Interwell exciton relaxation in semimagnetic asymmetric double quantum wells
S. V. Zaitsev, A. S. Brichkin, P. S. Dorozhkin, G. Bacher*
Institute of Solid State Physics RAS, 142432 Chernogolovka, Russia
*Lehrstuhl Werkstoffe der Elektrotechnik, Universität Duisburg-Essen, D-47057 Duisburg, Germany
PACS: 75.50.Pp, 75.75.+a, 78.67.De
Abstract
Possibility of a magnetic field control of spectral and
polarization characteristics of exciton recombination is examined
in Cd(Mg,Mn)Te-based asymmetric double quantum wells. At low
fields, exciton transition in semimagnetic well is higher in
energy than that in nonmagnetic well and interwell exciton
relaxation is fast. In contrast, when the energy order of the
exciton transitions reverses at high fields, unexpectedly slow
relaxation of σ--polarized excitons from nonmagnetic well
to the σ+-polarized ground state in the semimagnetic well
is observed. Strong dependence of the total circular polarization
degree on the heavy-light hole splitting Δhh-lh in the
nonmagnetic well is found and attributed to the spin dependent
interwell tunneling controlled by exciton spin relaxation. Such a
slowing down of relaxation allows separation of oppositely
spin-polarized excitons in adjacent wells.