APPROXIMATE TREATMENT OF A 2-DIMENSIONAL ANISOTROPIC PEIERLS-HUBBARD MODEL

A Green-function formalism is presented to study a Peierls-Hubbard Hamiltonian in two dimensions. The lattice consists of parallel dimerized chains with alternating nearest-neighbor hoppings t and t(parallel-to) and another hopping t(perpendicular-to) between different chains. The method treats the interdimer hopping as a perturbation and yields exact results in the uncorrelated case and for isolated dimers. The calculated spectral functions exhibit a number of narrow subbands with typical low-dimensional singularities. The dependence of the gap at the Fermi level on the electron-electron interaction U agrees qualitatively with the exact result in the known one-dimensional nondimerized limit. The paramagnetic susceptibility shows a maximum structure at low temperatures that is enhanced by U and by dimerization and a Curie-Weiss behavior at high temperatures.