Electrical tuning of a semiconductor quantum dot enables precise control over its charge state and the resulting excitonic configurations. In a CdSe/ZnSe quantum dot doped with a single Fe²⁺ ion, the application of an external voltage allows stabilization of neutral, negatively charged, and positively charged excitons, providing access to controlled interactions between the magnetic dopant and individual carriers.
Using polarization-resolved magneto-photoluminescence spectroscopy, spin-dependent exchange interactions between Fe²⁺ and confined carriers can be probed across different charge states. These interactions manifest as characteristic anticrossings and spin splittings in a magnetic field, offering a clear optical fingerprint for identifying excitonic complexes, including multicharged species. The presence of the magnetic ion further enhances this identification, for example through distinctive cross-like features in the spectra that distinguish between positive and negative trions.
Electrical control also enables selective preparation of specific charge states, such as enforcing a purely negatively charged regime or inducing the appearance of positively charged excitons, which are otherwise difficult to observe in this material system. At the same time, while the charge state of the quantum dot can be tuned efficiently, the Fe dopant remains in the Fe²⁺ configuration, highlighting the challenge of controlling the ion’s charge state directly.
These results establish an electrically tunable platform for studying and manipulating spin interactions at the single ion–carrier level. Such systems are promising for solotronic applications, including single-spin devices and quantum information technologies.
Authors: Karolina Ewa Połczyńska, Aleksander Rodek, Tomasz Kazimierczuk, Zuzanna Ogorzałek-Sory, Piotr Kossacki and Wojciech Pacuski
Published 16 March 2026
