Magnetic field attenuation by thin superconducting lead films

Abstract

Measurements have been made of the attenuation of an axial dc magnetic field by cylindrical thin films of superconducting lead. The normal-state resistance of each film was measured to determine the film thickness and the electron mean free path. The results have been used to derive the superconducting conductivity and the London-limit penetration depth ${\lambda }_L\mathrm{}\left(T\right)\mathrm{}$, and to infer the penetration depth $\lambda \mathrm{}\left(T\right)\mathrm{}$, which would be expected for pure bulk lead. Our experimental results for the temperature dependence of the superconducting conductivity and its value in the limit of zero temperature show unmistakable strong-coupling effects which agree well with our own theoretical calculations from previously obtained tunneling data and with published zero-temperature theoretical values. The analysis of the data indicates that ${\lambda }_L\mathrm{}\left(0\right)=315\mathrm{}\pm 7$ Å and the bulk zero-temperature penetration depth $\lambda \mathrm{}\left(0\right)\mathrm{}$ should be 453 ± 8 Å.