Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Physics and Astronomy


The critical current of cross type superconductor-normal metal-superconductor (SNS) junctions has been studied as a function of temperature, applied magnetic field, and junction geometry in order to understand the physical processes occurring in SNS Josephson junction devices. In the absence of an applied field, the critical current is found to follow the theory of de Gennes in the regime near the critical temperature where the theory applies. In small fields, Fraunhofer patterns of remarkable quality are obtained in the regime where self field effects are negligible. From the temperature dependence of the period of oscillation of these Fraunhofer patterns, the field penetration depth (lamda)(T) of the superconducting banks is inferred and the penetration depth is found to have the same functional temperature dependence as that predicted by the BCS theory. The resulting critical current surface, functions of temperature and applied parallel magnetic field, shows that quantum oscillations can be driven by temperature, in good agreement with theory. If the field is applied perpendicular to the plane of the junction the critical current is found to decrease monotonically with increasing fields, going as 1/H for large fields. The effects of individual misaligned trapped vortex pairs in the superconducting electrodes on the maximum Josephson current is examined. The critical current is found to decrease in discrete steps as more vortices are introduced into the junction. The critical;current vs. field curves for junctions containing trapped vortices are found to agree qualitatively with theory; *DOE Report IS-T-1130. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.



Digital Repository @ Iowa State University,

Copyright Owner

Samuel Lee Miller



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111 pages