Influence of the Amplitude in Lattice Modulation Spectroscopy

Within the Mott-insulating phase of the Hubbard model, linear-response calculations for a periodically modulated optical lattice depth clearly predict a resonance when modulated at a frequency equal to the Hubbard repulsion U. In this work we examine the effect of the amplitude of the lattice depth modulation on the threshold for excitation. Based on a recently developed strong-coupling approach to the non-equilibrium Hubbard model, we report results on the nonlinear regime and discuss effects of the amplitude as compared to the frequency for driving excitations into the upper Hubbard band.