Symmetries and optical transitions of hexagonal quantum dots in GaAs/AlGaAs nanowires

TL;DR

This paper develops a symmetry-based method to analyze electronic states and optical transitions in hexagonal GaAs quantum dots within nanowires, revealing that approximate symmetries largely determine their optical properties.

Contribution

A new postsymmetrization technique (PTCO) is introduced that simplifies symmetry analysis without modifying existing electronic structure codes.

Findings

The D6h symmetry is approximately preserved despite underlying crystal structure.

Electronic states can be understood through symmetry elevation to D6h.

Optical emission properties are mainly governed by approximate symmetries.

Abstract

We investigate the properties of electronic states and optical transitions in hexagonal GaAs quantum dots within AlGaAs nanowires. Such dots are particularly interesting due to their high degree of symmetry. A streamlined postsymmetrization technique based on class operators (PTCO) is developed which enables one to benefit in one run from the insight brought by the Maximal symmetrization and reduction of fields (MSRF) approach reported by Dalessi et al. [Phys. Rev. B 81, 125106 (2010)], after having solved the Schr\"odinger equation. Definite advantages of the PTCO are that it does not require having to modify any existing code for the calculation of the electronic structure, and that it allows to numerically test for elevated symmetries. We show in the frame of a 4-band k.p model that despite the fact that the D6h symmetry of the nanostructure is broken at the microscopic level by the underlying Zinc Blende crystal structure, the effect is quite small. Most of the particularities of the electronic states and their optical emission can be understood by symmetry elevation to D6h and the presence of approximate azimuthal and radial quantum numbers.