revealing slower relaxation compared to NbN and dependencies on bias current, temperature, and wavelength, explained by a quasiparticle recombination model.

Contribution

The paper provides the first detailed experimental analysis of hotspot relaxation dynamics in WSi nanowires, highlighting their differences from NbN and introducing a model based on quasiparticle recombination.

Findings

Hotspot relaxation is ~4 times slower in WSi than NbN.

Hotspot relaxation time depends on bias current.

The current dependence varies with temperature and wavelength.

Abstract

We experimentally studied the dynamics of optically excited hotspots in current carrying WSi superconducting nanowires as a function of bias current, bath temperature and excitation wavelength. We discovered that: (1) the hotspot relaxation is a factor of ~ 4 slower in WSi than in NbN; (2) the hotspot relaxation time depends on bias current, and (3) the current dependence of the hotspot relaxation time changes with temperature and wavelength. We explained all of these effects with a model based on quasi particle recombination.