Magnetic-field control of the exciton quantum beats phase in InGaAs/GaAs quantum dots

International audienceWe demonstrate here the phase control of the neutral exciton quantum beats in InGaAs/GaAs quantum dots. A longitudinal magnetic field is used as a tuning parameter to change the phase of the oscillations in a deterministic way. This effect arises from the competition between the Zeeman splitting and the electron/hole exchange interaction on the exciton dipole symmetry. To explore this mechanism, we have developed a pump-probe setup based on the optical heterodyne detection of the quantum dots reflectivity allowing one to measure the exciton dynamics from a small quantum dots ensemble (∼300). Particular attention is paid to give a detailed theoretical analysis of the measurements. The experimental results are in excellent agreement with the model