Tunneling and Transport in Ordered and Disordered Superconductors

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9303022 Goldman This research investigates the properties of disordered ultrathin films prepared by vapor deposition onto substrates held at liquid helium temperatures. The central focus is on disorder and magnetic-field-induced superconductor-insulator transitions. The physics underlying these transitions will be identified by mapping out the phase diagram in the space of the magnetic field, temperature, and disorder, bu determining critical exponents, and by investigating the transport and magnetotransport properties of the materials. The structures of the films will be investigated in situ via reflection high energy electron diffraction, and scanning tunneling microscopy. These studies will provide information about the nucleation and growth of the films. %%% This research studies the deposition, growth and physical properties of thin films of superconducting materials. Interestingly, the films lose their superconducting properties when a magnetic field is applied to them, and become isulators. The underlying physics of this dramatic change in electrical conductivity is not well understood, and a number of measurements are proposed to reveal important characteristics of the phenomena. The results will be of fundamental interest in the science of superconductivity. Additionally, the workers will investigate the structure and nucleation of the films, to see how the materials morphology relates to the observed properties. ***