Critical current scaling and anisotropy in oxypnictide superconductors

TL;DR

This study explores the anisotropic superconducting properties of LaFeAs(O,F) thin films, revealing multiband effects, temperature-dependent anisotropy, and pinning mechanisms, advancing understanding of oxypnictide superconductors.

Contribution

It demonstrates the applicability of Blatter scaling to multiband superconductors and characterizes the temperature dependence of anisotropy in LaFeAs(O,F).

Findings

Blatter scaling can be applied to multiband superconductors.

The mass anisotropy of LaFeAs(O,F) varies with temperature.

A steep increase in critical fields below 6K indicates a dirty limit in the smaller gap band.

Abstract

Investigating the anisotropy of superconductors permits an access to fundamental properties. Having succeeded in the fabrication of epitaxial superconducting LaFeAs(O,F) thin films we performed an extensive study of electrical transport properties. In face of multiband superconductivity we can demonstrate that a Blatter scaling of the angular dependent critical current densities can be adopted, although being originally developed for single band superconductors. In contrast to single band superconductors the mass anisotropy of LaFeAs(O,F) is temperature dependent. A very steep increase of the upper critical field and the irreversibility field can be observed at temperatures below 6K, indicating that the band with the smaller gap is in the dirty limit. This temperature dependence can be theoretically described by two dominating bands responsible for superconductivity. A pinning force scaling provides insight into the prevalent pinning mechanism and can be specified in terms of the Kramer model.