Plasmons in a strip with an anisotropic two-dimensional electron gas fully screened by a metal gate

Interest in anisotropic two-dimensional electron systems and in plasma oscillations in them has been growing recently. Plasmons in a strip with a two-dimensional electron gas with an elliptic Fermi surface that is located near a metal gate, which screens the fields of the two-dimensional gas, have been theoretically analyzed. The plasma eigenmodes in this system have been found analytically in the limit of strong screening and the frequencies and damping rates of these modes have been determined taking into account anisotropy, magnetic field, and electromagnetic retardation effects. It has been shown that the fundamental mode in this limit is an edge magnetoplasmon with a linear dispersion relation. The frequency, damping rate, and velocity of this magnetoplasmon are independent of the magnetic field, and the localization length near the edge is proportional to the magnetic field. The square of the frequency of any other mode is the sum of the square of the frequency of this plasma mode without magnetic field and the square of the cyclotron frequency with a coefficient, which is independent of the orientation of the conductivity tensor with respect to the edges of the strip but depends on the principal values of the effective mass tensor when electromagnetic retardation effects are taken into account.