Specific heat of tantalum and tin near the superconducting critical temperature

Abstract

An unsuccessful search has been made for a λ-type of singularity in the specific heats of tantalum and tin. For these two metals an upper limit of 1-millijoule/mole/°K has been established for the entropy associated with such a singularity. In the analysis of the data it was found convenient to introduce a model for which it is supposed that a superconductor can be considered as an aggregate of many small, homogeneous volume elements. Each small-volume element is characterized by a critical temperature, T 0, and the temperatures T 0 are assumed to be distributed around a mean temperature T c. The fraction of the total volume of a specimen having critical temperature T 0 is taken to be N(T 0)=( 1 Δ π ) exp[ −(T e−T 0) 2 Δ 2 ] , where Δ is a measure of the temperature interval over which the transition takes place. For tin of high purity it appears that Δ is a linear function of resistance at 4.2°K, with dΔ dϱ = +3.6 °K/μohm cm .