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Experimental Studies of Weak Superconductivity


Kirschman, Randall Keenan (1972) Experimental Studies of Weak Superconductivity. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/y9wt-9r69.


Experimental investigations were made of the nature of weak superconductivity in a structure having well-defined, controllable characteristics and geometry. Controlled experiments were made possible by using a thin-film structure which was entirely metallic and consisted of a superconducting film with a localized section that was weak in the sense that its transition temperature was depressed relative to the rest of the film. The depression of transition temperature was brought about by underlaying the superconductor with a normal metal.

The DC and AC electrical characteristics of this structure were studied. It was found that this structure exhibited a non-zero, time-average supercurrent at finite voltage to at least .2 mV, and generated an oscillating electric potential at a frequency given by the Josephson relation. The DC V-I characteristic and the amplitude of the AC oscillation were found to be consistent with a two- fluid (normal current-supercurrent) model of weak super-conductivity based on e thermodynamically irreversible process of repetitive phase-slip, and featuring a periodic time dependence in the amplitude of the superconducting order parameter.

The observed linewidth of the AC oscillation could be accounted for by incorporating Johnson noise in the two-fluid model.

Experimentally it was found that the behavior of a short (length on the order of the coherence distance) weak superconductor could be characterized by its critical current and normal-state resistance, and an empirical expression was obtained for the time dependence of the super-current and voltage.

It was found that the results could not be explained on the basis of the theory of the Josephson junction.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Physics and Electrical Engineering)
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Minor Option:Electrical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Mercereau, James E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:10 November 1971
Funding AgencyGrant Number
Record Number:CaltechTHESIS:05022016-090342960
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9693
Deposited On:02 May 2016 16:58
Last Modified:01 Jul 2024 19:21

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