Role of Impact Ionization in the Thermalization of Photoexcited Mott Insulators

We study the influence of the pulse energy and fluence on the thermalization of photodoped Mott insulators. If the Mott gap is smaller than the width of the Hubbard bands, the kinetic energy of individual carriers can be large enough to produce additional doublon-hole pairs via a process analogous to impact ionization. The thermalization dynamics, which involves an adjustment of the doublon and hole densities, thus changes as a function of the energy of the photo-doped carriers and exhibits two time scales: a fast relaxation related to the impact ionization of high-energy carriers and a slower time scale associated with higher-order scattering processes. The slow dynamics depends more strongly on the gap size and the photodoping concentration