Impurity effects in quantum dots: Towards quantitative modeling

TL;DR

This paper investigates impurity effects in quantum dots, combining experimental measurements with theoretical modeling to understand how impurities influence the electronic spectrum and how electron interactions mitigate impurity effects under magnetic fields.

Contribution

It introduces a combined experimental and theoretical approach to model impurity effects in quantum dots, including single-electron spectra and many-electron interactions, with implications for quantum dot device design.

Findings

Good agreement between model and experimental spectra

Impurity effects are reduced at high magnetic fields with more electrons

Modeling captures irregularities due to broken symmetry

Abstract

We have studied the single-electron transport spectrum of a quantum dot in GaAs/AlGaAs resonant tunneling device. The measured spectrum has irregularities indicating a broken circular symmetry. We model the system with an external potential consisting of a parabolic confinement and a negatively charged Coulombic impurity placed in the vicinity of the quantum dot. The model leads to a good agreement between the calculated single-electron eigenenergies and the experimental spectrum. Furthermore, we use the spin-density-functional theory to study the energies and angular momenta when the system contains many interacting electrons. In the high magnetic field regime the increasing electron number is shown to reduce the distortion induced by the impurity.