On the Crossover from BCS Superconductivity to Bose Condensation
R. Micnas
Institute of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
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Received: November 16, 2001
We outline a microscopic approach to the superconducting fluctuations and pairing correlations in the attractive Hubbard model above Tc, using the functional integral method. A crossover from BCS superconductivity to Bose condensation of preformed pairs is studied by constructing the appropriate Ginzburg--Landau functionals. The differences between the lattice and the continuum models are discussed. The case of quasi-two-dimensional superconductors as well as the model with non-local pairing interaction are also examined. The effects of Gaussian fluctuations of the order parameter are analyzed in the T-matrix approach, the self-consistent Hartree approach and finally within the Ginzburg--Landau theory. Similarities with a paramagnon theory of itinerant-electron magnetism are pointed out.
DOI: 10.12693/APhysPolA.100.177
PACS numbers: 74.20.--z