Reduction of fully screened magnetoplasmons in a laterally confined anisotropic two-dimensional electron system to an isotropic one
Phys. Rev. B 112, 075418 – Published 14 August, 2025
DOI: https://doi.org/10.1103/z6cw-hxx6
Abstract
We investigate the properties of natural two-dimensional (2D) magnetoplasma modes in laterally confined electron systems, such as 2D materials, quantum wells, and inversion layers in semiconductors with an elliptic Fermi surface. The resistivity of the system is considered in a dynamical anisotropic Drude model. The problem is solved in the fully screened limit, i.e., under the assumption that the distance between the two-dimensional electron system and the nearby metal gate is small compared to all other lengths in the system, including the wavelength of the plasmons. Remarkably, in this limit plasma oscillations in an anisotropic 2D confined system are equivalent to plasma oscillations in an isotropic 2D electron system obtained with some stretching, even when the electromagnetic retardation is taken into account. Moreover, accounting for electromagnetic retardation leads only to a renormalization of the effective masses of carriers, somewhat like for relativity. As an example, we reduce the equations describing plasmons in a gated disk with an anisotropic two-dimensional electron gas to the equations describing oscillations in an ellipse with isotropic Drude resistivity. In the absence of a magnetic field, we solve them analytically and find the eigenfrequencies. To find a solution in a magnetic field, we expand the current of plasma oscillations in the complete set of Mathieu functions. Leaving the leading terms of the expansion, we approximately find and analyze the magnetodispersion of the lowest modes.
