Effective medium theory for superconducting layers: A systematic analysis including space correlation effects

TL;DR

This paper analyzes how mesoscopic inhomogeneities and space correlations influence the metal-superconductor transition in two-dimensional systems, highlighting the dominant role of disorder and explaining resistivity tail features.

Contribution

It introduces a systematic analysis combining numerical and effective medium approaches to study inhomogeneity effects on superconducting transitions.

Findings

Disorder primarily determines transition width.

Bimodal Tc distribution causes resistivity tails.

Space correlations influence local superconducting properties.

Abstract

We investigate the effects of mesoscopic inhomogeneities on the metal-superconductor transition occurring in several two-dimensional electron systems. Specifically, as a model of systems with mesoscopic inhomogeneities, we consider a random-resistor network, which we solve both with an exact numerical approach and by the effective medium theory. We find that the width of the transition in these two-dimensional superconductors is mainly ruled by disorder rather than by fluctuations. We also find that "tail" features in resistivity curves of interfaces between LaAlO3 or LaTiO3 and SrTiO3 can arise from a bimodal distribution of mesoscopic local Tc's and/or substantial space correlations between the mesoscopic domains.