"Unusual" critical states in type-II superconductors

TL;DR

This paper provides a theoretical framework for understanding complex critical states in type-II superconductors where currents are not perpendicular to magnetic induction, expanding beyond traditional models.

Contribution

It introduces a general description of critical states without flux-line cutting, applicable to asymmetric geometries and complex magnetic field configurations.

Findings

Critical states differ significantly from Bean states in certain geometries.

Analysis of slab and strip geometries under complex magnetic field applications.

Theoretical predictions of non-perpendicular critical current configurations.

Abstract

We give a theoretical description of the general critical states in which the critical currents in type-II superconductors are not perpendicular to the local magnetic induction. Such states frequently occur in real situations, e.g., when the sample shape is not sufficiently symmetric or the direction of the external magnetic field changes in some complex way. Our study is restricted to the states in which flux-line cutting does not occur. The properties of such general critical states can essentially differ from the well-known properties of the usual Bean critical states. To illustrate our approach, we analyze several examples. In particular, we consider the critical states in a slab placed in a uniform perpendicular magnetic field and to which two components of the in-plane magnetic field are then applied successively. We also analyze the critical states in a long thin strip placed in a perpendicular magnetic field which then is tilted towards the axis of the strip.