DYNAMICAL DENSITY-DENSITY CORRELATIONS IN ONE-DIMENSIONAL MOTT INSULATORS

The dynamical density-density correlation function is calculated for t he one-dimensional, half-filled Hubbard model extended with nearest-ne ighbor repulsion using the Lanczos algorithm for finite-size systems a nd analytically for large on-site repulsion compared to hopping amplit udes. At the zone boundary an excitonic feature exists for any finite nearest-neighbor repulsion and exhausts most of the spectral weight, e ven for parameters where no exciton is visible at zero momentum.