Magnetic excitation in the Hubbard-Hirsch model

Based on the Hubbard-Hirsch model, we studied the dynamical susceptibility and spin excitation of an itinerant-electron system within the random-phase approximation by using a Green’s-function technique. It is shown that the two-center matrix elements in the Hubbard-Hirsch model not only change the dynamic property of the susceptibility, but also widen the gap between two spin subbands, which suppresses the electron-hole single excitations. In contrast, the region of collective excitations of the spin becomes larger.