  Production of electron-positron pairs from the quantum vacuum polarized by
the superposition of a strong and a perturbative oscillating electric-field
mode is studied. Our outcomes rely on a nonequilibrium quantum field
theoretical approach, described by the quantum kinetic Boltzmann-Vlasov
equation. By superimposing the perturbative mode, the characteristic resonant
effects and Rabi-like frequencies in the single-particle distribution function
are modified, as compared to the predictions resulting from the case driven by
a strong oscillating field mode only. This is demonstrated in the momentum
spectra of the produced pairs. Moreover, the dependence of the total number of
pairs on the intensity parameter of each mode is discussed and a strong
enhancement found for large values of the relative Keldysh parameter.
