Nonequilibrium Superconductor-Normal Metal Tunnel Contact and the Phonon Deficit Effect

TL;DR

This paper explores the theoretical connection between experimental superconductor-normal metal tunnel refrigerators and the phonon deficit effect, emphasizing the importance of including phonons microscopically in the analysis.

Contribution

It provides the first theoretical framework linking experimental SN tunnel refrigerator results with the phonon deficit effect by incorporating phonons microscopically.

Findings

The phonon deficit effect can be a key mechanism in superconductor-normal metal microrefrigerators.

A theoretical model including phonons explains experimental observations.

The study suggests new directions for designing superconducting microrefrigerators.

Abstract

We consider tunnel microrefrigerators at low temperature. There is a number of experimental studies performed on microrefrigeration in tunneling superconductor--normal metal (SN) structures. Related to these experiments, only the electron subsystem has been considered theoretically. Independently, the phonon deficit effect has been studied a while ago in superconductor-superconductor tunnel junctions. It can be regarded as a possible prototype scheme for superconducting microrefrigerators. We try to provide the missing link between experiments on the SN tunnel junction refrigerators and the theory which includes microscopically phonons in combination with the mechanism of the phonon deficit effect.