Giant Excitonic Exchange Splittings at Zero Field in Single Colloidal CdSe Quantum Dots Doped with Individual Mn²⁺ Impurities.

Abstract

Replacing a single atom of a host semiconductor nanocrystal with a functional dopant can introduce completely new properties potentially valuable for "solotronic" information-processing applications. Here, we report successful doping of colloidal CdSe quantum dots with a very small number of manganese ions-down to the ultimate limit of one. Single-particle spectroscopy reveals spectral fingerprints of the spin-spin interactions between individual dopants and quantum-dot excitons. Spectrally well-resolved emission peaks are observed that can be related to the discrete spin projections of individual Mn²⁺ ions. In agreement with theoretical predictions, the exchange splittings are enhanced by more than an order of magnitude in these quantum dots compared to their epitaxial counterparts, opening a path for solotronic applications at elevated temperatures.