Magnetooptics and dynamics of a magnetic polaron in semimagnetic CdSe/ZnMnSe quantum dots

The magnetooptics and picosecond dynamics of the radiative recombination of excitons in self-assembled semimagnetic CdSe/ZnMnSe quantum dots is studied at low temperatures. The behavior of individual quantum dots in a magnetic field and with an increase in temperature is indicative of a strong exchange interaction of excitons and magnetic Mn ions giving rise to a quasi-zero-dimensional exciton magnetic polaron. When the exciton energy exceeds the intracenter transition energy in Mn, the energy is rapidly transferred from excitons to Mn ions (faster than 20 ps). In the opposite case, a substantial red shift (~15 meV) of the emission line maximum is observed during the exciton lifetime ~500 ps, presenting the dynamics of the formation of a magnetic polaron with a characteristic time of ~110 ps.