Ratio of superconducting transition temperatures in granular Nb films

Abstract
Experimental results on the resistive transition of superconducting granular Nb thin film bridges are reported which show a two part transition. The data are analyzed to extract a single grain transition temperature, Tco, and the long‐range phase‐ordering temperature Tc. The data are then compared to a recent theoretical model which predicts Tco/Tc=1+Rij/Ro where Rij is the average intergrain resistance, Ro∠zh//e2∠z⋅4500 Ω and z is the average number of nearest neighbor grains.