Observation of quantum vortex core fractionalization and skyrmion formation in a superconductor

Magnetic fields can penetrate a superconductor in the form of quantum vortices, which consist of a core singularity with circulating currents. London’s quantization implies that there is one core singularity per quantum of magnetic flux in single-component superconductors. Here, we report signatures of quantum vortex core fractionalization on the potassium-terminated surface of a multiband superconductor KFe 2 As 2 . The observed splitting of single integer-flux vortices into several fractional vortices results in a disparity between the numbers of flux quanta and vortex cores. These fractional vortices often arrange in chains, which calculations show are characterized by a ℂP 2 skyrmionic topological invariant; this constitutes a different type of topological defect: the chiral skyrmion. The disparate natures of integer and fractional vortices comprising skyrmions lead to distinct spectroscopic signatures.

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Publication Details

Journal
Science
Published
2026-05-21
DOI
https://doi.org/10.1126/science.ads0189
Primary Topic
Iron-based superconductors research
Type
article
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Observation of quantum vortex core fractionalization and skyrmion formation in a superconductor

Igor Timoshuk, Vadim Grinenko, Julien Garaud, Chi Ming Yim et al.
Science
Iron-based superconductors research
article

Observation of quantum vortex core fractionalization and skyrmion formation in a superconductor

Igor Timoshuk, Vadim Grinenko, Julien Garaud, Chi Ming Yim, Haijiao Ji, Yongwei Li, Quanxin Hu, EGOR BABAEV, X H Yu, HJ Xu, Ye Gao, Baiqing Lv, Yu Zheng, Rui Wu, Xingye Lu, Noah F. Q. Yuan, Hong Ding
article en

Abstract

Magnetic fields can penetrate a superconductor in the form of quantum vortices, which consist of a core singularity with circulating currents. London’s quantization implies that there is one core singularity per quantum of magnetic flux in single-component superconductors. Here, we report signatures of quantum vortex core fractionalization on the potassium-terminated surface of a multiband superconductor KFe 2 As 2 . The observed splitting of single integer-flux vortices into several fractional vortices results in a disparity between the numbers of flux quanta and vortex cores. These fractional vortices often arrange in chains, which calculations show are characterized by a ℂP 2 skyrmionic topological invariant; this constitutes a different type of topological defect: the chiral skyrmion. The disparate natures of integer and fractional vortices comprising skyrmions lead to distinct spectroscopic signatures.

Science
Université de Tours (FR), Centre National de la Recherche Scientifique (FR), Shanghai Jiao Tong University (CN), Chinese Academy of Sciences (CN), Beijing Normal University (CN), Hefei University (CN), Shanghai Advanced Research Institute (CN), Wallenberg Wood Science Center (SE), Institute of Physics (CN), National Laboratory for Superconductivity (CN), Institut Denis Poisson (FR), KTH Royal Institute of Technology (SE)
Openalex Percentile: Top 14%
Iron-based superconductors research
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