Multiple particle-hole pair creation in the Fermi-Hubbard model by a   pump laser
  We study the Fermi-Hubbard model in the strongly correlated Mott phase under the influence of a harmonically oscillating electric field, e.g., a pump laser. In the Peierls representation, this pump field can be represented as an oscillating phase of the hopping rate $J(t)$, such that the effective time-averaged rate $\bar J$ is reduced, i.e., switching the pump laser suddenly is analogous to a quantum quench. Apart from this time-averaged rate $\bar J$, it is well known that the oscillating component of $J(t)$ can resonantly create particle-hole pairs if the pump frequency $\omega_{\rm pump}$ equals (or a little exceeds) the Mott gap. In addition, we find that it is possible to create multiple pairs if $\omega_{\rm pump}$ is near an integer multiple of the gap. These findings should be relevant for pump-probe experiments. 
Nicolai ten Brinke, Manuel Ligges, Uwe Bovensiepen and Ralf   Sch\"utzhold
quant-ph cond-mat.str-el