A theory for ihe high temperature superconductors is proposed. The dispersion of carriers in the 2D odel is calculated using numerical and analytical techniques, and compared with recent photo emission experimental results that reported a flat dis- fertion near the X and .Y points. Good agreement is observed between iheory and experiments. The density of states (DOS) of these dressed quasiparticles has a van Hove singularity. From the two carriers problem in an aniiferromagnei, an effec- iive Hamiltonian for holes is proposed. This effective model has superconductivity in ihe dxa_j3 channel, a critical temperature Tc ~ 100K at the optimal hole density, x = 0.15, and a qvasiparticle lifetime linearly dependent with energy. The appear-ance of an optimal concentration is a consequence of the van Hove singularity in the DOS. Other experimental results are also quantitatively reproduced by the theory. The present contribution is based on two recent papers by ihe authors (Phys. Rev. Lett: 73, 728 (1994) and NHMFL preprint, July 1994).
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