Meissner response of anisotropic superconductors

TL;DR

This paper analyzes the magnetic response of anisotropic superconductors to weak external fields, providing detailed models for different sources and conditions, and discusses limitations in measuring penetration depth accurately.

Contribution

It presents a comprehensive evaluation of the Meissner response in anisotropic superconductors for arbitrary weak external sources, including point and circular current sources, and extends the analysis to thin films.

Findings

Major contribution from source image field when penetration depth is small

Absolute value of penetration depth cannot be precisely determined from response

Response behavior characterized for both bulk and thin film geometries

Abstract

The response field of a half-space anisotropic superconductor is evaluated for an arbitrary weak external field source. Example sources of a point magnetic moment and a circular current are considered in detail. For the penetration depth $\lambda \ll L$ with $L$ being any other relevant distance (the source size, or the distance between the source and the superconductor), the major contribution to the response is the $\lambda$ independent field of the source image. It is shown that the absolute value of $\lambda$ cannot be extracted from the response field with a better accuracy than that for the source position. Similar problems are considered for thin films.