AC Response of Thin Film Superconductors at Various Temperatures and Magnetic Fields

TL;DR

This paper reviews the theory of ac susceptibilities in type-II superconductors, analyzing how they depend on temperature, magnetic fields, and material properties across different geometries.

Contribution

It provides a comprehensive theoretical framework for understanding linear and nonlinear ac susceptibilities in various geometries of thin film and bulk superconductors.

Findings

Susceptibility depends on complex resistivity and penetration depth.

Nonlinear susceptibility relates to electric field-current density dependence.

Material properties like pinning influence ac response.

Abstract

The basic theory of the linear and nonlinear ac susceptibilities of type-II superconductors is outlined for various geometries, e.g. circular and elliptic disks, rings, and strips of thin films or of thicker platelets in a perpendicular magnetic field. It is shown how the linear susceptibility depends on the linear complex resistivity or on the complex penetration depth, and the nonlinear susceptibility on the nonlinear dependence of the electric field on the current density and magnetic induction. The dependence of these constitutive laws on the temperature and on various material properties like pinning forces, pinning energies, structural defects, and granularity, leads to an implicit dependence of the ac susceptibility on these parameters.