We have studied electron correlation effects in quantum dots and rings which include a repulsive scattering centre and are subjected to a perpendicular magnetic field. The results for the dipole-allowed absorption spectrum show good qualitative agreement with the observed magnetoplasmon dispersion in similar systems. This work provides a unified description of the electron correlations in quantum dots and quantum rings in a magnetic field. We also demonstrate that optical absorption is a direct route to explore the effects of impurity and interactions in a quantum ring.

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The ground states of parabolically confined electrons in a quantum dot are studied by both direct numerical diagonalization and quantum Monte Carlo ͑QMC͒ methods. We present a simple but accurate variational many-body wave function for the dot in the limit of a weak magnetic field. The wave function has the center-of-mass motion restricted to the lowest-energy state and the electron-electron interaction is taken into account by a Jastrow two-body correlation factor. The optimized wave function has an accuracy very close to the state-of-the-art numerical diagonalization calculations. The results and the computational efficiency indicate that the presented wave function combined with the QMC method suits ideally for studies of large quantum dots. ͓S0163-1829͑99͒07907-2͔