Direct observation of quantum vortex fractionalization in multiband superconductors

TL;DR

This study reports the first direct observation of fractional quantum vortices in a multiband superconductor, revealing new quasiparticle behaviors and expanding understanding of vortex phenomena.

Contribution

It provides experimental evidence of vortex core fractionalization in a multiband superconductor using scanning tunneling microscopy, a novel observation in this field.

Findings

Observation of splitting of an integer-flux vortex into fractional vortices

Disparity between flux quanta and vortex cores

Demonstration of fractionalized core singularities in multiband superconductors

Abstract

Magnetic field is expelled from a superconductor, unless it forms quantum vortices, consisting of a core singularity with current circulating around it. The London quantization condition implies that there is one core singularity per quantum of magnetic flux in single-component superconductors, while in multiband materials fractional vortices are possible. Here, we report the first observation of quantum vortex core fractionalization on the potassium terminated surface of multiband superconductor KFe2As2 by scanning tunneling microscopy. We observe splitting of an integer-flux vortex into several fractional vortices, leading to disparity between numbers of flux quanta and vortex cores. Our findings demonstrate that fractionalized core singularities are possible in a multiband superconductor, opening avenue for new experimental platforms with quasiparticles with fractional statistics.