Direct and indirect excitons and magnetic polarons inCdSe∕CdMgSe∕CdMnSesemimagnetic double quantum wells

Abstract

We have studied exciton photoluminescence and reflection spectra as well as formation of localized magnetic polarons and spin tunneling in $\mathrm{Cd}\mathrm{Se}∕\mathrm{Cd}\mathrm{Mg}\mathrm{Se}∕\mathrm{Cd}\mathrm{Mn}\mathrm{Se}$ asymmetric double quantum well structures with different barrier thicknesses. Measurements were performed in strong magnetic fields both in Faraday and Voigt configurations. Direct excitons from nonmagnetic CdSe and semimagnetic CdMnSe quantum wells were observed, as well as a spatially indirect exciton formed by the electron in the CdSe quantum well and the heavy hole in the CdMnSe one. The problem of the direct and indirect exciton forming localized magnetic polarons is addressed. Polarization properties of direct and indirect excitons are studied. In the case of a thin barrier, spin tunneling is observed under magnetic field. Calculations of the exciton energies are performed. The calculated values are found to be in reasonable agreement with the measured ones.