Figure 4: Illustration of the parametric resonance.
When a part of the initial bandwidth (red shaded region) for quasi-particle pairs lies in a parametric resonance (blue shaded regions), the corresponding modes grow exponentially, which leads to an exponentially growth of the effective mass meff(t). Accordingly the dispersion relation ωt(p) is shifted toward higher energies (light red shaded region). Once the quasi-particle bandwidth lies completely in between two regions of parametric resonance, the system stops absorbing energy in the leading order approximation. The parametric resonance at nΩ, n = 1, 2, … is only sharp in the limit of vanishing drive amplitude A and smears out with increasing A. For small A, the width of the resonance grows linearly with A.
