Resistance in high-temperature superconductors

The effects of magnetic fields on high-temperature superconductors are considered. Lines of flux of magnetic fields in superconductors consist of whirlpools of electric current, or vortices, movement of which can impede the flow of electrons and increase the resistance of superconductors. Vortex movement under various temperature and magnetic field conditions is critical in controlling supercurrent flow. Research on superconductors and the microscopic theory of superconductivity are briefly reviewed. Three magnetic states of superconductors are described and magnetic phase diagrams are presented. Current flow and its interaction with type II superconductors are described. Vortex behavior and the formation of vortex liquid due to vortex lattice melting in high temperature superconductors is discussed. Superconductor microstructure, composition, pinning, and the effects of these factors on vortex solids are considered. Resistance in vortex lattices and vortex glass is discussed. An understanding of these vortex states will assist in the engineering of better superconducting materials. 5 refs