Atomic Limit and Projected Hubbard Models for a Linear Chain

Abstract

The Hubbard model in the limit of infinite intrasite interaction and a related projected Hubbard model, which includes this extreme limit, are considered. This projected model is that portion of the full Hubbard model which preserves the number of sites of each possible occupancy, 0, 1, and 2. For the linear case, this projected model is solved exactly, both for the eigenvalue spectrum and the static thermodynamic properties. A second-order phase transition is found.