Size effects in the exchange coupling between two electrons in quantum wire quantum dots

TL;DR

This paper theoretically examines how the exchange coupling between two electrons in coupled quantum dots within a quantum wire diminishes with increasing distance and barrier height, highlighting size effects in quantum dot systems.

Contribution

It introduces a variational Heitler-London method to analyze size effects on exchange coupling in quantum wire quantum dots, aligning well with experimental data.

Findings

Exchange coupling decays exponentially with distance and barrier height.

Reducing wire diameter decreases wavefunction overlap and exchange coupling.

The variational method shows good agreement with experimental results.

Abstract

We theoretically investigate the properties of a two-electron system confined in the three-dimensional potential of coupled quantum dots formed in a quantum wire. For this purpose, we implement a variational Heitler-London method that minimize the system energies with respect to variational parameters in electron trial wavefunctions. We find that tunneling and exchange couplings exponentially decay with increasing inter-dot distance and inter-dot barrier height. In the quasi-one-dimensional limit achieved by reducing the wire diameter, we find that the overlap between the dots decreases, which results in a drop of the exchange coupling. We also discuss the validity of our variational Heitler-London method with respect to the model potential parameters, and compare our results with available experimental data to find good agreement between the two approaches.