Auger recombination of excitons in semimagnetic quantum dot structure in a magnetic field

Abstract

Magnetoluminescence of $\mathrm{Cd}\mathrm{Mn}\mathrm{Se}\text{\ensuremath{-}}\mathrm{Zn}\mathrm{Se}$ disk-shaped quantum dots in a magnetic field up to $11\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ is measured in the Faraday and Voigt geometries at liquid He temperatures and various levels of laser excitation. Within the range of $B=0--11\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ the intensity of the quantum dot photoluminescence increases strongly (up to two orders of magnitude) in the Faraday geometry and only slightly ($\ensuremath{\sim}1.5$ times) in the Voigt geometry. To explain the observed dependence on magnetic field direction the selection rules for the Auger recombination of excitons with excitation of Mn-ion are revised. The magnetic field dependence of the quantum yield of quantum dot exciton emission and its anisotropy are shown to appear due to the dependence of Auger recombination of uncharged excitons with excitation of Mn-ion on the spin of both exciton and Mn-ion. The anisotropy is provided by a quick spin relaxation of photoexcited excitons into the ground state which spin structure depends on the direction of the magnetic field.