Dynamics of exciton magnetic polarons in CdMnSe/CdMgSe quantum wells: the effect of self-localization

摘要

We study the exciton magnetic polaron (EMP) formation in (Cd,Mn)Se/(Cd,Mg)Sediluted-magnetic-semiconductor quantum wells using time-resolvedphotoluminescence (PL). The magnetic field and temperature dependencies of thisdynamics allow us to separate the non-magnetic and magnetic contributions tothe exciton localization. We deduce the EMP energy of 14 meV, which is inagreement with time-integrated measurements based on selective excitation andthe magnetic field dependence of the PL circular polarization degree. Thepolaron formation time of 500 ps is significantly longer than the correspondingvalues reported earlier. We propose that this behavior is related to strongself-localization of the EMP, accompanied with a squeezing of the heavy-holeenvelope wavefunction. This conclusion is also supported by the decrease of theexciton lifetime from 600 ps to 200 - 400 ps with increasing magnetic field andtemperature.