Hartree-Fock approximation for response functions and collective excitations in a two-dimensional electron gas with filled Landau levels

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Abstract
The authors consider a two-dimensional interacting electron gas in a strong perpendicular magnetic field with an integral number of fully occupied Landau levels. An expression for the spin-dependent response function of this system has been derived in a Hartree-Fock approximation. Numerical results for the static polarisability have been obtained for one, two and three full Landau levels. Dispersion relations for the collective excitations of the system have been determined by locating poles in the response functions. Some conclusions are made concerning the reliability of the approximation by referring to the low-field limit.