Two-band effect on the vortex dynamics and critical current density in an anisotropic MgB$_2$ thin film

TL;DR

This study investigates how intrinsic superconducting parameters influence vortex behavior and critical current density in an MgB₂ thin film, highlighting the effects of two-band superconductivity on vortex pinning and critical current suppression.

Contribution

It provides new insights into the two-band effects on vortex dynamics and critical current density in MgB₂ thin films, linking intrinsic parameters to observed behaviors.

Findings

High critical current density at low fields

Suppression of superconductivity in the and under magnetic field

High pinning energies at low field that decrease with increasing field

Abstract

We report the influence of intrinsic superconducting parameters on the vortex dynamics and the critical current densities of a MgB$_2$ thin film. The small magnetic penetration depth of \lambda = 50 nm at T=4 K is related to a clean \pi-band, and transport and magnetization data show an upper critical field similar to those reported in clean single crystals. We find a high self-field critical current density Jc, which is strongly reduced with applied magnetic field, and attribute this to suppression of the superconductivity in the \pi-band. The temperature dependence of the creep rate S(T) at low magnetic field can be explained by a simple Anderson-Kim mechanism. The system shows high pinning energies at low field that are strongly suppressed by high field, which is consistent with a two-band contribution.