Probing the singlet-triplet splitting in double quantum dots: Implications of the ac field amplitude

Abstract

We consider a double quantum dot whose energy detuning is controlled by an ac electric field. We demonstrate an energy configuration for which the ac-induced current flowing through the double dot directly probes the spin-orbit anticrossing point for small ac field amplitudes. On the contrary, as the ac amplitude increases a current antiresonance is formed, and the direct information about the spin-orbit interaction is lost. This result indicates that a large ac amplitude is not necessarily advantageous for the spectroscopy of spin-orbit coupled two-spin states. Moreover, we investigate the ac-induced current peaks versus the ac amplitude and show a current suppression when the ac field forms spin blocked states. This effect gives rise to a characteristic pattern for the current which can be controlled at will by tuning the ac amplitude. Our results can be explored by performing electronic transport measurements in the spin blockade regime.