Singlet-triplet transition tuned by asymmetric gate voltages in a quantum ring.
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.
Fuhrer
A
A
Solid State Physics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.
Ihn
T
T
Ensslin
K
K
Wegscheider
W
W
Bichler
M
M