A second superconducting energy gap of Nb3Sn observed by breakjunction point-contact spectroscopy
Abstract
We report on investigations of the superconducting energy gap of the A15 superconductor Nb3Sn 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 1=3.92 +/- 0.16 meV and 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 Nb3Sn belongs to the class of two-band superconductors and they are in line with low-temperature specific-heat measurements on Nb3Sn.
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