Generalized Spin Susceptibility in the Narrow-s-Band Model

A calculation of the reduced spin susceptibility $\chi (q,\omega )$ of the paramagnetic phase of a system of electrons described by the narrow-$s$-band model is presented. The treatment is based on the two-pole approximation for electron correlation in narrow energy bands by Roth. An approximate expression for $\chi (q,\omega )$ in the strongly correlated limit is given. This expression is intended to be a valid approximation for the strongly correlated limit at higher carrier densities where low-density $T$-matrix results would be inapplicable.