Nobel Lecture: Type-II superconductors and the vortex lattice

their famous paper on the theory of superconductivity sGinzburg and Landau, 1950d. The approach was based on the general theory of the second-order phase transi-tions proposed by Landau in 1937 sLandau, 1937d. There Landau introduced the main variable, the so-called or-der parameter, which was finite below the transition and zero above it. Different phase transitions had different order parameters, and whereas it was evident for, e.g., the ferromagnetic transitions, namely, the spontaneous magnetization, it was far less evident for the supercon-ducting transitions. Ginzburg and Landu had a stroke of genius when they chose, as the order parameter, some sort of wave function. At that time nobody knew about Cooper pairs or about their Bose condensates, where all particles become coherent, i.e., described by the same