SPECTRAL DENSITY-FUNCTIONS FOR POLYACETYLENE WITHIN THE PEIERLS-HUBBARD MODEL

A Peierls-Hubbard Hamiltonian suitable for the description of polyacet ylene electronic structure is studied. We employ the Lanczos method to calculate the ground-state properties and single-particle spectral de nsity functions appropriate for the description of the photoemission a nd the inverse photoemission spectra. The data obtained confirm that t he dimerized polyacetylene is more stable than an undimerized one and elucidate how the Coulomb and the electron-phonon interactions open up a charge-transfer gap near the Fermi level. In particular we found th at the value of the gap increases when the electron-phonon interaction is switched on.