A second superconducting energy gap of Nb_3Sn observed by breakjunction point-contact spectroscopy

TL;DR

This study provides the first spectroscopic evidence of a second energy gap in Nb_3Sn, confirming its classification as a two-band superconductor through breakjunction point-contact spectroscopy.

Contribution

It introduces the observation of a second superconducting energy gap in Nb_3Sn using breakjunction spectroscopy, expanding understanding of its electronic properties.

Findings

Identification of two distinct energy gaps in Nb_3Sn

First spectroscopic evidence of two-band superconductivity in Nb_3Sn

Results align with previous specific-heat measurements

Abstract

We report on investigations of the superconducting energy gap of the A15 superconductor Nb_3Sn by point-contact spectroscopy of breakjunctions. The voltage-dependent differential conductance dI/dV reveals features of a second energy gap besides the energy gap known from previous tunnel measurements with maxima at \Delta_1=3.92 +/- 0.16 meV and \Delta_2=0.85 +/- 0.17 meV as derived from a histogram summarizing the data of more than 60 contacts. These findings are the first spectroscopic evidence that Nb_3Sn belongs to the class of two-band superconductors and they are in line with low-temperature specific-heat measurements on Nb_3Sn.