Pseudogap in the one-electron spectral functions of the attractive Hubbard model

We calculate the one-electron Green's function of the two-dimensional (2D) attractive Hubbard model by coupling the electrons to pair fluctuations. The latter are approximated by homogeneous amplitude fluctuations and phase correlations corresponding to the XY-model. The electronic density of states shows a pseudogap at temperatures well above the transition temperature Tc. For a quasi-3D system, a superconducting gap emerges out of the pseudogap below Tc.