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The retarding potential diode for energy gap measurements on superconductors.

McGill University
Publication Date
  • Physics.
  • Design
  • Physics


Starting with the Bardeen Cooper Schrieffer theory of a superconductivity, it is Shown how C. R. Crowell derived a work function difference between the normal and superconducting states, in terms of the energy gap of a superconductor, from the difference in the free energy between the states. The design and use of a retarding potential planar diode, and the associated circuitry required to observe temperature dependent work function changes near 4°K, are described. Measurements were carried out on a lead sample, above and below its superconducting transition temperature (7.2°K). The failure to observe work function changes related to superconductivity is discussed in terms of a different approach to the theory.

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