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A generalized BEC picture of superconductors
Author(s) -
Grether M.,
de Llano M.,
Tolmachev V. V.
Publication year - 2012
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.24193
Subject(s) - superconductivity , boson , formalism (music) , bcs theory , physics , condensed matter physics , fermion , cooper pair , quantum mechanics , vertex (graph theory) , electron , mathematical physics , pairing , mathematics , combinatorics , musical , graph , visual arts , art
A recent re‐examination of BCS theory leads one to devise a generalized BEC formalism (GBEC), that is, essentially a boson‐fermion (BF) model containing three new ingredients: (i) Cooper pairs (CPs), in contrast to BCS pairs, as real bosons; (ii) BF vertex interactions (analogous to electron‐phonon vertices); and (iii) two‐hole CPs (2hCPs) accounted for along with two‐electron CPs (2eCPs). In addition to the usual normal phase at high‐enough temperatures T , three condensed phases emerge at lower temperatures with substantially higher T c s than BCS theory. These are: two pure BEC phases of 2eCPs and of 2hCPs as well as a mixed phase with both kinds of CPs. BCS theory is precisely recovered with a mixed phase of equal numbers of both kinds of CPs. In contrast to the well‐known BCS exponential rise from zero of T c as function of carrier‐number density the GBEC scheme exhibits the linear rise as function of doping as eminently observed in high‐ T c underdoped superconductors such as YBCO. © 2012 Wiley Periodicals, Inc.