Item – Theses Canada

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OCLC number
679504849
Link(s) to full text
LAC copy
LAC copy
Author
Nasmith, Benjamin Bruce.
Title
Extending the London theory to include steady-state electric fields in superconductivity.
Degree
M. Sc. -- Royal Military College of Canada, 2008
Publisher
Ottawa : Library and Archives Canada = Bibliothèque et Archives Canada, [2009]
Description
2 microfiches
Notes
Includes bibliographical references.
Abstract
The London theory of superconduction is a phenomenological theory designed to model the two major phenomena of superconduction: the persistence of supercurrent in the absence of an applied electric field and the expulsion of magnetic flux from the bulk of the material. The London theory also predicts that the electric field must vanish inside of steady-state superconductors. We show that the steady-state London theory of superconduction may be derived, using the variational principle, by minimizing the total system energy, consisting of the magnetic field energy and of the kinetic energy of the moving supercurrent. We further extend the London theory by minimizing the relativistic total energy, consisting of both electric and magnetic field energies, as well as the work done on the supercurrent by the fields. For typical superconducting materials, such as Lead and Indium, we show that the first order relativistic effects in the magnetic field are eleven orders of magnitude smaller than the applied magnetic field, for a 1 Tesla applied field. We also show that an external magnetic field induces an electric field within a steady-state superconductor. The steady-state electric field acts as a central force on the supercurrent, in addition to that of the magnetic field, directing it along closed paths. We show for the first time that the induced electric field and the Fermi pressure on electron gas determine the resulting charge distribution, which is characterized by two penetration depths. Lastly, we show that an external electric field penetrates beneath the surface of a superconductor to a depth where the Fermi pressure exactly opposes the force it exerts on the charges. Keywords: London theory of superconduction, magnetic flux expulsion, supercurrent, electric field
ISBN
9780494421253
0494421258