Quasiparticles in the spin-fermion model for CuO2 planes

The low-lying electron states in Mott-Hubbard insulators are quite well described using a self-consistent Born approximation in terms of spin-wave exchanges. This approach has been tested mainly in the context of the simplest (t-J) models. Here we present an extension to spin-ferrnion models, derived for realistic multiband models for the valence electrons in cuprate planes. The spectral functions show strong momentum dependences also at large energies, mimicking bandlike oxygen holes. In addition, a low-energy quasiparticle sector is found which can be interpreted in terms of propagating Zhang-Rice singlets. The quasiparticle dispersion is close to the one obtained with angular resolved photoemission in an insulating cuprate.