A hydrodynamic description of the collective excitations of an inhomogeneous electronic system is developed on the basis of the Thomas–Fermi–Dirac–von Weizsäcker approximation to the equilibrium ground state. This approximation allows one to define realistic equilibrium densities which are then used to obtain a consistent description of the dynamical behavior. An application to a parabolically confined electron gas is presented and the magnetoplasmon modes are obtained from a solution of the linearized hydrodynamic equations. The wave-vector dispersion of the modes is determined, as well as the detailed dependence on the orientation of the applied magnetic field. The power absorption in the long-wavelength limit is also calculated to illustrate the center-of-mass mode excitations probed by transmission experiments.

• Received 2 September 1993

DOI:https://doi.org/10.1103/PhysRevB.49.8147