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Current Dependence of the Energy Gap in Superconductors: A Direct Measurement


Mitescu, Catalin Dan (1966) Current Dependence of the Energy Gap in Superconductors: A Direct Measurement. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/7c8f-ya60.


From the tunneling characteristics of a tin-tin oxide-lead junction, a direct measurement has been made of the energy-gap variation for a superconductor carrying a current in a compensated geometry. Throughout the region investigated – several temperatures near Tc and down to a reduced temperature t = 0.8 –the observed current dependence agrees quite well with predictions based on the Ginzburg-Landau-Gor’kov theory. Near Tc the predicted temperature dependence is also well verified, though deviations are observed at lower temperatures; even for the latter, the data are internally consistent with the temperature dependence of the experimental critical current. At the lowest temperature investigated, t = 0.8, a small “Josephson” tunneling current allowed further a direct measurement of the electron drift velocity at low current densities. From this, a preliminary experimental value of the critical velocity, believed to be the first reported, can be inferred in the basis of Ginzburg-Landau theory. For tin at t = 0.8, we find vc = 87 m/sec. This value does not appear fully consistent with those predicted by recent theories for superconductors with short electronic mean-free-paths.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Physics)
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Mercereau, James E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:19 May 1966
Funding AgencyGrant Number
Standard Oil Company of CaliforniaUNSPECIFIED
Woodrow Wilson FoundationUNSPECIFIED
General Atomic FellowshipUNSPECIFIED
Record Number:CaltechTHESIS:10052015-153159106
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9201
Deposited On:06 Oct 2015 20:43
Last Modified:05 Mar 2024 22:34

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