We consider the one dimensional (1D) extended Hubbard model at half filling in the presence of a magnetic field. Using field theory techniques we calculate the dynamical density-density correlation function χnn(ω,q) in the low-energy limit. When excitons are formed, a singularity appears in χnn(ω,q) at a particular energy and momentum transfer.
@article{arxiv.cond-mat/0204594,
title = {Dynamical density correlation function of 1D Mott insulators in a magnetic field},
author = {Davide Controzzi and Fabian H. L. Essler},
journal= {arXiv preprint arXiv:cond-mat/0204594},
year = {2009}
}