The theory of superconductivity was formulated by Bardeen, Cooper, and Schrieffer (1957) and is called the BCS theory. It very successfully describes the superconducting properties of weak superconductors, such as aluminum, which are weak because of the small strength of the electron—phonon interaction. Further refinements of the theory have led to the strong coupling theory of Eliashberg (1960) which describes well the properties of superconductors such as lead. The distinction between aluminum and lead is roughly determined by the value of the electron—phonon mass enhancement factor λ., as shown by McMillan (1968). The BCS theory is discussed first. It must rank as one of the great successes of many-body formalism, since the theory provides detailed agreement with experiments. This agreement is a refreshing change from most comparisons between many-body theory and experiment, where the results often depend upon vertex corrections, correlations, and computer simulations. The beauty of BCS is that it is, mathematically, a simple theory which is exceedingly accurate. The reason it works is that the basic coupling forces are weak, and mean field works well.
KeywordsFermi Surface Tunnel Junction Electron Tunneling Josephson Current Energy Denominator
Unable to display preview. Download preview PDF.
- Allen, R B., and B. Mitrovic, in Solid State Physics, Vol. 37, eds. H. Ehrenreich, F. Seitz, and D. Turnbull ( Academic Press, New York, 1982 ), pp. 1–82.Google Scholar
- Baker, G. A., Jr., Essentials of Padé Approximants (Academic Press, New York, 1975 ).Google Scholar
- Eliashberg, G. M., Sov Phys. JETP 11, 696 (1960).Google Scholar
- Fiske, M. D., unpublished (1978).Google Scholar
- Halperin, B. I., and T. M. Rice, in Solid State Physics, Vol. 21, eds. H. Ehrenreich, F. Seitz, and D. Turnbull ( Academic Press, New York, 1968 ), p. 115.Google Scholar
- Keldysh, L. V, and Y. V. Kopaev, Sov Phys. Solid State 6, 2219 (1965).Google Scholar
- Kittel, C., Introduction to Solid State Physics, 3rd ed. ( Wiley, New York, 1966 ), p. 458.Google Scholar
- Mahan, G. D., 163, 612 (1967).Google Scholar
- Parks, R. D., ed., Superconductivity, Vols. I and II (Dekker, New York, 1969 ).Google Scholar
- Schrieffer, J. R., Theory of Superconductivity (Benjamin, Reading, Mass., 1964 ).Google Scholar