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

A Green-function formalism is presented to study a Peierls-Hubbard Ham iltonian 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. Th e method treats the interdimer hopping as a perturbation and yields ex act results in the uncorrelated case and for isolated dimers. The calc ulated spectral functions exhibit a number of narrow subbands with typ ical low-dimensional singularities. The dependence of the gap at the F ermi 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 tem peratures that is enhanced by U and by dimerization and a Curie-Weiss behavior at high temperatures.