Topological Hysteresis in the Intermediate State of Type-I Superconductors

TL;DR

This paper investigates the different topologies of the intermediate state in Type-I superconductors, revealing how flux tube and laminar patterns contribute to magnetic hysteresis through magneto-optical imaging and current distribution analysis.

Contribution

It introduces a detailed analysis of topological differences in the intermediate state and their role in magnetic hysteresis in Type-I superconductors.

Findings

Flux tubes form during magnetic field penetration.

Laminar patterns appear during flux exit.

Topological differences cause observable magnetic hysteresis.

Abstract

Magneto-optical imaging of thick stress-free lead samples reveals two distinct topologies of the intermediate state. Flux tubes are formed upon magnetic field penetration (closed topology) and laminar patterns appear upon flux exit (open topology). Two-dimensional distributions of shielding currents were obtained by applying an efficient inversion scheme. Quantitative analysis of the magnetic induction distribution and correlation with magnetization measurements indicate that observed topological differences between the two phases are responsible for experimentally observable magnetic hysteresis.