Superconductivity in Silver Induced by the Proximity Effect

The ratio of the thermal conductivities in the normal and superconducting states has been measured for silver made superconducting by the proximity effect. The results lead to measurements of the energy gap and, under certain conditions, of the electron-electron interaction, which is found to be attractive, with $NV=0.05\mathrm{}\pm 0.02$. A second independent determination is based on measurements of the supercooling field and, hence, the saturation temperature. It leads to $NV=0.08\mathrm{}$.