Exciton states in strongly coupled asymmetric semimagnetic double quantum dots
S. V. Zaitsev, M. K. Welsch+, A. Forchel+, G. Bacher*
Institute of Solid State Physics RAS, 142432 Chernogolovka, Moscov reg., Russia
+Technische Physik, Universität Würzburg, D-97074 Würzburg, Germany
*Lehrstuhl Werkstoffe der Elektrotechnik, Universität Duisburg-Essen, D-47057 Duisburg, Germany
PACS: 73.21.La, 75.50.Pp, 75.75.+a
Abstract
Exciton states in a pair of strongly coupled artificial
asymmetric quantum dots (QDs) have been studied in magnetic field
up to B=8 T by means of photoluminescence spectroscopy. The QD
molecules have been fabricated by a selective interdiffusion
technique applied to asymmetric CdTe/(Cd,Mg,Mn)Te double quantum
wells. The lateral confinement potential within the plane, induced
by the diffusion, gives rise to effective zero-dimensional exciton
localization. Incorporation of the Mn ions in only one dot results
in a pair of QDs with a markedly different spin splitting. In
contrast to a positive value of the exciton Lande g-factor in
nonmagnetic (Cd,Mg)Te-based single QDs, the ground exciton
transition in the nonmagnetic QD demonstrates nearly zero
g-factor, indicating a strong electron coupling between the dots.
New low-energy band with a strong red shift appears at high B
signifying formation of the indirect exciton, in accordance with
our calculations.