Dynamical Correlations after Pumping a Heisenberg Spin Ladder

We consider the dynamical correlations (as say could be measured in a time-resolved resonant inelastic x-ray scattering experiment) after pumping a Heisenberg spin ladder through varying in time its rung coupling with a square form pulse. We are able to treat this problem exactly through exploiting a Majorana fermion description of the ladders. The results showed unexpectedly rich time dependent behaviors, with rates controlled by external parameters as well as the duration of the pump. Our results can be related to experiments performed on photo-doped Mott insulators and shed new light on dynamics of simple spin systems far from equilibrium.