Fuhrer, A. and Ihn, Thomas and Ensslin, Klaus and Wegscheider, Werner and Bichler, Max
Singlet-Triplet Transition Tuned by Asymmetric Gate Voltages in a Quantum Ring.
Physical Review Letters 91 (20), p. 206802.
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.