Magnetic field dependence of exciton fine structures in InAs/GaAs quantum dots: Exchange vs. Zeeman splittings

We have calculated the energies of the lowest four excitons (two bright states and two dark states) in an InAs/GaAs quantum dot under the longitudinal magnetic field, B. The calculations were carried out using the strain-dependent 8-band k·p theory and the configuration interaction method. At B=0, the electron–hole exchange interaction determines the splitting between the bright-state energies and that between the dark-state ones. The fine-structure splitting (bright-state splitting) is View the MathML source. At View the MathML source, the Zeeman effect determines both splittings which change linearly with B with different exciton g-factors for the bright and dark states. The transition from the exchange-dominant to Zeeman-dominant splittings occurs at View the MathML source, where the bright-state splitting deviates from the linear change near B=0. Due to the transition, the degree of circular polarization for the lower (upper) bright state changes from 0% to ≈100% (−100%).