Inelastic light scattering on few-electron quantum-dot atoms

We investigate InAs self-assembled quantum dots (SAQD) by resonant inelastic light scattering. By applying a gate voltage between a metallic front gate and a back electrode, we can charge the quantum dots with single electrons (1–6). With resonant inelastic light scattering, we can directly observe the elementary electronic excitations of the few-electron quantum-dot atoms, which are formed by the SAQD. We observe excitations which we identify as transitions of electrons from the s- to the p-shell (s–p transitions) and from the p- to the d-shell (p–d transitions) of the quasiatoms. We find that the s–p transition energy decreases when the p-shell is filled with 1–4 electrons. This can be explained as an effect of Coulomb interaction, which is confirmed by calculations of the few-electron system, using exact numerical diagonalization.