Valence-bond analysis of half-filled Hubbard chains with long-range interelectronic interactions and on-site energy alternation.

Abstract

The extended Hubbard model with unscreened electron-electron interactions, modified to account for on-site energy alternation, is investigated through diagrammatic valence-bond technique. Exact results on finite-size systems are carefully extrapolated to the infinite-size system. The coupling of electrons to adiabatic phonons modulating on-site and on-bond energies is accounted for. The calculations give information on intrinsic site-charge-density-wave systems (e.g., mixed-stack charge-transfer crystals) but also allows one to investigate the site-charge-density-wave regime of an extended Hubbard chain without on-site energy alternation in the presence of electron-phonon coupling.