Evolution of the single-particle spectral weight with doping

Abstract

We have calculated the single-particle density of states N( ω) and the spectral weight A( p, ω) 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 bandwidth of the quasiparticle bands is of order 2 J, where J ≈ 4t 2 U . Upon small doping, spectral weight is transferred from states above the insulating gap to the top of the lower Hubbard band, and a narrow quasiparticle band of width ~ 4 J forms. We find that the dispersion of this narrow band is similar to the results of the recent angular resolved photoemission measurements of the hole doped cuprates. We argue that the generic nature of the quasiparticle dispersion relation observed in these materials arises from the strong Coulomb interaction and reflects the hole-spin correlations rather than the one-electron interactions which customarily determine the band structure.