Date of Award
Doctor of Philosophy
Physics and Astronomy
D. K. Finnemore
A new family of superconductor--normal metal--insulator--superconductor (SNIS) Josephson junctions has been developed to study the motion of a single Abrikosov vortex under the influence of a Lorentz force from an applied transport current. The location of the vortex within the junction is determined by the diffraction pattern. Methods have been developed to nucleate a single vortex by applying a transport current in one strip of the junction and systematically to push the vortex to nearly any desired location within the juction by applying currents in either of the cross-strip legs of the junction. The vortex in thin film Pb was found to move stepwise from one pinning center to another. The average distance separating pinning centers in thin film Pb is about 1.0 [mu]m. The elementary pinning force f[subscript] p for a vortex in a pure Pb film was measured to be on the order of 10[superscript]-13 N at reduced temperature t = T/T[subscript] c = 0.9, which is about one order of magnitude smaller than that for a Pb-Bi film at this reduced temperature. The temperature dependance of f[subscript][rho] was found to be f[subscript][rho] ~ (1-T/T[subscript] c) above 6.5 K and f[subscript][rho] ~ (1-T/T[subscript] c)[superscript]2/3 below 6.5 K. The feasibility of using the motion of a single vortex to store information and perform logic has been investigated. Since the Josephson voltage is in the range of tens of millivolts, the read and write operations can be done with rather simple electronics.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Li, Qiang, "Single vortex motion and elementary pinning force in SNIS Josephson junctions " (1991). Retrospective Theses and Dissertations. 10050.