Singlet-Triplet Transition Tuned by Asymmetric Gate Voltages in a Quantum Ring

TL;DR

This paper investigates how asymmetric gate voltages influence wavefunction interactions and induce a tunable singlet-triplet transition in a Coulomb blockaded quantum ring, revealing detailed interaction effects and state localization.

Contribution

It demonstrates a gate-controlled singlet-triplet transition at zero magnetic field in a quantum ring, with quantitative analysis of interaction contributions.

Findings

Identification of a gate-tunable singlet-triplet transition

Quantitative evaluation of Hartree and exchange interactions

Observation of state localization effects in the addition spectrum

Abstract

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.