Microwave Absorption by Axisymmetric Plasmon Mode in 2D Electron Disk

Abstract

We theoretically analyze the frequency and damping of axisymmetric “dark” plasma mode in disk with 2D electron gas by calculating the absorption coefficient of an electromagnetic wave incident on the system. The problem is solved in a self-consistent approximation taking into account electromagnetic retardation. We use the Drude model for conductivity. The frequency of the axisymmetric plasmon depends on the electromagnetic retardation rather weakly compared with the case for infinite system since the plasma oscillations have zero dipole moment. The linewidth of the absorption resonance strongly changes depending on the ratio between the radiative and collisional decay. It is shown, that in the absence of collisions, the radiative decay rate is determined by the quadrupole moment of the axisymmetric plasma oscillations. In the lowest order by collisional and radiative decay, the linewidth is merely sum of the decays. In general case the collisional decay interplays with the radiative one that results in increase of the quality factor of the resonance.