Resonance state in the 2D attractive Hubbard model

The systematic change of a resonance state with high momenta is studied wit h increasing particle density in the 2D attractive Hubbard model. Within th e conserving self-consistent T-matrix approximation, we present the spectra l functions for the one and two particle Green's functions as well as the s elf-energy. In the small density limit, the resonant state becomes stable a nd the result from the self-consistent calculations shows a good agreement with that from a simple analytical calculation. As particle density is incr eased, the resonance state acquires a short lifetime due to the increasing decay into two free particles. (C) 1999 Published Elsevier Science B.V. All rights reserved.