Thermal Tuning and Inversion of Excitonic Zeeman Splittings in Colloidal Doped CdSe Quantum Dots

Variable-temperature magnetic circular dichroism (MCD) spectroscopy is used to measure excitonic Zeeman splittings in colloidal Co(2+)- and Mn(2+)-doped CdSe quantum dots with low dopant concentrations. The data demonstrate that the competition between intrinsic and exchange contributions to the excitonic Zeeman splittings in doped quantum dots can be tuned using temperature, from being dominated by exchange at low temperatures to being dominated by intrinsic Zeeman interactions at room temperature, with inversion at easily accessible temperatures and fields. These results may have relevance to spin-based information processing technologies that rely on manipulating carrier spins in quantum dots.