Encounters with Vitaly, Nina, and the Ψ function

The Ψ function introduced by Ginzburg and Landau has been a turning point in the development of our understanding of superconductivity. Two of its consequences, which have been of particular importance in my work, are mentioned here. One is the Meissner screening of a magnetic field by a normal metal backed by a superconductor, one of the most striking manifestations of the proximity effect. The other one is the occurrence of large thermodynamical fluctuations near the critical temperature, in a range that has become experimentally accessible in the High Temperature superconductors due to their short coherence length, giving access to the pinning potential of these materials.