Optical properties of a tip-induced quantum dot

We have performed optical spectroscopy measurements on a STM-tip-induced quantum dot in a GaAs layer. The dominant confinement in the (hole) quantum dot is found to be in the direction parallel to the tip axis. Electron confinement is achieved by a sub-surface AlGaAs barrier. Current-dependent measurements indicate that many-body interactions can cause spectral blueshifts up to 75 meV for a tunneling current of 10 nA. Consequently, a full treatment of the many-body problem is required for an accurate description of this type of system.