Type II superconductivity: Quest for understanding

By 1941, many of the essential experimental features of type II superconductivity had already been observed (de Haas and Voogd, Shubnikov et al., Keesom and Desirant). Moreover, truly remarkable progress had been made toward theoretical understanding based on negative interphase surface energy considerations (Gorter, H. London). However, a competing explanation, the filamentary sponge model, was proposed (Mendelssohn) in all attempt to explain magnetic hysteresis effects which tended to obscure the intrinsic thermodynamic character of type II superconductivity. This filamentary sponge model is now known to be of only very restricted applicability, but for more than two decades it enjoyed wide acceptance, so much so, that when the ultimate theoretical basis for type II superconductivity was formulated in the 1950\´s (Ginzburg and Landau, Abrikosov, Gorkov (GLAG)), it was largely ignored. With the discovery of the practical supermagnet potential of type II superconductors (Yntema, Kunzler et al.), interest in achieving deeper understanding of-high-magnetic-field superconductivity was reawakened. Only then was the power of the GLAG formalism very belatedly recognized, both with respect to near-ideal type II superconductors (Goodman) and with respect to non-ideal materials of technical interest (Berlincourt and Hake). Rapid experimental and theoretical progress followed on a number of significant aspects, including flux trapping, flux creep, and flux flow (Yntema, Anderson, Kim, Hempstead, Strnad), and surface superconductivity (Saint-James and de Gennes). Indirect "observation" of Abrikosov\´s vortex lattice was soon accomplished by neutron scattering techniques (Cribier et al.) and by nuclear magnetic resonance techniques (Pincus et al.). Finally, a more direct magnetic decoration technique (Essmann and Trouble) yielded remarkably graphic and incontrovertible pictoral confirmation of the Abrikosov vortex lattice.