Spin-singlet--spin-triplet oscillations in quantum dots

Two interacting electrons confined to a disk on a semiconductor surface are considered in a perpendicular magnetic field. As it is appropriate for experimental realizations, we use a two-dimensional harmonic-oscillator well to confine the electrons in the plane of the disk. We predict oscillations between spin-singlet and spin-triplet ground states as a function of the magnetic field strnegth. Phase diagrams describing this peculiar manifestation of the electron-electron interaction in a quantum dot are calculated for GaAs and experiments to verify them are proposed