Dynamic Formation of Metastable Intermediate State Patterns in Type-I Superconductors

TL;DR

This study investigates how the intermediate state patterns in type-I superconductors depend on magnetic field ramp rate and specimen shape, revealing the influence of geometric barriers and flux tube dynamics.

Contribution

It demonstrates the sensitivity of intermediate state patterns to magnetic ramp rate and specimen geometry, highlighting the role of flux tube motion and geometric barriers.

Findings

Fast ramp rates produce laminar stripe patterns as flux tube imprints.

Flux tube phase is topologically favored in the intermediate state.

Geometric barriers influence the boundary between different phases.

Abstract

Structure of the intermediate state in type-I superconducting lead (Pb) is shown to be very sensitive to the ramp rate of an applied magnetic field. The configurations of resulting static patterns depend sensitively on the shape of the specimen. In particular, geometric barrier, present in the samples with rectangular cross-section, plays an important role in determining the sharp boundary between the phases of different topology. We propose that seemingly laminar (stripe) pattern obtained as a result of the fast field ramp is simply an imprint left behind by the fast-moving flux tubes. Our results confirm that flux tube phase is topologically favorable.