A generalized mean-field theory for the t-J model: the single-pole COM solution

We have reported the most general mean-field approximation for the t-J model obtained in the framework of the Composite Operator Method within the simplest one-pole approximation. The nearest-neighbor charge-charge and spin-spin correlators have been computed in a projection (one-loop) approximation with the result of reducing the self-consistent parameters just to two: the chemical potential and the kinetic energy. The properties of the system have been studied as functions of the filling and the temperature and compared with well established numerical results in order to assess the reliability of the obtained approximated solution. This latter is very well suited to study low-intermediate fillings and small dopings in case of frustration.