Point-contact spectroscopy of electron-phonon interaction in superconductors

TL;DR

This paper demonstrates how point-contact spectroscopy can reconstruct the electron-phonon interaction function in superconductors by analyzing the superconducting inelastic contribution to excess current, considering both weak and strong EPI cases.

Contribution

It introduces a method to reconstruct the EPI function in superconductors using point-contact spectroscopy, accounting for elastic components in strong EPI cases.

Findings

Reconstruction of EPI function is possible in S-c-N and S-c-S contacts.

Superconductors with strong EPI require accounting for elastic current components.

Frequency dependence of the superconducting gap affects EPI analysis.

Abstract

The possibility to reconstruct the electron-phonon interaction (EPI) function was demonstrated for S-c-N and S-c-S point contacts using the superconducting inelastic contribution to the excess current caused by Andreev reflection processes. Superconductors with both weak (Sn, Al) and strong (Pb, In) EPI were considered. It was shown that in the latter case it is necessary to account for the elastic component of current which is related to the frequency dependence of the superconducting energy gap arising due to electron-phonon renormalization of the energy spectrum of the superconductor.