Numerical study of spin effects in single and double quantum dots

Spin effects in single and vertically coupled double quantum dots are studied using an unrestricted self-consistent Hartree-Fock approximation. In a single dot, spin-parallel electrons occupy the two uppermost levels in magnetic fields, which leads to a cusp structure recently observed in the experiment in the magnetic-field dependence of addition spectra. In vertically coupled double dots, it is suggested that the absence of Hund's states observed in the experiment in the strongly coupled region is caused by the effect of dot thickness. In the intermediate region, we find high-spin states appear in the mixed shell of bonding and anti-bonding states. In the weakly coupled region, the pairing of addition spectra has been obtained. (C) 1998 Elsevier Science B.V. All rights reserved.