Single-particle and collective excitations in quantum wires made up of vertically stacked quantum dots: Zero magnetic field

TL;DR

This paper presents a theoretical study of electronic excitations in quantum wires composed of vertically stacked InAs/GaAs quantum dots, analyzing how structural parameters influence their excitation spectra and potential applications in quantum devices.

Contribution

It develops a comprehensive theoretical framework using the Bohm-Pines' RPA to analyze single-particle and collective excitations in vertically stacked quantum dot systems with a two-subband model.

Findings

Variation in barrier- and well-widths tailors excitation spectra.

The inverse dielectric function is crucial for understanding quantum transport.

Vertical stacking offers advantages over planar quantum dots for device applications.

Abstract

We report on the theoretical investigation of the elementary electronic excitations in a quantum wire made up of vertically stacked self-assembled InAs/GaAs quantum dots. The length scales (of a few nanometers) involved in the experimental setups prompt us to consider an infinitely periodic system of two-dimensionally confined (InAs) quantum dot layers separated by GaAs spacers. The the Bloch functions and the Hermite functions together characterize the whole system. We then make use of the Bohm-Pines' (full) random-phase approximation in order to derive a general nonlocal, dynamic dielectric function. Thus developed theoretical framework is then specified to work within a (lowest miniband and) two-subband model that enables us to scrutinize the single-particle as well as collective responses of the system. We compute and discuss the behavior of the eigenfunctions, band-widths, density of states, Fermi energy, single-particle and collective excitations, and finally size up the importance of studying the inverse dielectric function in relation with the quantum transport phenomena. It is remarkable to notice how the variation in the barrier- and well-widths can allow us to tailor the excitation spectrum in the desired energy range. Given the advantage of the vertically stacked quantum dots over the planar ones and the foreseen applications in the single-electron devices and in the quantum computation, it is quite interesting and important to explore the electronic, optical, and transport phenomena in such systems.