A New Conception of Supraconductivity *

Abstract

5. According to these conceptions, there cannot exist any magnetic flux 'frozen' in the interior of pure supraconductors ; a permanent flux should only be found confined to the hollows of supra-conducting rings. The topological connectivity of a supraconductor, therefore, is a property extremely characteristic of its behaviour: the multiplicity of its connectivity, diminished by one, immediately indicates the number of independent conservative quantities, that is, of independent invariant magnetic fluxes. In 1937, Fritz London introduced his 'New Conception of Supraconductivity' to the readers of Nature. He proposed "representing all supracurrents realizable in a simply connected supraconductor by even one single electronic state". Some 20 years later, Bardeen, Cooper and Schrieffer built on this idea to produce the 'BCS theory' of superconductivity, which is based on a correlated, 'single-state' system of electron pairs. In 1938, London himself applied a similar idea to the phenomenon of superfluidity, suggesting that it may be a manifestation of bosonic condensation of atoms [see Nature 141 , 643-644 & Nature 141 (1938), 913 (1938)).