The ratio of energy gap to transition temperature in amorphous superconductors

Using results of tunneling measurements, values of 2Δ(o)/kTc for a number of amorphous transition-metal based superconductors are found to be 3.5±0.1 in agreement with the BCS theory in the weak-coupled limit unlike previously reported results suggesting strong electron-phonon coupling in amorphous non-transition metals such as Ga and Pb-Bi alloys. A comparison of our results with existing data for amorphous soft-metal alloys and A-15 compounds suggests that non-crystallinity alone does not give rise to a significantly enhanced electron-phonon interaction. © 1977.