Effect of confinement potential shape on exchange interaction in coupled quantum dots

TL;DR

This study investigates how different shapes of confinement potentials in coupled quantum dots affect exchange interactions, revealing non-monotonic behavior and localization effects relevant for quantum computing.

Contribution

It introduces a parametrized two-centre power-exponential model to analyze exchange interactions in various quantum dot profiles, highlighting non-monotonic behavior and localization effects.

Findings

Exchange energy decreases with interdot distance for Gaussian potentials.

Non-monotonic exchange behavior observed for rectangular-like potentials.

Localized electrons in inner quantum dots cause large singlet-triplet splitting.

Abstract

Exchange interaction has been studied for electrons in coupled quantum dots (QD's) by a configuration interaction method using confinement potentials with different profiles. The confinement potential has been parametrized by a two-centre power-exponential function, which allows us to investigate various types of QD's described by either soft or hard potentials of different range. For the soft (Gaussian) confinement potential the exchange energy decreases with increasing interdot distance due to the decreasing interdot tunnelling. For the hard (rectangular-like) confinement potential we have found a non-monotonic behaviour of the exchange interaction as a function of distance between the confinement potential centres. In this case, the exchange interaction energy exhibits a pronounced maximum for the confinement potential profile which corresponds to the nanostructure composed of the small inner QD with a deep potential well embedded in the large outer QD with a shallow potential well. This effect results from the strong localization of electrons in the inner QD, which leads to the large singlet-triplet splitting. Implications of this finding for quantum logic operations have been discussed.