Meissner response of superconductors with inhomogeneous penetration depths

TL;DR

This paper analyzes how inhomogeneities in penetration depth affect the Meissner response in superconductors, providing simplified models for planar defects relevant to magnetic microscopy techniques.

Contribution

It introduces simplified expressions for the Meissner response in superconductors with inhomogeneous penetration depths, focusing on planar defects for experimental comparison.

Findings

Derived expressions for inhomogeneous penetration depths in various geometries.

Focused analysis on planar defects perpendicular to the surface.

Results applicable to magnetic microscopy imaging techniques.

Abstract

We discuss the Meissner response to a known field source of superconductors having inhomogeneities in their penetration depth. We simplify the general problem by assuming that the perturbations of the fields by the penetration depth inhomogeneities are small. We present expressions for inhomogeneities in several geometries, but concentrate for comparison with experiment on planar defects, perpendicular to the sample surfaces, with superfluid densities different from the rest of the samples. These calculations are relevant for magnetic microscopies, such as Scanning Superconducting Quantum Interference Device (SQUID) and Magnetic Force Microscope, which image the local diamagnetic susceptibility of a sample.