Conductivity of anisotropic inhomogeneous superconductors above critical temperature

TL;DR

This paper develops an analytical model for conductivity in anisotropic, inhomogeneous superconductors with isolated superconducting islands, explaining experimental resistivity data above the critical temperature in various materials.

Contribution

It introduces a new analytical model for conductivity in anisotropic inhomogeneous superconductors with ellipsoid inclusions, aiding the analysis of temperature-dependent anisotropy.

Findings

Model explains resistivity above Tc in high-Tc superconductor YBa2Cu4O8

Model explains resistivity above Tc in organic superconductor β-(BEDT-TTF)2I3

Estimated superconducting inclusion size as approximately 1 micron

Abstract

We propose a model and derive analytical expressions for conductivity in heterogeneous fully anisotropic conductors with ellipsoid superconducting inclusions. This model and calculations are useful to analyze the observed temperature dependence of conductivity anisotropy in various anisotropic superconductors, where superconductivity onset happens inhomogeneously in the form of isolated superconducting islands. The results are applied to explain the experimental data on resistivity above the transition temperature $T_c$ in the high-temperature superconductor $\mathrm{YBa_2Cu_4O_8}$ and in the organic superconductor $\beta$-(BEDT-TTF)$_{2}$I$_{3}$. The comparison of resistivity data and diamagnetic response in $\beta$-(BEDT-TTF)$_{2}$I$_{3}$ allows us to estimate the size of superconducting inclusions as $d\sim 1\mu m$.