Observation of quantum vortex core fractionalization and skyrmion formation in a superconductor
- Yu Zheng
- Quanxin Hu
- Xin Yu
- Haijiao Ji
- Igor Timoshuk
- Julien Garaud
- Hanxiang Xu
- Yongwei Li
- Ye Gao
- Xingye Lu
- Vadim Grinenko
- Egor Babaev
- Noah F. Q. Yuan
- Rui Wu
- Baiqing Lv
- Chi-Ming Yim
- Hong Ding
2026-05-21
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.