Magnetic Properties of the transition to localized superconductivity around columnar defects

TL;DR

This paper investigates the transition from flux line to localized superconductivity around columnar defects, revealing a new vortex state characterized by unique supercurrent flows and introducing methods to analyze vorticity and magnetization in complex geometries.

Contribution

It introduces a new vortex state due to supercurrent flows around defects and proposes a general operator for vorticity and a method for magnetization analysis in superconductors.

Findings

Identification of a new vortex state with circulating supercurrents.

Development of a general vorticity counting operator.

A novel method for calculating magnetization in multiply connected superconductors.

Abstract

We consider flux lines in presence of a dense square array of columnar defects, with insulating core and radius of the order of the coherence length. The properties of the phase transition from the flux line regime to the localized superconducting state are determined here. We show that the localized superconducting state is a new vortex state because of the counterclockwise and of the clockwise supercurrent flows found around each defect. We propose here a general operator to count the vorticity of any cavity inside a superconductor and give a new method to obtain the reversible magnetization of superconductors with multiply connected geometries.