Optical excitations of a self-assembled artificial ion

By use of magnetophotoluminescence spectroscopy, we demonstrate bias-controlled single-electron charging of a single quantum dot. Neutral, single, and double charged excitons are identified in the optical spectra. At high magnetic fields one Zeeman component of the single charged exciton is found to be quenched, which is attributed to the competing effects of tunneling and spin-flip processes. Our experimental data are in good agreement with theoretical model calculations for situations where the spatial extent of the hole wave functions is smaller as compared to the electron wave functions.