Dissociation of vortex stacks into fractional-flux vortices

TL;DR

This paper explores how magnetic coupling in layered superconductors leads to fractional-flux vortices and predicts an evaporation transition where vortex stacks dissociate into fractional vortices, with an experimental proposal for detection.

Contribution

It introduces the concept of fractional-flux vortices in coupled superconducting layers and describes a transition involving their dissociation, advancing understanding of topological excitations in layered superconductors.

Findings

Fractional-flux vortices emerge due to modified transverse screening.

Vortex stacks undergo an evaporation transition at finite temperature.

An experimental setup with a bi-layer system can detect vortex dissociation.

Abstract

We discuss the zero field superconducting phase transition in a finite system of magnetically coupled superconducting layers. Transverse screening is modified by the presence of other layers resulting in topological excitations with fractional flux. Vortex stacks trapping a full flux and present at any finite temperature undergo an evaporation transition which corresponds to the depairing of fractional-flux vortices in individual layers. We propose an experiment with a bi-layer system allowing us to identify the dissociation of bound vortex molecules.