We study the far-infrared (FIR) response of quantum dots with a variable number Ns of electrons and a non-parabolic confinement in a magnetic field B. For few electrons we compare the results of a Hartree (H) and a Hartree-Fock (HF) approach with those obtained by an exact diagonalization of the few-particle Hamiltonian. A good qualitative agreement is found between the HF approximation and the exact calculation. The resonance spectra are fingerprints of the ground state of the electron system and depend therefore strongly on Ns and B. With an increasing number of electrons, the H- and the HF-calculations show new features evolving in the FIR spectra. These features resemble the non-local mode coupling effects observed in the magnetoplasmon dispersion of two- and one-dimensional systems marking the transition to a quasi-classical hydrodynamic behaviour.
Acknowledgements--We would like to thank D. Heitmann, P. Grambow, E. Vasiliadou and B. Meurer for fruitful discussions about experimentally observed FIR spectra on various quantum dots. Two of us (D. P. and V. G.) very much appreciate the intense and instructive discussions with A. H. MacDonald about the origin of the 2me-mode. This research was supported in part by the Icelandic Natural Science Foundation and the Bundesminister fiir Forschung und Technologic under contract number TK0375/2 as well as a NATO Collaborative Research Grant CRG921204.