Comparison of the electronic structure of the Hubbard and t − J models within the cluster perturbation theory

Electronic dispersion and density of states (DOS) have been calculated for the Hubbard model and the t - J and t - J* models with three-site correlated hopping by the cluster perturbation theory. We have found a rather strong quantitative difference both in dispersion and DOS at all doping for the Hubbard and t - J models at the energy scale omega [gap]t. The three-site correlated hopping addition results in an almost negligible difference for the Hubbard and t - J* models. Close to the Fermi energy, at the scale omega [lap]J, the electronic structure of all three models is similar. We have found the line of zeros of the Green function for the t - J model that has been previously obtained for the Hubbard model by cellular dynamical mean-field theory calculations.