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The p-d model

A study of the p-d model by means of the COM is reported in Refs. [1,90,91,92,93]. In particular the following properties have been computed:

  1. The thermodynamic properties (i.e., chemical potential, double occupancy, local magnetic moment, hybridization) [90,93]

  2. The single-particle properties (i.e., energy spectra, density of states, Fermi surface, charge transfer susceptibility) [1,92,93]

The COM results have been compared with the ones obtained by:

The p-d model has been studied in the context of the COM by considering different approximations. The so-called reduced p-d model, where the transitions to the lower Hubbard band are neglected, has been analyzed in Refs. [1,90,91]. In these papers different choices of the basic composite fields have been taken. In Ref. [1] the effect of the local antiferromagnetic correlations on the electronic properties, density of states and band dispersions, has been analyzed as a function of the hole doping. The chosen basic operators reproduce the exact single-site results.

In Ref. [90] the spin correlator has been self-consistently calculated by means of a sum rule with the content of the Pauli principle; the calculated local magnetic moment agrees well with the data obtained by numerical simulation.

In Ref. [91] we have enlarged the basic field by considering on the same foot both spin and charge correlations. As a result the set of equations to determine all the correlators closes and a fully self-consistent formulation is obtained.

The complete p-d model has been studied in Refs. [92,93] in a four-pole approximation. The density of states shows the Zhang-Rice singlet band situated around the chemical potential. The dispersion of this band gives a Fermi surface which is in good agreement with the experimental $ \emph{ARPES}$ results for $ LSCO$. Several quantities, the local magnetic moment, the chemical potential, the d- and p- particle densities and the charge-transfer susceptibility, are in excellent agreement with the numerical results.


next up previous
Next: The generalized Hubbard model Up: contents Previous: The antiferromagnetic solution
avella 2002-06-10