Repulsion-to-attraction transition in correlated electron systems triggered by a monocycle pulse

We study the time evolution of the Hubbard model driven by a half-cycle or monocycle pulsed electric field F(t) using the nonequilibrium dynamical mean-field theory. We find that for properly chosen pulse shapes the electron-electron interaction can be effectively and permanently switched from repulsive to attractive if there is no energy dissipation. The physics behind the interaction conversion is a nonadiabatic shift delta of the population in momentum space. When delta similar to pi, the shifted population relaxes to a negative-temperature state, which leads to the interaction switching. Due to electron correlation effects delta deviates from the dynamical phase phi = integral dtF(t), which enables the seemingly counterintuitive repulsion-to-attraction transition by a monocycle pulse with phi = 0.