Indirect Exchange Interaction between two Quantum Dots in an Aharonov-Bohm Ring

TL;DR

This paper studies how magnetic interactions between two quantum dots in an Aharonov-Bohm ring are influenced by magnetic flux, revealing flux-dependent oscillations and correlations that affect spin states.

Contribution

It demonstrates how flux modulates RKKY interactions and Kondo correlations in a quantum dot system within an AB ring, highlighting flux-induced effects on spin coupling.

Findings

AB oscillation amplitude is enhanced by Kondo correlations in ferromagnetic RKKY.

A maximum appears at half flux where RKKY interaction is nullified.

Phase of AB oscillations shifts by pi in antiferromagnetic RKKY, indicating singlet formation.

Abstract

We investigate the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between two spins located at two quantum dots embedded in an Aharonov-Bohm (AB) ring. In such a system the RKKY interaction, which oscillates as a function of the distance between two local spins, is affected by the flux. For the case of the ferromagnetic RKKY interaction, we find that the amplitude of AB oscillations is enhanced by the Kondo correlations and an additional maximum appears at half flux, where the interaction is switched off. For the case of the antiferromagnetic RKKY interaction, we find that the phase of AB oscillations is shifted by pi, which is attributed to the formation of a singlet state between two spins for the flux value close to integer value of flux.