Wavefunction and interaction effects in the addition spectrum of a Coulomb blockaded many electron quantum ring are investigated as a function of asymmetrically applied gate voltages and magnetic field. Hartree and exchange contributions to the interaction are quantitatively evaluated at a crossing between states extended around the ring and states which are more localized in one arm of the ring. A gate tunable singlet-triplet transition of the two uppermost levels of this many electron ring is identified at zero magnetic field.
@article{arxiv.cond-mat/0306667,
title = {Singlet-Triplet Transition Tuned by Asymmetric Gate Voltages in a Quantum Ring},
author = {A. Fuhrer and T. Ihn and K. Ensslin and W. Wegscheider and M. Bichler},
journal= {arXiv preprint arXiv:cond-mat/0306667},
year = {2007}
}