Density-matrix functional theory of strongly correlated lattice fermions -: art. no. 155118

A density-functional theory (DFT) of lattice fermion models is presented, which uses the single-particle density matrix gamma(ij) as basic variable. A simple, explicit approximation to the interaction-energy functional W[gamma] of the Hubbard model is derived from exact dimer results, scaling properties of W[gamma] and known limits. Systematic tests on the one-dimensional chain show a remarkable agreement with the Bethe-ansatz exact solution for all interaction regimes and band fillings. New results are obtained for the ground-state energy and charge-excitation gap in two dimensions. A successful description of strong electron correlations within DFT is achieved.