Spin exchange interaction with tunable range between graphene quantum dots

TL;DR

This paper investigates the tunable spin exchange interaction between electrons in graphene quantum dots, employing a theoretical model to analyze the indirect coupling mediated by delocalized states.

Contribution

It introduces a detailed theoretical framework for controlling spin interactions in graphene quantum dots using a two-impurity Anderson model and Schrieffer-Wolff transformation.

Findings

Derived an effective spin Hamiltonian for graphene quantum dots.

Compared different theoretical approaches to model spin exchange.

Showed tunability of the exchange interaction range.

Abstract

We study the spin exchange between two electrons localized in separate quantum dots in graphene. The electronic states in the conduction band are coupled indirectly by tunneling to a common continuum of delocalized states in the valence band. As a model, we use a two-impurity Anderson Hamiltonian which we subsequently transform into an effective spin Hamiltonian by way of a two-stage Schrieffer-Wolff transformation. We then compare our result to that from a Coqblin-Schrieffer approach as well as to fourth order perturbation theory.