Specific heat of composite superconductors in the proximity-effect regime

Abstract

The specific heat of a series of Pb-Cd laminar composites with layer spacings ranging from 1000 to 85 000 Å has been measured in order to study the superconducting proximity effect in bulk material. The jump in specific heat at the transition temperature is very sensitive to the spatial dependence of the superconducting order parameter and these measurements provide an estimate of this spatial distribution. Results show that the fourth moment of the order parameter is approximately 10% larger than the square of the second moment. The presence of the interleaved nonmagnetic normal-metal layers is not very detrimental to the superconductivity.