A MODEL FOR THE DOPED COPPER-OXIDE COMPOUNDS

We present a relativistic spin-fermion model for the cuprates, in whic h both the charge and spin degrees of freedom are treated dynamically. The spin-charge coupling parameter is associated with the doping frac tion. The model is able to account for the various phases of the cupra tes and their properties, not only at low and intermediate doping but also for (highly) over-doped compounds. In particular, we acquire a qu alitative understanding of high-T-c superconductivity through Bose-Ein stein condensation of bound charge pairs. The mechanism that binds the se pairs does not require a Fermi sea.