Critical current of mesoscopic superconducting devices
Abstract
Electron transport in superconducting devices has recently been discovered to be intimately related to mesoscopic physics. Both the Josephson effect and Giaever tunneling are mesoscopic phenomena. Just as a scattering theory of electrical conduction is widely used to obtain the electrical current in semiconductor nanostructures, a quantum mechanical scattering theory based on the Bogoliubov-de Gennes equations is developed to obtain the electrical properties of superconducting nanostructures. In this thesis I apply the scattering theory of electrical transport in superconductors to several outstanding problems in superconducting devices. I obtain the maximum supercurrent or 'critical current' which can flow through three different superconducting structures, namely (1) a one-dimensional superconductor-normal metal-superconductor (SNS) Josephson junction, (2) a quasi-one-dimensional superconducting wire and (3) a "quantum dot" structure containing one or two resonant tunneling levels. I also investigate (4) the control of Andreev bound states of an SNS junction by a normal metal probe, such as an scanning tunneling microscope tip or the gate electrode of a three-terminal SNS junction, which controls the critical current through an SNS junction. Finally I analyze (5) the effects of lateral confinement on the tunneling spectroscopy of d-wave superconductors, which should include the high $T\sb{c}$ superconducting perovskite compounds such as YBCO.
Degree
Ph.D.
Advisors
Bagwell, Purdue University.
Subject Area
Electrical engineering|Condensation
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