"Two-Fluid Model of Superconductivity", in Physical Review Letters, December 1, 1958

BARDEEN, John. "Two-Fluid Model of Superconductivity", in Physical Review Letters, December 1, 1958, volume 1/11, pp 399-400, In the original wrappers. Owner's name at top right corner of the front wrapper. Fine copy. "The famous Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity, for which the Nobel prize was awarded in 1972, was announced in 1957, before the creation of Physical Review Letters. Many papers following up on that theory subsequently appeared in PRL. In this paper Bardeen raises the question of the oft-made comparison between superconductivity and the superfluidity of liquid helium 4. The phenomenological two fluid (normal and superfluid) model of helium 4 introduced by Fritz London was applied to superconducting electrons as well, but the BCS theory justification for this was not obvious. Bardeen here shows that there is a basis for that comparison, based on reasonable approximations."--American Physical Society website for PRL Milestone papers.