Alonso, J.L.Boucaud, Ph.Martín Mayor, Víctorvan der Sijs, A.J.2023-06-202023-06-201998-06-010295-507510.1209/epl/i1998-00285-3https://hdl.handle.net/20.500.14352/60331© EDP Sciences. We are indebted to A. Muramatsu for very helpful remarks and stimulating discussions. We also acknowledge interesting discussions with A. Cruz, Ph. de Forcrand, J. M. De Teresa, J. G. Esteve, D. Frenkel, J. García, M. R. Ibarra, R. Mahendiran, R. Navarro, C. Rillo and especially G. Sierra. We thank L. A. Fernández, A. Tarancón and the others members of the RTNN collaboration for computing facilities. This work is financially supported by DGICYT (Spain), project AEN 96-1670, and by Acción Integrada Hispano-Francesa HF1996-0022.We present a relativistic spin-fermion model for the cuprates, in which both the charge and spin degrees of freedom are treated dynamically. The spin-charge coupling parameter is associated with the doping fraction. The model is able to account for the various phases of the cuprates and their properties, not only at low and intermediate doping but also for (highly) over-doped compounds. In particular, we acquire a qualitative understanding of high-Tc superconductivity through Bose-Einstein condensation of bound charge pairs. The mechanism that binds these pairs does not require a Fermi sea.engjournal articlehttp://dx.doi.org/10.1209/epl/i1998-00285-3http://iopscience.iop.orgopen access53Quantum Heisenberg-antiferromagnetHigh-temperature superconductorsScalar-fermion modelSpin correlationsBag mechanismPhase-diagramSymmetryState.Física-Modelos matemáticos