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

TL;DR

This study numerically investigates how spatial inhomogeneities in critical temperature affect the voltage-current characteristics of 2D superconductors near the BKT transition, revealing broadening effects and estimation methods for transition temperatures.

Contribution

It introduces a numerical analysis of inhomogeneity effects on BKT transition characteristics, providing new insights into transition broadening and temperature estimation methods.

Findings

Spatial inhomogeneities cause broadening of the BKT transition features.

The alpha=3 criterion estimates the average BKT transition temperature.

Extrapolating alpha(T) to 1 below the transition estimates the mean-field critical temperature.

Abstract

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.