Collective and Independent-Particle Motion in Two-Electron Artificial Atoms

Investigations of the exactly solvable excitation spectra of two-electron quantum dots with a parabolic confinement, for different values of the parameter $R_W$ expressing the relative magnitudes of the interelectron repulsion and the zero-point kinetic energy, reveal for large $R_W$ a rovibrational spectrum associated with a linear trimeric rigid molecule composed of the two electrons and the infinitely heavy confining dot. This spectrum transforms to that of a “floppy” molecule for smaller $R_W$. The conditional probability distribution calculated for the exact two-electron wave functions allows identification of the rovibrational excitations as rotations and stretching/bending vibrations.