Ground-state transition in few-electron quantum dots observed by magnetophotoluminescence

We have investigated electrostatically confined quantum dots containing a few electrons each. In zero magnetic field the photoluminescence (PL) reflects the few-electron density of states of such artificial atoms and we can resolve their energy levels. The magnetic-field dispersion of these quantum dot levels shows anticrossing behavior and sharp energy jumps which we identify as manifestations of a change of ground state in the dots. From our PL measurements we thus determine the size and sign of the electron-electron and final-state interactions within the quantum dots.