Modelling reduced field dependence of $j_c$ in YBCO films with nanorods

TL;DR

This paper models how columnar defects influence the critical current in YBCO superconducting films, explaining the characteristic field dependence and the effects of defect size on vortex lattice order.

Contribution

It introduces a Ginzburg-Landau based model that accounts for defect size and predicts the critical current behavior in doped YBCO films with aligned nanorods.

Findings

Critical current shape is reproduced and explained by the model.

Defect size significantly affects vortex lattice order.

Model highlights the importance of defect size in flux pinning efficiency.

Abstract

Flux pinning is still the main limiting factor for the critical current of the high-temperature superconductors in high fields. In this paper we model the field dependence of the critical current in thin films with columnar defects aligned with the field. The characteristic shape of the critical current of the BaZrO$_3$ doped YBa$_2$Cu$_3$O$_{6+x}$ thin films is reproduced and explained. The model is based on solving the Ginzburg-Landau equations with columnar defects present in the lattice. The size of the columnar defect is found to be of key importance in explaining the rounded shape of the critical current of the BaZrO$_3$ doped YBa$_2$Cu$_3$O$_{6+x}$ thin films. It is also found that the size of the rod changes the long range order of the vortex lattice.