Far-Infrared Excitations in an Antidot at Finite Magnetic Fields

Abstract

We have investigated the far-infrared dipole modes of an antidot submitted to a perpendicularly applied magnetic field B. The ground state of the antidot is described in local spin-density functional theory, and the spectrum in time-dependent local spin-density functional theory. The results are compared with those corresponding to a quantum dot of similar electronic surface density. The method is able to reproduce two of the more salient experimental features, namely, that the main bulk and edge modes have the same circular polarization, and that the negative B dispersion edge branch oscillates, with minima at the B values corresponding to fully occupied Landau levels. It fails, however, to achieve the unique feature of short-period antidot lattices that the energy of the edge magnetoplasmon approaches the cyclotron frequency for small B values. The existence of anticyclotron-polarized bulk modes is discussed, and a detailed account of the dipole spin mode is presented.