Superconductivity is characterized by vanishing electrical resistance and magnetic flux expulsion. For conventional type II superconductors, the magnetic flux expulsion is incomplete in an applied magnetic field above a critical value and magnetic flux penetrates the bulk of the superconductor in discrete quantized magnetic flux tubes (vortices), each carrying a single quantum of flux (h/2e). Investigating the unconventional superconductor UPt3 with a scanning superconducting quantum interference device (SQUID) microscope, we observed mobile half-quantum vortices together with one quantum vortices. Cooling the material under a higher magnetic field revealed the presence of lines of magnetic contrast resembling domain walls. These observations agree with theoretical predictions for chiral superconductivity with a two dimensional complex order-parameter with sheets of half-quantum vortices separating domains of opposite order-parameter chirality.
@article{arxiv.2512.03908,
title = {Visualization of vortex sheets and half quantum vortices in the chiral odd-parity superconductor UPt$_{3}$},
author = {P. García-Campos and V. O. Dolocan and A. D. Huxley and D. Aoki and K. Hasselbach},
journal= {arXiv preprint arXiv:2512.03908},
year = {2025}
}