COLLECTIVE AND SINGLE-PARTICLE EXCITATIONS OF THE QUASI-ONE-DIMENSIONAL ELECTRON-GAS IN THE PRESENCE OF A MAGNETIC-FIELD

We investigate the collective and single-particle excitations of an el ectron gas, quantum confined in a quasi-one-dimensional quantum-well w ire, in the presence of a magnetic field. The calculations are done in the random-phase approximation with no further simplifying approximat ions. We derive analytical results for the dispersion relations of the intra- and intersubband magnetoplasmons. For large-magnetic fields th e dispersion curves of the intersubband magnetoplasmons approach the f requencies of the principal and Bernstein modes of a two-dimensional e lectron gas, whereas the dispersion curve of the intrasubband magnetop lasmon tends to zero in this limit. It is shown that additional inters ubband magnetoplasmons exist in comparison to a quasi-one-dimensional electron gas without a magnetic field and to a two-dimensional electro n gas in the presence of a magnetic field. These magnetoplasmons have the character of confined modes with a vanishing depolarization shift for zero- and infinite-magnetic fields. With these modes it is possibl e to explain the resonance-splitting and fine-structure effects in the recently observed far-infrared transmission spectra. We interpret the complete spectrum of the quasi-one-dimensional magnetoplasmons by the hybridization of confined principal and Bernstein modes. This spectru m is universal, i.e., independent from the concrete shape of the later al confining potential.