Spin Effects in a Quantum Ring

TL;DR

This paper reviews experiments on spin states in a quantum ring, using spectroscopy and magnetic/electric field responses to identify spin configurations, transitions, and exchange interactions in a many-electron quantum dot.

Contribution

It provides new insights into spin ground state sequences, identifies a gate-controlled singlet-triplet transition, and measures exchange interaction in a quantum ring.

Findings

Zeeman effect reveals spin ground state sequences

Identification of spin-paired orbital levels via magnetic and electric fields

Detection of gate-controlled singlet-triplet transition and exchange interaction size

Abstract

Recent experiments are reviewed that explore the spin states of a ring-shaped many-electron quantum dot. Coulomb-blockade spectroscopy is used to access the spin degree of freedom. The Zeeman effect observed for states with successive electron number allows to select possible sequences of spin ground states of the ring. Spin-paired orbital levels can be identified by probing their response to magnetic fields normal to the plane of the ring and electric fields caused by suitable gate voltages. This narrows down the choice of ground-state spin sequences. A gate-controlled singlet--triplet transition is identified and the size of the exchange interaction matrix element is determined.