Electronic structures of(In,Ga)As∕GaAsquantum dot molecules made of dots with dissimilar sizes

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 lowers the degree of entanglement of the two electrons.

A Tight Binding Study of Strain-Reduced Confinement Potentials in Identical and Non-Identical InAs/GaAs Vertically Stacked Quantum Dots

“…This difference of the electronic structure at the large separations may have significant impact on the designing of the quantum gates using coupled quantum dot systems. The difference of the electronic structure is due to the atomistic crystal distortion that is not included in continuum methods and has recently been reported using an atomistic pseudo-potential method [10]. Our results qualitatively confirm the previously published results using an atomistic pseudo potential method, while our approach can scale to significantly larger systems of 52 million atoms [11,12,13].…”

“…Most of the work previously done [5,7] to analyze such closely coupled systems used continuum models such as effective mass and k•p which ignore such crystal symmetry and atomistic resolution. Only recently, an atomistic approach and pseudo-potential method for identical [8,9,11] and nonidentical dots have been used [10,11].…”

“…Most of the work previously done [5,7] to analyze such closely coupled systems used continuum models such as effective mass and k•p which ignore such crystal symmetry and atomistic resolution. Only recently, an atomistic approach and pseudo-potential method for identical [8,9,11] and nonidentical dots have been used [10,11].In this paper, a detailed description of strain and electronic structure of closely coupled identical and nonidentical quantum dot systems is presented using NEMO 3-D [12]. NEMO 3-D can atomistically simulate realistic systems as large as containing up to 52 million atoms [13,14].…”

Effect of confinement potential geometry on entanglement in quantum dot-based nanostructures

“…In QD systems entanglement could be controlled by externally applied electro-magnetic fields, 7 or by varying nanostructure parameters. Recently the effect of the interdot distance on the entanglement of two electrons trapped in (In,Ga)As/GaAs QD molecules has been studied, 8 as well as the effect of ionization on the entanglement of two electrons in a single QD. 9 In the present paper, we investigate how the geometrical changes in the confinement potential of single, core-shell and double QD structures influence the spatial entanglement 10 between two electrons trapped within the nanostructure.…”

Impurity effects in two-electron coupled quantum dots: entanglement modulation

“…There exists the possibility of manipulate the amount of entanglement in a QD molecule by controlling the nanostructure parameters that define the nanodevice. Zunger and He [23] studied the effect of interdot distance and asymmetry on the spatial entanglement of two-electron coupled quantum dots. They showed that the asymmetry in these systems significantly lowers the degree of entanglement of the two electrons.…”