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Absence of BCS Condensation of Atoms in a Repulsive Fermi Gas of Atoms

Fuxiang Han·Hailing Li·Minghao Lei·E Wu
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Abstract

Possible Bose-Einstein condensation of molecules and Bardeen-Cooper-Schrieffer (BCS) condensation of Cooper pairs of atoms in an ultracold Fermi gas of atoms with a repulsive two-body interaction are studied by using the path integral representation of the grand partition function. From the self-consistent equations obtained in the present work for the order parameters, we have found that BCS condensation of atoms can't occur in such a Fermi gas of atoms and that the condensate observed experimentally is composed of condensed molecules or possibly of preformed Cooper pairs. To substantiate our conclusions from the self-consistent equations for the order parameters, the effective atom-atom interaction mediated through molecules has also been computed with the Foldy-Wouthuysen transformation and has been found to be repulsive, which implies a net repulsive two-body interaction between atoms and hence the absence of BCS condensation of atoms.

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Fuxiang Han, Hailing Li, Minghao Lei, E Wu. 2005-10-11. Absence of BCS Condensation of Atoms in a Repulsive Fermi Gas of Atoms. https://arxiv.org/abs/cond-mat/0510296

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