# The optical selection rules of a graphene quantum dot in external electric fields

## TL;DR

This study theoretically investigates the optical selection rules of a triangular zigzag graphene quantum dot under various in-plane electric fields, revealing symmetry-dependent absorption features and their modulation by external fields.

## Contribution

It identifies how C3 symmetry influences optical selection rules and how electric fields alter absorption spectra in graphene quantum dots, providing insights for device applications.

## Key findings

- Optical selection rules are governed by the C3 symmetry of the quantum dot.
- Electric fields breaking C3 symmetry reduce absorption peak intensities.
- Polarization effects introduce new forbidden transitions.

## Abstract

We study theoretically the single-electron triangular zigzag graphene quantum dot in three typical in-plane electric fields. The far-infrared absorption spectra of the dot are calculated by the tight-binding method and then the optical selection rules are identified by contrast with the corresponding energy spectra. Our result shows that there exist the remarkable optical selection rules due to the C3 symmetry of the dot. When the electric field possesses also the C3 symmetry, there are only two absorption peaks in the absorption spectra. As the C3 symmetry of the system is damaged by the electric fields, both the intensity of the strongest peak and the number of the forbidden transitions decrease gradually. Moreover, the polarization causes the decrease of the peak intensities and even new forbidden transitions. Our findings may be useful for the application of graphene quantum dots to electronic and optoelectronic devices.