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Using single-electron capacitance spectroscopy, we map the magnetic field dependence of the ground state energies of a single quantum dot containing from 0 to 50 electrons. The experimental spectra reproduce many features of a noninteracting electron model with an added fixed charging energy. However, in detailed observations deviations are apparent: Exchange induces a two-electron singlet-triplet transition, self-consistency of the confinement potential causes the dot to assume a quasi-two-dimensional character, and features develop which are suggestive of the fractional quantum Hall effect.

The energy and the wave-vector dispersion of single-particle and collective excitations of the one-dimensional (1D) electron gas in GaAs quantum wires have been determined by resonant inelastic light scattering. In the 1D quantum limit the intrasubband plasmon displays the linear dispersion characteristic of 1D free-electron behavior. Quantitative agreement is found with calculations based on the random-phase approximation. In contrast, collective 1D intersubband excitations appear as dispersion-less and have a negligible shift from the single-particle energy

Nanometer-scale quantum wires have been directly produced using an epitaxial-growth technique. Modulation of the in-plane lattice constant of a GaAs/GaAlAs quantum well, grown over an InGaAs/GaAs strained-layer superlattice, laterally confines the carriers to one dimension. These novel structures are studied by luminescence and luminescence-excitation spectroscopies and by transmission electron microscopy. Large energy shifts and polarization anisotropy are observed. The results compare very well with a theoretical model based on the effective-mass approximation and elastic and phenomenological deformation-potential theories.

Inelastic light scattering spectra of the one-dimensional electron gas in GaAs quantum wires embedded in a strong perpendicular magnetic field show long-wavelength collective excitations and display multiple structures that indicate the magnetoroton density of states. The observed shift of the q∼0 intersubband magnetoplasmons from the cyclotron frequency is the signature of 1D behavior. At low temperatures spin polarization of the 1D system is revealed by the exchange enhancement of spin-flip excitations

We observe the capacitance signal resulting from single electrons tunneling into discrete quantum levels. The electrons tunnel between a metallic layer and confined states of a single disk in a microscopic capacitor fabricated in GaAs. Charge transfer occurs only for bias voltages at which a quantum level resonates with the Fermi energy of the metallic layer. This creates a sequence of distinct capacitance peaks whose bias positions directly reflect the electronic spectrum of the confined structure. From the magnetic field evolution of the spectrum, we deduce the nature of the bound states.