I. Equilibrium and Non-Equilibrium Superconducting Quantum Interference Phenomena. II. Applications of Superconducting Quantum Magnetometer

Citation

Wang, Run-Han (1975) I. Equilibrium and Non-Equilibrium Superconducting Quantum Interference Phenomena. II. Applications of Superconducting Quantum Magnetometer. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/wkq0-rh72. https://resolver.caltech.edu/CaltechTHESIS:05262023-012237053

Abstract

Experimental investigations were made on the equilibrium and nonequilibrium quantum interference phenomena in superconductors. A new instrument was developed for measuring magnetic susceptibility and moment with an improvement of sensitivity of nearly two orders of magnitude over the conventional magnetometers.

A quantitative determination was made on the relaxation rate of a perturbed superconducting phase to relax back to its equilibrium state. The temperature-dependent relaxation time is found to be consistent with the known quasiparticle relaxation time in nonequilibrium superconductors. The effect of relaxation processes on macroscopic quantum interference phenomena was observed for the first time through the temperature modulation of quantum interference in multiply connected superconducting circuits, and implies a modification of the Josephson frequency-voltage relationship. A relaxation model was developed and found adequate to account for nearly all the experimental results.

The development and performance of an ultrasensitive superconducting magnetometer instrument based on various unique properties of superconductors were discussed. Applications of this instrument over a temperature range of 200°K in the fields of magnetochemistry, paleomagnetism and the study of fluctuation effects in superconductivity were illustrated with actual data.

Thesis Files