Modeling of Exciton Localization in Semimagnetic Concentric Double Quantum Ring by the Magnetic field

Abstract

The giant Zeeman splitting of the sigma+ and sigma- excitonic transitions and the exciton localization in a system of the concentric double quantum ring with a central barrier doped with magnetic ions is studied in the presence of an axial magnetic field using the variational principle in the effective mass approximation. The exchange interaction between the magnetic moments of the localized magnetic ions and the spins of the confined carriers is accounted via mean-field theory. The influence of the symmetric and asymmetric confinement along the radial direction of the quantum ring on the exciton energy is analyzed as a function of the outer ring radius keeping the radius of the inner ring to be constant. The intra-ring (direct) exciton localization can be forced to be in either of the two rings or oscillate between both rings by conveniently tuning the central barrier size separating the two rings or the applied magnetic field. The applied magnetic field significantly alters the potential barrier experienced by two different spin components of the exciton due to the influence of the magnetization of the DMS layer. The magnetic field is responsible for a system to transit from Type-I to Type-II, which eases electronic tunneling between the coupled rings, thereby changing the exciton's localization from intra-ring to inter-ring (indirect) and vice-versa.