  Electron-positron pair production, in combined Sauter potential wells and an
oscillating one is imposed on a static Sauter potential, is investigated by
using the computational quantum field theory. We find that the gain number (the
difference of pair number under combined potentials to the simple addition of
pair number for each potential) of the created pairs depends strongly on the
depth of static potential and the frequency of oscillating potential. In
particular, it is more sensitive to the frequency compared with the depth. For
the low-frequency multiphoton regime, the gaining is almost positive and
exhibits interesting nonlinear characteristics on both depth and frequency. For
the single-photon regime, however, the gaining is almost negative and decreases
near linearly with depth while it exhibits an oscillation characteristic with
frequency. Furthermore, the optimal frequency and depth of gain number are
found and discussed.
