When there is a deviation from the inequality d≪lε (d is the contact diameter, and lε 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 Δ due to the accumulation of nonequilibrium phonons with low group velocities near the contact.
@article{arxiv.1602.04356,
title = {Reabsorption of nonequilibrium phonons at superconducting point contacts},
author = {I. K. Yanson and V. V. Fisun and N. L. Bobrov and L. F. Rybal'chenko},
journal= {arXiv preprint arXiv:1602.04356},
year = {2016}
}