DYNAMIC-RESPONSE OF PARABOLICALLY CONFINED ELECTRON-SYSTEMS

The far-infrared response of electron systems confined in a parabolic potential is investigated experimentally. We present recent studies on cyclotron resonance, intersubband resonance and hybrid modes using va rious experimental techniques and geometries and compare our experimen tal findings with theoretical results based on a generalization of Koh n's theorem. We also focus on the far-infrared spectrum of so-called i mperfect parabolic wells with intentionally induced deviations from id eal parabolicity. Here, new symmetry-forbidden resonances are observed which yield a sensitive test for a theoretical description. At finite wavevector, intrasubband plasmonic excitations are also possible. We study their dispersion and investigate their interaction with the inte rsubband modes. If subjected to an in-plane magnetic field, the intras ubband plasmon exhibits a strongly anisotropic dispersion which can be directly related to so-called one-dimensional plasmons. Due to the si mplicity of the confining potentials, most of our experimental results can be explained in straightforward ways. Many of our results as well as the theoretical descriptions directly apply to recent investigatio ns of lateral nanostructures and thus may also serve for a better unde rstanding of this rapidly developing field.