Manipulation of the electric state of the CdSe/ZnSe QD with a single Fe ²⁺ dopant

We demonstrate electrical control over the charge state of a CdSe/ZnSe quantum dot doped with a single Fe²⁺ion, enabling precise tuning of excitonic configurations and the determination of exchange interactions between the magnetic dopant and selected confined excitonic complexes. Using polarization-resolved magneto-photoluminescence spectroscopy, we systematically investigated the spin-dependent coupling between Fe²⁺and individual carriers across various excitonic charge states. By applying an external voltage, we stabilized neutral, negatively charged, and positively charged excitons, allowing controlled interaction with specific types and numbers of carriers. This electrical tunability offers new insights into exchange interactions manifesting optically as characteristic anticrossings and spin-dependent splittings in a magnetic field. These features enable the identification of excitonic complexes states, including multicharged species. Our findings establish a plug-and-play platform for manipulating spin interactions at the single ion-carrier level, advancing the development of electrically controlled solotronic devices and carrier-selective quantum information processing.