Microwave spectroscopy of spin-orbit coupled states: Energy detuning vs interdot coupling modulation

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.