Resistive state of superconducting structures with fractal clusters of a normal phase

TL;DR

This paper investigates how fractal normal phase clusters in superconductors influence magnetic flux pinning, critical currents, and resistive behavior, revealing that fractality enhances flux trapping and current capacity.

Contribution

It introduces a statistical model of fractal cluster areas, derives the critical current distribution, and analyzes how fractal boundaries affect superconducting properties.

Findings

Fractal clusters increase magnetic flux trapping.

Fractality enhances the superconductor's current-carrying capacity.

Voltage-current characteristics depend on fractal dimension.

Abstract

The effect of morphologic factors on magnetic flux dynamics and critical currents in percolative superconducting structures is considered. The superconductor contains the fractal clusters of a normal phase, which act as pinning centers. The properties of these clusters are analyzed in the general case of gamma-distribution of their areas. The statistical characteristics of the normal phase clusters are studied, the critical current distribution is derived, and the dependencies of the main statistical parameters on the fractal dimension are found. The effect of fractal clusters of a normal phase on the electric field induced by the motion of the magnetic flux after the vortices have been broken away from pinning centers is considered. The voltage-current characteristics of fractal superconducting structures in a resistive state for an arbitrary fractal dimension are obtained. It is found that the fractality of the boundaries of normal phase clusters intensifies magnetic flux trapping and thereby increases the current-carrying capability of the superconductor.