SPIN AND CHARGE-DENSITY WAVES IN THE EXTENDED HUBBARD-MODEL - A SLAVE-BOSON APPROACH

We use the extended Hubbard model to investigate the properties of the charge- and spin-density-wave phases in the presence of a nearest-nei ghbors repulsion term in the framework of the slave-boson technique. W e show that, contrary to Hartree-Fock results, an instablity may occur for sufficiently high values of the Hubbard repulsion, both in the sp in- and charge-density-wave phase, which makes the system discontinuou sly jump to a phase with a smaller or zero wave amplitude. The limits of applicability of our approach are discussed and our results are com pared with previous numerical analysis. The phase diagram of the model at half-filling is determined.