SPECTRAL WEIGHT FUNCTION FOR THE HALF-FILLED HUBBARD-MODEL - A SINGULAR-VALUE DECOMPOSITION APPROACH

The singular value decomposition technique is used to reconstruct the electronic spectral weight function for a half-filled Hubbard model wi th on-site repulsion U = 4t from quantum Monte Carlo data. A two-band structure for the single-particle excitation spectrum is found to pers ist as the lattice size exceeds the spin-spin correlation length. The observed bands are flat in the vicinity of the (0, pi), (pi, 0) points in the Brillouin zone, in accordance with experimental data for high- temperature superconducting compounds.