title: Singlet-triplet transition tuned by asymmetric gate voltages in a quantum ring.
abstract: Wave-function 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.
authors.affiliation: Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Fuhrer
authors.forename: T
authors.initials: T
authors.lastname: Ihn
authors.forename: K
authors.initials: K
authors.lastname: Ensslin
authors.forename: W
authors.initials: W
authors.lastname: Wegscheider
authors.forename: M
authors.initials: M
authors.lastname: Bichler