THEORY OF ELECTROMAGNETIC RESPONSE AND COLLECTIVE EXCITATIONS IN ANTIDOTS

The theory of collective excitations in a single antidot and in a syst em of interacting antidots is presented. The problem is solved within the framework of classical electrodynamics neglecting the nonlocal and retardation effects. It is shown that the spectrum of collective exci tations in a single antidot consists of two branches. The first mode c oincides with the single-particle cyclotron resonance omega=omega(c) t he second one is the edge magnetoplasmon (EMP) mode. The EMP mode has the vanishing damping (in the collisionless approximation) only at ome ga < omega(c). At omega > omega(c) it decays on account of emission of two-dimensional (2D) bulk magnetoplasmons to the surrounding 2D mediu m. The induced electric potential and charge density of the EMP mode h ave the form of outgoing cylindrical waves at omega > omega(c). As a c onsequence, the interantidot interaction cannot be neglected in an arr ay of antidots at omega > omega(c). Collective excitations in an array of interacting antidots are considered in the modified-dipole and eff ective-medium approximations. The results obtained explain the main fe atures of the antidot excitation spectrum observed in recent experimen ts.