Long-wavelength collective excitations in a two-dimensional spin-polarizedelectron gas: A phenomenological theory

The dispersion relations of the collective excitations induced in a 2D spin -polarized electron gas are derived within the framework of the Landau-Sili n theory applied to a two-component Fermi liquid. The quasiparticle interac tion is described by spin-dependent coefficients, which are parametric func tions of the initial degree of polarization. The motion of the low-energy e xcitations satisfies a semiclassical transport equation solved consistently with the Maxwell equations for the electromagnetic field produced by spin and charge fluctuations. The long-wavelength limit of the self-sustained os cillations is analyzed as a function of the initial degree of polarization of the system, preset by a de magnetic induction. [S0163-1829(98)01548-3].