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Título del libro: Condensed Matter Theories
Título del capítulo: Intriguing role of hole-cooper-pairs in superconductors and superfluids

Autores UNAM:
MARCELA DOLORES GRETHER GONZALEZ; MANUEL DE LLANO DE LA GARZA;
Autores externos:

Idioma:
Inglés
Año de publicación:
2008
Palabras clave:

Bose-Einstein condensation; Electron-phonon coupling; Fermionic atom superuidity; Hole-Cooper-pairs; Superconductivity


Resumen:

The role in superconductors of hole-Cooper-pairs (CPs) are examined and contrasted with the more familiar electron-CPs, with special emphasis on their ?background? effect in enhancing superconducting transition temperatures Tc ? even when electron-CPs drive the transition. Both kinds of CPs are, of course, present at all temperatures. An analogy is drawn between the hole CPs in any many-fermion system with the antibosons in a relativistic ideal Bose gas that appear in substantial numbers only at higher and higher temperatures. Their indispensable role in yielding a lower Helmholtz free energy equilibrium state is established. For superconductors, the problem is viewed in terms of a generalized Bose-Einstein condensation (GBEC) theory that is an extension of the Friedberg-T.D. Lee 1989 boson-fermion BEC theory of high-Tc superconductors in that the GBEC theory includes hole CPs as well as electron-CPs ? thereby containing as well as further extending BCS theory to higher temperatures with the same weak-coupling electron-phonon interaction parameters. We show that the Helmholtz free energy of both 2e- and 2h-CP pure condensates has a positive second derivative, and are thus stable equilibrium states. Finally, it is conjectured that the role of hole pairs in ultra-cold fermionic atom gases will likely be negligible because the very low densities involved imply a ?shallow? Fermi sea. © 2009 by World Scientific Publishing Co. Pte. Ltd. All rights reserved.


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