Electrical transport in heterojunctions between unconventional superconductors: Application of the Green function formalism
Abstract
The primary objective of this work is to develop suitable techniques for the analysis and design of electronic devices based on semiconductor-superconductor heterostructures involving both conventional superconductors (like Niobium) and the high-$T\sb{c}$ superconductors (like YBCO, BSCCO). Much of the earlier theoretical work in this field was focused on simple idealized geometries. Our work has led to a sophisticated model that can be used to analyze arbitrary shaped mesoscopic structures with superconducting elements. This is a very powerful analytical tool that can include the effects of impurities, boundaries, phase-breaking, complicated band-structures and unconventional order parameters. It is now believed that high-$T\sb{c}$ superconductors have an order parameter that is fundamentally different from those in the conventional superconductors. Most importantly it seems quite likely that the order parameter changes sign for electrons with different k-vectors. This makes high-$T\sb{c}$ superconductors very sensitive to the presence of surfaces and boundaries which mis electronic states with different k. We have used our method to understand these effects by comparing our theory with experiments done on different high-$T\sb{c}$ junctions.
Degree
Ph.D.
Advisors
Datta, Purdue University.
Subject Area
Electrical engineering
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