Filling and temperature dependence of the spin susceptibility of the two-dimensional Hubbard model in the superconducting d-wave phase

The two-dimensional Hubbard model in the superconducting d-wave phase has been solved within the Composite Operator Method (COM) in the two-pole approximation [1]. The unknowns of the theory have been computed exploiting the operatorial relations, dictated by the Pauli principle, existing between the composite operators belonging to the basis. Such a procedure has also allowed to correctly fix the Hilbert space of the problem avoiding to average on unphysical states and permitting to obtain a very good qualitative agreement with the experimental results available in the literature as regards the phase diagram in the T-n plane. Given such an encouraging result, in this short manuscript, we have analyzed the filling and temperature dependence of the static and uniform spin susceptibility, as obtained by means of the COM within a one-loop-like approximation, and we have compared them to the experimentally observed ones for single-layer high-Tc cuprate superconductors.