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Axisymmetric plasma mode in two-dimensional disk
Axisymmetric "dark"plasma excitations had recently been observed in AlGaAs/GaAs heterostructures in a 2D disk. We theoretically analyze the frequency and damping of plasmon in the 2D disk by calculating the obsorption coefficient of an electromagnetic wave incident on the system. The problem is solved in the self-consistent approximation. Conductivity of the system has a Drude form. The frequency of the plasmon depends on electromagnetic retardation rather weakly compared with the dependence of the damping. The linewidth of the obsorbance resonance strongly changes its behaviour depending of the ratio between the coherence radiative and collisional decay. The radiative decay rate is unexpectedly high, despite the zero dipole moment of the axisymmetric mode.