Magnetic-field evolution of collective excitations in AlGaAs/GaAs few-electron quantum dots in the mK regime.

Spin transitions and interactions in few-electron quantum dots (QDs) are investigated by resonant inelastic light scattering (ILS). Here we present the observation of inter-shell excitations in GaAs/AlGaAs QDs that are fabricated by combining e-beam nano-lithography with high quality reactive ion etching. The interpretation of the experimental results by numerical evaluations within a full configuration interaction approach highlights the importance of the exchange and correlation effects in these systems. We show that, under the impact of a perpendicular magnetic field, the evolution of electronic spin and charge inter-shell excitations at mK temperatures reveal that significant changes in the ground state occur even at moderate magnetic fields. These experiments demonstrate that ILS enables the study of few-electron effects in QDs under the extreme conditions of low temperatures and high magnetic fields.