THE RESPONSE FUNCTION OF A 2-DIMENSIONAL ELECTRON-GAS IN A UNIDIRECTIONAL SPATIALLY PERIODIC MAGNETIC MODULATION

The dynamical dielectric response function and collective excitations of a two-dimensional electron gas under a perpendicular magnetic field and in the presence of an additional weak unidirectional spatially mo dulated periodic magnetic field are calculated within the random-phase approximation. It is found that the dynamical dielectric response fun ction is not only broadened by the additional magnetic modulation, but it also contains a series of subsingularities at the band edges. Such broadening of the response function is also found to modify the magne toplasmon modes of such a system over their unmodulated counterpart. T he origin of the new subsingularities is attributed to the magnetic mo dulation-induced broadening of the energy spectrum. This broadening, b eing non-uniform, leads to the reintroduction of particle-hole excitat ions into the dielectric response function. Such fine structures at th e band edges are similar in appearance to those recently reported for the case of a weak unidirectional spatially modulated periodic electri c potential though however the former may be up to about an order of m agnitude larger in bandwidth compared to those seen for the electric c ase when equal modulation strengths are considered. It is therefore pr oposed that these new predicted fine structures should be more readily observed in far-infrared spectroscopy experiments over their electric counterpart.