Vortex Interaction with Mesoscopic Irregularities in High Temperature Superconductors

TL;DR

This paper investigates how vortex lines in high temperature superconductors interact with surface irregularities of mesoscopic scale, revealing conditions under which surface barriers vanish or persist, supported by theoretical and experimental comparisons.

Contribution

It introduces a conformal mapping approach to analyze vortex interactions with surface cavities at mesoscopic scales, highlighting the impact of irregularity size on surface barrier behavior.

Findings

Surface barriers can vanish at weak points with mesoscopic irregularities.

Surface barrier disappears when defect size exceeds penetration length.

Metastable states occur when irregularity size is within coherence length.

Abstract

The conformal mapping method is used to study the problem of flux line interaction with surface cavities having cylindrical profile and characteristic size much less than the penetration length, i.e, within mesoscopic scale. It is shown that the metastable states are achieved when the dimensions of the surface irregularities do not exceed the coherence length. Our study shows that the surface barrier may vanished at some weak point at which the surface irregularities have mesoscopic scales. On the other hand, the surface barrier is completely disappeared when the surface defects size is more greater than penetration length. Our results are compared with the available experimental data and theoretical results.