Intrinsic Quasiparticle Lifetime in a Superconducting Aluminum

TL;DR

This study measures quasiparticle lifetimes in superconducting aluminum across a temperature range, revealing deviations from theory at low temperatures and indicating rapid quasiparticle-quasiparticle relaxation.

Contribution

It provides experimental data on quasiparticle decay in superconducting Al and compares it with theoretical models, highlighting discrepancies at low temperatures.

Findings

Quasiparticle lifetime matches electron-phonon energy flow at high T

At low T, lifetime is shorter than predicted by theory

Quasiparticle-quasiparticle relaxation is faster than electron-phonon interaction

Abstract

We use time-resolved thermometry to monitor the decay of nonequilibrium quasiparticles in superconducting Al in the temperature range from $0.3\,$K to $1.2\,$K. The quasiparticle lifetime at higher temperatures ($T>0.7\,$K) agrees well with the calculated energy flow from electrons to phonons, but at lower temperatures it is significantly shorter than the theory predicts. We show well-defined internal equilibrium of quasiparticle system in the studied thermal transients, which implicates that quasiparticle-quasiparticle relaxation is much faster than electron-phonon interaction.