Thickness Dependence of the I–V Characteristics in Indium Films

Abstract

Thickness dependence of the current-voltage (I–V)characteristics has been measured in quench-condensed films of indium with thickness 14 nm, 26 nm and 65 nm to study dissipation due to thermal fluctuations in the Meissner phase. The I–V curves for the 14 nm-thick film are qualitatively similar to the previous result for the much thinner film (5 nm) whose transport properties were well described by the two-dimensional (2D) Kosterlitz-Thouless (KT) theory. In contrast, those for the thicker films are markedly different. They obey the relation V/I ~ exp[-(I _T /I)] with a characteristic current scale I _T ~ 1/T for current less than the mean-field critical current. The result is consistent with the recent theoretical model for 3D superconductors which considers thermally activated nucleation and growth of vortex loops.