SINGLE-PARTICLE EXCITATIONS AND MANY-PARTICLE INTERACTIONS IN QUANTUMWIRES AND DOTS

We have investigated electronic excitations in GaAs-AlxGa1-xAs quantum wires, and dots by resonance Raman spectroscopy. We find for quantum dots and quantum wires three types of excitations; single-particle, sp in-density, and charge-density excitations (SPE's, SDE's, and CDE's, r espectively), Our experiments show that SPE's are enhanced under condi tions of extreme resonance, which indicates that energy-density fluctu ations are responsible for the excitation of unscreened SPE's. The hig h intensity of the SPE's allows a detailed analysis of collective effe cts in the zero- and one-dimensional electron systems.