Electron localization and optical absorption of polygonal quantum rings

TL;DR

This paper theoretically studies polygonal quantum rings, especially triangular ones, revealing how their shape influences electron localization and optical absorption, with potential applications in nanostructure design.

Contribution

It demonstrates how geometry affects electronic states and optical properties, highlighting corner localization effects and the influence of external fields on absorption spectra.

Findings

Electrons are localized near corners regardless of ring shape.

The absorption spectrum shows two peaks related to corner states under magnetic fields.

External electric fields can enable forbidden optical transitions.

Abstract

We investigate theoretically polygonal quantum rings and focus mostly on the triangular geometry where the corner effects are maximal. Such rings can be seen as short core-shell nanowires, a generation of semiconductor heterostructures with multiple applications. We show how the geometry of the sample determines the electronic energy spectrum, and also the localization of electrons, with effects on the optical absorption. In particular, we show that irrespective of the ring shape low-energy electrons are always attracted by corners and are localized in their vicinity. The absorption spectrum in the presence of a magnetic field shows only two peaks within the corner-localized state domain, each associated with different circular polarization. This picture may be changed by an external electric field which allows previously forbidden transitions, and thus enables the number of corners to be determined. We show that polygonal quantum rings allow absorption of waves from distant ranges of the electromagnetic spectrum within one sample.