Coreless Vortices in a Superconductor
Inside a superconductor, a magnetic field typically twists into tubes, vortices, each carrying one quantum of magnetic flux. That's how the classic Abrikosov lattice works. But in LiFeAs crystals, the picture is different.
Muon spectroscopy showed that the field penetrates not as individual vortices but as stripes. Each stripe contains pairs of 'coreless' vortices.