Energy-dependent kinetic model of photon absorption by superconducting tunnel junctions

TL;DR

This paper introduces an energy-dependent kinetic model for photon absorption in superconducting tunnel junctions, improving upon previous models by accurately capturing quasiparticle dynamics for advanced detector applications.

Contribution

The model incorporates full energy dependence of quasiparticle processes, surpassing the Rothwarf-Taylor approach for small gap structures in superconducting detectors.

Findings

The model accurately predicts quasiparticle energy distributions over time.

Good agreement between theoretical predictions and experimental data.

Enhanced understanding of quasiparticle relaxation in superconducting detectors.

Abstract

We describe a model for photon absorption by superconducting tunnel junctions in which the full energy dependence of all the quasiparticle dynamic processes is included. The model supersedes the well-known Rothwarf-Taylor approach, which becomes inadequate for a description of the small gap structures that are currently being developed for improved detector resolution and responsivity. In these junctions relaxation of excited quasiparticles is intrinsically slow so that the energy distribution remains very broad throughout the whole detection process. By solving the energy-dependent kinetic equations describing the distributions, we are able to model the temporal and spectral evolution of the distribution of quasiparticles initially generated in the photo-absorption process. Good agreement is obtained between the theory and experiment.