Effects of critical temperature inhomogeneities on the voltage-current characteristics of a planar superconductor near the Berezinskii-Kosterlitz-Thouless transition

We analyze numerically how the voltage-current (V-I) characteristics near the so-called Berezinskii-Kosterlitz-Thouless (BKT) transition of 2D superconductors are affected by a random spatial Gaussian distribution of critical temperature inhomogeneities with long characteristic lengths (much larger than the in-plane superconducting coherence length amplitude). Our simulations allow to quantify the broadening around the average BKT transition temperature of both the exponent alpha in V I^alpha and of the resistance V/I. These calculations reveal that strong spatial redistributions of the local current will occur around the transition as either I or the temperature T are varied. Our results also support that the condition alpha=3 provides a good estimate for the location of the average BKT transition temperature, and that extrapolating to alpha->1 the alpha(T) behaviour well below the transition provides a good estimate for the average mean-field critical temperature.Comment: 18 pages; pdfLaTeX; 1 TeX file + 8 PDF files for figures (figs.1,2,3a,3b,4,5a,5b,6