Generalized BEC in superconductivity

Abstract

A generalized Bose-Einstein condensation (GBEC) statistical theory of superconductors accounts not for BB interactions but rather for boson-fermion (BF) interactions. It extends the 1989 Friedberg-Lee BEC theory by including as bosons two-hole (2h) singlet Cooper pairs (CPs) in addition to the usual two-electron (2e) ones. It contains BCS theory when both kinds of pairs are equal in the BE condensate and in excited states-at least as far as identically reproducing the BCS gap equation for all temperatures T as well as the T = 0 BCS condensation energy for all couplings. As a ternary BF model with BF interactions, it yields T(c)s one-to-three orders-of-magnitude higher than BCS theory with the same Cooper/BCS model electron-phonon interaction. These T(c)s appear to be surprisingly insensitive to the BF interaction. (c) 2007 Elsevier B.V. All rights reserved.