Correlations Between Ground and Excited State Spectra of a Quantum Dot

The ground and excited state spectra of a semiconductor quantum dot with successive electron occupancy were studied with linear and nonlinear magnetoconductance measurements. A direct correlation was observed between the m th excited state of the N -electron system and the ground state of the ( N + m )-electron system for m up to 4. The results are consistent with a single-particle picture in which a fixed spectrum of energy levels is successively filled, except for a notable absence of spin degeneracy. Further departures from the single-particle picture due to electron-electron interaction were also observed. Magnetoconductance fluctuations of ground states show anticrossings where wave function characteristics are exchanged between adjacent levels.