Phase Fluctuations and Single Fermion Spectral Density in 2D Systems with Attraction

The effect of static fluctuations in the phase of the order parameter on the normal and superconducting properties of a 2D system with attractive four-fermion interaction is studied. Analytic expressions for the fermion Green's function, its spectral density, and the density of states are derived in the approximation where the coupling between the spin and charge degrees of freedom is neglected. The resulting single-particle Green's function clearly demonstrates a non-Fermi liquid behavior. The results show that as the temperature increases through the 2D critical temperature, the width of the quasiparticle peaks broadens significantly.