9508419 Kapitulnik A wide range of experiments will be conducted in order to obtain a better understanding of the global Temperature vs. Magnetic field phase diagram, as well as the kinetics associated with various phases of two dimensional and layered superconductors such as the high-temperature superconductors. The thermodynamics of the superconducting transition near the mean-field line, and the range of validity of the Lowest-Landau-Letel approximation to multilayers with various anisotropy will be investigated. Experiments on the melting of the two-dimensional vortex lattice will focus on different crossovers in the vortex dynamics as the length scales are being tuned. Superconductor-insulator transitions will be studied by varying systematically the degrees of screening and the Coulomb potential. The nature of the zero-field superfluid transition with increasing amount of disorder will also be investigated. The difference between weak and strong pinning will be sorted out by studying the role of disorder on the resistive transition and vortex dynamics. The variety of transport and magnetic measurements in the above experiments will provide the global phase diagram of the multilayers, this may uncover new glass phases and their incipient correlation. %%% High temperature superconductors are layered materials where superconductivity occurs in the copper-oxygen planes. They exhibit peculiar properties due to this two-dimensionality. This proposal investigates the resistive transition in magnetic fields, and the role of vortex structure and motion causing energy dissipation in high temperature superconductors and two dimensional superconductors in general. A broad range of experiments will be conducted on a model system of molybdenum-germanium/germanium multilayer in which the PI's have extensive expertise and capabilities of co ntrol and characterization. These experiments together will provide a better understanding of the phase diagram as well as the kinetics associated with the various phases of two-dimensional and layered superconductors. ***
