Color centers in hexagonal boron nitride monolayers: A group theory and ab-initio analysis

TL;DR

This paper combines group theory and ab-initio DFT calculations to analyze the electronic and optical properties of color centers in hexagonal boron nitride monolayers, linking them to observed single-photon emission phenomena.

Contribution

It provides a detailed theoretical framework for understanding the electronic structure and emission properties of color centers in h-BN, connecting defect states to experimental single-photon emitters.

Findings

Identification of symmetry and electronic structure of color centers

Calculation of zero-phonon-line emissions matching experiments

Analysis of radiative and non-radiative transition channels

Abstract

We theoretically study physical properties of the most promising color center candidates for the recently observed single-photon emissions in hexagonal boron nitride (h-BN) monolayers. Through our group theory analysis combined with density functional theory (DFT) calculations we provide several pieces of evidence that the electronic properties of the color centers match the characters of the experimentally observed emitters. We calculate the symmetry-adapted multi-electron wavefunctions of the defects using group theory methods and analyze the spin-orbit and spin-spin interactions in detail. We also identify the radiative and non-radiative transition channels for each color center. An advanced ab-initio DFT method is then used to compute energy levels of the color centers and their zero-phonon-line (ZPL) emissions. The computed ZPLs, the profile of excitation and emission dipole polarizations, and the competing relaxation processes are discussed and matched with the observed emission lines. By providing evidence for the relation between single-photon emitters and local defects in h-BN, this work provides the first steps towards harnessing quantum dynamics of these color centers.