  We study the AC field induced current peaks of a spin blockaded double
quantum dot with spin-orbit interaction. The AC field modulates either the
interdot tunnel coupling or the energy detuning, and we choose the AC field
frequency range to induce two singlet-triplet transitions giving rise to two
current peaks. We show that for a large detuning the two current peaks can be
significantly stronger when the AC field modulates the tunnel coupling, thus
making the detection of the spin-orbit gap more efficient. We also demonstrate
the importance of the time dependence of the spin-orbit interaction.
