Reabsorption of nonequilibrium phonons at superconducting point contacts

TL;DR

This paper investigates how nonequilibrium phonons affect the current-voltage characteristics of superconducting point contacts, especially when the contact size exceeds the electron energy relaxation length, leading to structural features at phonon energies.

Contribution

It introduces a detailed analysis of phonon reabsorption effects in superconducting point contacts under nonequilibrium conditions, highlighting the impact on the energy gap and I-V characteristics.

Findings

Structural features appear at phonon energies in I-V curves.

Reabsorption of low-velocity phonons decreases the superconducting gap.

Effects are prominent when contact size exceeds energy relaxation length.

Abstract

When there is a deviation from the inequality $d\ll {{l}_{\varepsilon }}$ ($d$ is the contact diameter, and ${{l}_{\varepsilon }}$ is the energy relaxation length of the electrons), structural features are produced on the current-voltage characteristics of $S-c-N$ contacts at characteristic phonon energies because of the decrease in $\Delta $ due to the accumulation of nonequilibrium phonons with low group velocities near the contact.