Local properties and Density of States in the two-dimensional p-d Model
  The p-d model which well describes the CuO_2 planes of the high-Tc superconductors is studied by means of the Composite Operator Method (COM). The relevant quasi-particle excitations are represented by composite operators. As a result of taking into account spin excitations we find a p- like band near the Fermi level. The dispersion of this band gives a Fermi surface which is in good agreement with the experimental measurements. Due to the strong mixing of the relevant excitations, the spectral weight of this band is reduced and gives a large Fermi surface in the moderately doped region. The dependence of the calculated physical quantities on model parameters, temperature and doping, is in a very good agreement with the available Quantum Monte Carlo results. 
V. Fiorentino, F. Mancini, E. Zasinas and A. F. Barabanov