  We study the effect of strong DC and pulsed electric fields on a Mott
insulating system with coupling to optical phonons. A DC field of the order of
the gap induces a metallic state characterized by polaronic features in the gap
region and a partially inverted population. In this quasi-steady state, the
field-induced doublon-hole production is balanced by a phonon-enhanced
doublon-hole recombination. The photo-excitation of carriers by a pulsed field
leads to similar modifications of the electronic structure in the gap region,
and an associated reduction of the doublon life-time. We demonstrate that the
field-induced localization of electrons effectively enhances the phonon
coupling, an effect which should be measureable with time-resolved
photoemission spectroscopy.
