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Anticrossing-induced optical excitonic Aharonov-Bohm effect in strained type-I semiconductor nanorings

The exciton states in strained (In,Ga)As nanorings embedded in a GaAs matrix are computed. The strain distribution is extracted from the continuum mechanical model, and the exact diagonalization approach is employed to compute the exciton states. Weak oscillations of the ground exciton state energy with the magnetic field normal to the ring are an expression of the excitonic Aharonov-Bohm effect. Those oscillations arise from anticrossings between the ground and the second exciton state and can be enhanced by increasing the ring width. Simultaneously, the oscillator strength for exciton recombination exhibits oscillations, which are superposed on a linear increase with magnetic field. The obtained results are contrasted with previous theoretical results for 1D rings, and differences are explained to arise from different confinement potentials for the electron and the hole, and the large diamagnetic shift present in the analyzed type-I rings. Furthermore, our theory agrees qualitatively well with previous photoluminescence measurements on type-II InP/GaAs quantum dots.