Vortices give guidance

Landau's pupil, Alexei Abrikosov, realised almost immediately that Ginzburg and Landau's theory can also describe those superconductors (type II) that can coexist with strong magnetic fields. According to Abrikosov's theory this occurs because the superconductor allows the magnetic field to enter through vortices in the electron superfluid. These vortices can form regular structures, Abrikosov lattices, but disordered structures can also occur.

An Abrikosov lattice of vortices in a type-II superconductor. The magnetic field passes through the vortices.