EVOLUTION OF THE SINGLE-PARTICLE SPECTRAL WEIGHT WITH DOPING

We have calculated the single-particle density of states N(omega) and the spectral weight A(p, omega) for the two-dimensional Hubbard model by combining quantum Monte Carlo simulations with the maximum-entropy analytic continuation technique. We present results for various values of the doping, temperature, and Coulomb repulsion U. At half-filling an insulating gap separates incoherent lower and upper Hubbard bands. In addition, narrow quasiparticle bands exist at the top of the lower Hubbard band and at the bottom of the upper Hubbard band. The bandwidt h of the quasiparticle bands is of order 2J, where J approximate to 4t (2)/U. Upon small doping, spectral weight is transferred from states a bove the insulating gap to the top of the lower Hubbard band, and a na rrow quasiparticle band of width similar to 4J forms. We find that the dispersion of this narrow band is similar to the results of the recen t angular resolved photoemission measurements of the hole doped cuprat es. We argue that the generic nature of the quasiparticle dispersion r elation observed in these materials arises from the strong Coulomb int eraction and reflects the hole-spin correlations rather than the one-e lectron interactions which customarily determine the band structure.