Magnetic-field and quantum confinement asymmetry effects on excitons

A theoretical analysis and calculation of the excitonic states in asymmetric quantum dots is carried out in the presence of magnetic fields. The lack of rotational symmetry, introduced by strains and structural factors, produces splittings of the excitonic states with corresponding consequences on the optical oscillator strengths and polarization dependence. For example, we find that the asymmetry produces Zeeman splittings that are smaller than those for symmetric dots at small fields, which could be used as an additional diagnostic of the geometry of the structure. We focus our calculations on naturally occurring quantum dots due to layer fluctuations in narrow quantum wells. Moreover, we observe that increasing magnetic fields produce an interesting crossover to pure angular momentum states for all the excitonic eigenstates, regardless of the degree of asymmetry of the dots and their size. Explicit calculations of photoluminescence excitation yields are presented and related to the different degrees of freedom of the system.