Electron tunneling study of amorphous Pb-Bi superconducting alloys

Abstract

Electron tunneling studies carried out on amorphous Bi and Ga strong-coupling superconductors have been extended to a series of amorphous Pb-Bi superconducting alloys, ranging from 100% Pb to 100% Bi. The energy gap and transition temperature have been measured for each alloy composition, both in the amorphous state and after annealing to obtain the crystalline state. Phonon spectra have been derived for the amorphous state of the alloys by using the McMillan inversion program on our derivative tunneling data. Strong-coupling parameters derived from our phonon spectra have been used to test recent theories of the transition temperature of amorphous superconductors. The results are in reasonable agreement with the theories of Benda and of Garland et al.