Dynamic Creation and Annihilation of Metastable Vortex Phase as a Source of Excess Noise

TL;DR

This paper proposes a novel noise mechanism in superconductors where a metastable vortex phase causes large voltage noise fluctuations, with the effect depending on sample geometry and vortex phase dynamics.

Contribution

It introduces the concept of dynamic creation and annihilation of metastable vortex phases as a source of excess noise in superconductors.

Findings

Excess noise correlates with the presence of a metastable vortex phase.

Reentrant behavior of noise is observed near the peak-effect region.

Noise disappears in Corbino geometry where vortex injection is prevented.

Abstract

The large increase in voltage noise, commonly observed in the vicinity of the peak-effect in superconductors, is ascribed to a novel noise mechanism. A strongly pinned metastable disordered vortex phase, which is randomly generated at the edges and annealed into ordered phase in the bulk, causes large fluctuations in the integrated critical current of the sample. The excess noise due to this dynamic admixture of two distinct phases is found to display pronounced reentrant behavior. In the Corbino geometry the injection of the metastable phase is prevented and, accordingly, the excess noise disappears