Approximate Treatment of a Two-Dimensional Anisotropic Peierls-Hubbard Model

Abstract

A Green-function formalism is presented to study a Peierls-Hubbard Hamiltonian in two dimensions. The 1attice consists of parallel dimerized chains with alternating nearest-neighbor hoppings t and t 11 and another hopping t 1 between different chains. The method treats the interdimer hopping as a perturbation and yields exact results in the uncorre1ated 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 levei 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 anda Curie-Weiss behavior at high temperatures.