Kinetic exchange interaction in a narrow S-band

Abstract

A new canonical transformation is applied to the Hubbard Hamiltonian under strong correlation with arbitrary n to obtain an effective Hamiltonian which consists of both the itinerant property of electrons in split sub-bands and the Heisenberg-type spin-spin coupling. It reduces to that for a Heisenberg antiferromagnet as t/U to 0, but the intrasub-band electron hopping becomes important as t/U increases. This effective Hamiltonian is suitable for investigating the antiferro-paramagnetic transition.