The Crossover beteween Aslamazov-Larkin and Short Wavelength Fluctuations Regimes in HTS Conductivity Experiments

TL;DR

This study investigates the crossover between Aslamazov-Larkin and short wavelength fluctuation regimes in high-temperature superconductor conductivity, revealing universal behavior beyond the Lawrence-Doniach crossover point.

Contribution

It provides experimental evidence of the universal fluctuation conductivity behavior in HTS across different compounds and clarifies the role of anisotropy and fluctuation regimes.

Findings

Lawrence-Doniach crossover shifts with anisotropy.

Universal $1/$ law observed for $ > 0.23$.

Short wavelength fluctuations dominate at high temperatures.

Abstract

We present paraconductivity (AL) measurements in three different high temperature superconductors: a melt textured $YBa_2Cu_3O_7$ sample, a $Bi_2Sr_2CaCu_2O_8$ epitaxial thin film and a highly textured $Bi_2Sr_2Ca_2Cu_3O_{10}$ tape. The crossovers between different temperature regimes in excess conductivity have been analysed. The Lawrence-Doniach (LD) crossover, which separates the 2D and 3D regimes, shifts from lower to higher temperatures as the compound anisotropy decreases. Once the LD crossover is overcome, the fluctuation conductivity of the three compounds shows the same universal behaviour: for $\epsilon =\ln T/T_c > 0.23$ all the curves bend down according to the $1/\epsilon^3$ law. This asymptotic behaviour was theoretically predicted previously for the high temperature region where the short wavelength fluctuations (SWF) become important.