Superconductivity in correlated systems: Constraint quantization of slave bosons

The quantization rules obtained by Le Guillou and Ragoucy in the slave part icle theories of correlated systems have been applied to study the supercon ductivity in extended Hubbard and t-J models. The quantization scheme has t he virtue of treating the local constraint exactly. We compare our numerica l results with those obtained in the mean-field approximation for usual sla ve boson technique. We also discuss the relation of the present approach wi th method of equation of motion for Hubbard operators. Where possible the o btained results are also compared with experimental data on high-temperatur e superconductors, as in these materials the essential physics is believed to depend on the presence of strong correlations. [S0163-1829(99)11913-1].