Investigation of the electron-phonon interaction in $N{{b}_{3}}Sn$ with the aid of microcontacts

TL;DR

This study used microcontact spectroscopy to explore electron-phonon interactions in Nb3Sn superconductors, revealing variability in spectra linked to surface composition and demonstrating the technique's applicability in different contact types.

Contribution

It is the first to analyze electron-phonon interactions in Nb3Sn using microcontact spectroscopy in the superconducting state, including in both S-c-S and S-c-N contacts.

Findings

Spectra vary significantly between contacts due to surface composition differences.

Reproducible spectra in high-resistance contacts enable analysis of bulk electron-phonon interactions.

Microcontact spectroscopy is effective in superconducting Nb3Sn in various contact configurations.

Abstract

The method of microcontact spectroscopy in the superconducting state was used to investigate weak nonlinearities of the current-voltage characteristics of point contacts made of $N{{b}_{3}}Sn$ single crystals. The nature of the spectrum of the electron-phonon interaction was found to vary considerably from contact to contact, indicating considerable deviations of the composition of the surface of $N{{b}_{3}}Sn$ from stoichiometry. A correlation was established between the nature of the spectrum and the magnitude of the gap singularities of the current-voltage characteristics. In the case of "dirty" high-resistance contacts with strong gap singularities the microcontact spectra were reasonably reproducible, which made it possible to relate them sufficiently closely to the microcontact function of the electron-phonon interaction in the bulk material. It was found that microcontact spectroscopy of this interaction was possible in the superconducting state not only in dirty $S-c-S$ contacts, but also in dirty $S-c-N$ contacts.