Proximity electron tunnelling spectroscopy of Ta: inapplicability of an 'empirical model'

BCS theory has to be overhauled: Reassurance from numerical survival rate

“…Khim measured an Al/Pb proximate junction in 1979 and extracted α 2 F (ν) (grey silhouette in FIG. 4) but did not publish the tunnelling data [39,40]. From the Khim α 2 F (ν) data we find the superconducting energy gap function via the BCS-Eliashberg-Nambu equation which in turn leads via the formula in for example [19] to the aluminium tunnelling conductance we need as experimental input.…”

Extracting a More Realistic Pseudopotential for Aluminum, Lead, Niobium and Tantalum from Superconductor Electron Tunnelling Spectroscopy Data

“…In 1970 Shen [33] measured the tunnelling current from tantalum and inverted the data to find the experimental α 2 F (ν). In 1981 Wolf et al [34] performed proximity electron tunnelling measurement on tantalum, yielding experimental α 2 F (ν) consistent with that in [33]. In 1987 Al-Lehaibi, Swihart, Butler and Pinski [8] calculated theoretical α 2 F (ν) for tantalum, based on Korringa-Kohn-Rostoker energy bands, Bornvon Kármán phonons and the rigid muffin tin model for the electron-phonon matrix element.…”

Discrepancy between theory and measurement of superconducting vanadium

“…and first principles calculation (circles). Lower: electron-phonon spectral density from formal inversion [34] (silhouette) and first principles calculation (histogram).…”

“…7 we use the solid line to show the experimentally measured tunnelling conductance data for tantalum by Wolf et al [34]. It leads to the experimental a 2 FðmÞ shown as the grey silhouette in the lower part of the figure via formal inversion through the procedure of McMillan and Rowell [35].…”