FLUX MOTION AND DISSIPATION IN HIGH-TEMPERATURE SUPERCONDUCTORS

Two quite different motivations spark the study of flux motion and resistance in the new high temperature superconductors. Achievement of usefully low resistance at usefully large current densities is the key to most practical applications, but conceptual understanding of the idealized resistive behavior in the zero current limit motivates much theoretical work. Some analyses emphasize the pinning of individual flux lines to inhomogeneities in the underlying material; others emphasize the collective aspects of the interacting flux lines, whether liquid, solid, crystalline, or glassy; still others emphasize the concept of percolative Josephson coupling between grains. An overview will be given of these various approaches, their interrelation, and the experimental evidence, including some new results on flux motion in large SNS arrays, treated as a model system.