Attractive Hubbard model and single-particle pseudogap due to classical pairing fluctuations in two dimensions

摘要

It is shown that in the two-dimensional attractive Hubbard model, themean-field phase transition is replaced by a renormalized classical regime offluctuations where a pseudogap opens up in the single-particle spectral weight.It is argued that this pseudogap and precursors of the ordered statequasiparticles can occur only in strongly anisotropic quasi two-dimensionalmaterials. This precursor phenomenon differs from preformed local pairs.Furthermore, while critical antiferromagnetic fluctuations would also lead to apseudogap in the repulsive model, there are some important differences betweenthe superconducting and magnetic pseudogap.