Excitations from a filled Landau level in the two-dimensional electron gas

We consider an interacting two-dimensional electron system, with a uniform positive background, in a strong perpendicular magnetic field at zero temperature, under conditions where an integral number of Landau levels are filled and the Coulomb energy e2εl0 is smaller than the cyclotron energy ℏωc. The elementary neutral excitations may be described alternatively as magnetoplasma modes, or as magnetic excitons—i.e., a bound state of a hole in a …