Experimental Determination of the Pair Susceptibility of a Superconductor

Abstract

An excess tunneling current due to order-parameter fluctuations has been found in tin---tin oxide---lead junctions just above the transition temperature of tin. Details of the variation of the excess current with voltage, magnetic field, and temperature are in agreement with a calculation by Scalapino in which the excess-current voltage characteristic is a direct measure of the frequency--- and wave-number---dependent pair susceptibility characteristic of the superconducting transition. Estimates of the pair relaxation frequency in tin based on the data are 50% greater than theoretical predictions.