Possible nanophotonics applications of the $V_N N_B$ defect in hexagonal boron nitride

TL;DR

This paper models the $V_N N_B$ defect in hexagonal boron nitride to explore its potential for nanophotonics, developing new computational methods to analyze its electronic and magnetic properties in various charged states.

Contribution

It introduces novel computational techniques for excited state analysis of the $V_N N_B$ defect, enabling detailed electronic state predictions relevant to nanophotonics.

Findings

Charged defect states show promising properties for nanophotonics.

New methods enable analysis of 45 electronic states of the defect.

Calibration against ab initio methods improves computational robustness.

Abstract

The $V_N N_B$ defect in hexagonal boron nitride (h-BN), comprising a nitrogen vacancy adjacent to a nitrogen-for-boron substitution, is modelled in regard to its possible usefulness in a nanophotonics device. The modelling is done on both a simple model compound and on a 2D periodic representation of the defect, considering its magnetic and spectroscopic properties. The electronic distribution in $V_N N_B$ excited states is very open-shell in nature, and to deal with this two new computational methods are developed: one allows standard density-functional theory (DFT) calculations to be employed to evaluate state energies, the other introduces techniques needed to apply the VASP computational package to these and many other problems involving excited states. Also of general use, results from DFT calculations are then calibrated against those from ab initio methods, seeking robust computational schemes. These innovations allow 45 electronic states of the defect in its neutral, +1 and -1 charged forms to be considered. The charged forms of the defect are predicted to display properties of potential interest to nanophotonics.