Electronic structures of (In,Ga)As/GaAs quantum dot molecules made of dots with dissimilar sizes

TL;DR

This study compares the electronic structures of heteropolar and homopolar (In,Ga)As/GaAs quantum dot molecules, revealing significant differences at large inter-dot distances and implications for electron entanglement.

Contribution

It provides a detailed comparison of heteropolar and homopolar quantum dot molecules using advanced computational methods, highlighting key differences in electronic structure and entanglement.

Findings

Hetero-QDMs show dot-localized orbitals at large distances.

Bonding-antibonding splitting differs significantly between hetero- and homo-QDMs.

Asymmetry increases double occupation and affects electron entanglement.

Abstract

Using single-particle pseudopotential and many-particle configuration interaction methods, we compare various physical quantities of (In,Ga)As/GaAs quantum dot molecules (QDMs) made of dissimilar dots (heteropolar QDMs) with QDMs made of identical dots (homopolar QDMs). The calculations show that the electronic structures of hetero-QDMs and homo-QDMs differ significantly at large inter-dot distance. In particular (i) Unlike those of homo-QDMs, the single-particle molecular orbitals of hetero-QDMs convert to dot localized orbitals at large inter-dot distance. (ii) Consequently, in a hetero-QMD the bonding-antibonding splitting of molecular orbitals at large inter-dot distance is significantly larger than the electron hopping energy whereas for homo-QDM, the bonding-antibonding splitting is very similar to the hopping energy. (iii) The asymmetry of the QDM increases significantly the double occupation for the two-electron ground states, and therefore affects the degree of entanglement of the two electrons.