CORRELATIONS BETWEEN GROUND AND EXCITED-STATE SPECTRA OF A QUANTUM-DOT

The ground and excited state spectra of a semiconductor quantum dot wi th successive electron occupancy were studied with linear and nonlinea r magnetoconductance measurements. A direct correlation was observed b etween the mth excited state of the N-electron system and the ground s tate of the (N + m)-electron system for m up to 4. The results are con sistent with a single-particle picture in which a fixed spectrum of en ergy levels is successively filled, except for a notable absence of sp in degeneracy. Further departures from the single-particle picture due to electron-electron interaction were also observed. Magnetoconductan ce fluctuations of ground states show anticrossings where wave functio n characteristics are exchanged between adjacent levels.