The Current Carried by Bound States of a Superconducting Vortex

TL;DR

This paper studies the quasiparticle excitations in superconducting vortex cores, revealing that localized Andreev bound states carry the current, which differs from the behavior in dirty superconductors.

Contribution

It demonstrates that in clean layered superconductors, vortex core currents are carried by Andreev bound states, contrasting with normal electron conduction in dirty superconductors.

Findings

Localized Andreev bound states carry the vortex current.

Core properties differ between clean and dirty superconductors.

Spectral current density analysis supports the bound state conduction mechanism.

Abstract

We investigate the spectrum of quasiparticle excitations in the core of isolated pancake vortices in clean layered superconductors. Analysis of the spectral current density shows that both the circular current around the vortex center as well as any transport current through the vortex core is carried by localized states bound to the core by Andreev scattering. Hence the physical properties of the core are governed in clean high-$\kappa$ superconductors (e.g. the cuprate superconductors) by the Andreev bound states, and not by normal electrons as it is the case for traditional (dirty) high-$\kappa$ superconductors.