Abstract
By using effective-medium approaches, we obtain the onset of the electrical-resistivity rounding, above the normal-superconducting transition, associated with inhomogeneities of the mean-field critical temperature at scales larger than the superconducting correlation length. These results are compared with available data in single-crystal and single-phase (to within 4%) polycrystalline samples. This comparison shows that the measured resistivity rounding cannot be explained by these types of local inhomogeneities. Complementarily, our calculations allow us to check some proposals on inhomogeneities associated with local sample strains or oxygen-content variations. The interplay between inhomogeneities and superconducting order-parameter fluctuations (SCOPF) leads to the conclusion that in the mean-field-like region (MFR) above the superconducting transition, the inhomogeneity contribution to the measured resistivity rounding in high-quality (single-phase) cuprate oxide superconductors is negligible. In contrast, our analysis confirms that in the MFR these effects may be explained quantitatively on the grounds of the Lawrence-Doniach theory for SCOPF.
- Received 11 March 1991
DOI:https://doi.org/10.1103/PhysRevB.43.10560
©1991 American Physical Society