Tight-binding simulations of random alloy and strong spin-orbit effects in InAs/GaBiAs quantum dot molecules
type: CreativeWork
description: Self-assembled \ce{InAs} quantum dots (QDs), which have long hole-spin coherence times and are amenable to optical control schemes, have long been explored as building blocks for qubit architectures. One such design consists of vertically stacking two QDs to create a quantum dot molecule (QDM). The two dots can be resonantly tuned to form "molecule-like" coupled hole states with the hybridization of hole states otherwise localized in each respective dot. Furthermore, spin-mixing of the hybridized states in dots offset along their stacking direction enables qubit rotation to be driven optically, allowing for an all-optical qubit control scheme. Increasing the magnitude of this spin-mixing is important for optical quantum control protocols. We introduce the incorporation of dilute \ce{GaBi_xAs_{1-x}} alloys in the barrier region between the two dots, as \ce{GaBiAs} is expected to provide an increase in spin-mixing of the molecular states over \ce{GaAs}. Using an atomistic tight-binding model, we compute the properties of \ce{GaBi_xAs_{1-x}} and the modification of hole states that arise when the alloy is used in the barrier of an \ce{InAs} QDM. We show that an atomistic treatment is necessary to correctly capture non-traditional alloy effects of \ce{GaBiAs}. Additionally, an atomistic model allows for the study of configurational variances and clustering effects of the alloy. We find that in \ce{InAs} QDMs with a \ce{GaBiAs} inter-dot barrier, hole states are well confined to the dots up to an alloy concentration of 7\%. By independently studying the alloy-induced strain and electronic scattering off \ce{Bi} and As orbitals, we conclude that an initial increase in QDM hole state energy at low Bi concentration is caused by the alloy-induced strain. Additionally, a comparison between the fully alloyed barrier and a partially alloyed barrier shows that fully alloying the barrier applies an asymmetric strain between the top and bottom dot. By lowering the energetic barrie…
abstract: Self-assembled \ce{InAs} quantum dots (QDs), which have long hole-spin coherence times and are amenable to optical control schemes, have long been explored as building blocks for qubit architectures. One such design consists of vertically stacking two QDs to create a quantum dot molecule (QDM). The two dots can be resonantly tuned to form "molecule-like" coupled hole states with the hybridization of hole states otherwise localized in each respective dot. Furthermore, spin-mixing of the hybridized states in dots offset along their stacking direction enables qubit rotation to be driven optically, allowing for an all-optical qubit control scheme. Increasing the magnitude of this spin-mixing is important for optical quantum control protocols. We introduce the incorporation of dilute \ce{GaBi_xAs_{1-x}} alloys in the barrier region between the two dots, as \ce{GaBiAs} is expected to provide an increase in spin-mixing of the molecular states over \ce{GaAs}. Using an atomistic tight-binding model, we compute the properties of \ce{GaBi_xAs_{1-x}} and the modification of hole states that arise when the alloy is used in the barrier of an \ce{InAs} QDM. We show that an atomistic treatment is necessary to correctly capture non-traditional alloy effects of \ce{GaBiAs}. Additionally, an atomistic model allows for the study of configurational variances and clustering effects of the alloy. We find that in \ce{InAs} QDMs with a \ce{GaBiAs} inter-dot barrier, hole states are well confined to the dots up to an alloy concentration of 7\%. By independently studying the alloy-induced strain and electronic scattering off \ce{Bi} and As orbitals, we conclude that an initial increase in QDM hole state energy at low Bi concentration is caused by the alloy-induced strain. Additionally, a comparison between the fully alloyed barrier and a partially alloyed barrier shows that fully alloying the barrier applies an asymmetric strain between the top and bottom dot. By lowering the energetic barrie…
author: Lin, Arthur
language: en
date published: 2023
date modified: 2026-07-24T03:02:13Z
provider: University of Maryland
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Maryland

PropertyValue
property ID: Handle
value: http://hdl.handle.net/1903/31752

PropertyValue
property ID: DOI
value: 10.13016/e8pl-i6ug