  Using the Kadanoff-Baym-Keldysh formalism, we employ nonequilibrium dynamical
mean-field theory to exactly solve for the nonlinear response of an
electron-mediated charge-density-wave-ordered material. We examine both the dc
current and the order parameter of the conduction electrons as the ordered
system is driven by the electric field. Although the formalism we develop
applies to all models, for concreteness, we examine the charge-density-wave
phase of the Falicov-Kimball model, which displays a number of anomalous
behaviors including the appearance of subgap density of states as the
temperature increases. These subgap states should have a significant impact on
transport properties, particularly the nonlinear response of the system to a
large dc electric field.
