Ultraviolet quantum emitters in $h$-BN from carbon clusters

TL;DR

This study uses first principles calculations to identify substitutional carbon defects in hexagonal boron nitride as sources of ultraviolet quantum emission, matching experimental signals and offering insights for defect identification.

Contribution

It systematically evaluates various carbon defect configurations in hBN, highlighting the carbon ring defect (6C) as a key UV emitter with properties aligning with experimental observations.

Findings

The 6C defect's zero-phonon line matches the 4.1 eV emission.

6C defect shows strong response to external perturbations.

Comparison reveals key differences in emission mechanisms among defects.

Abstract

Ultraviolet (UV) quantum emitters in hexagonal boron nitride (hBN) have generated considerable interest due to their outstanding optical response. Recent experiments have identified a carbon impurity as a possible source of UV single photon emission. Here, based on the first principles calculations, we systematically evaluate the ability of substitutional carbon defects to develop the UV colour centres in hBN. Of seventeen defect configurations under consideration, we particularly emphasize the carbon ring defect (6C), for which the calculated zero-phonon line (ZPL) agrees well the experimental 4.1-eV emission signal. We also compare the optical properties of 6C with those of other relevant defects, thereby outlining the key differences in the emission mechanism. Our findings provide new insights about the large response from this colour centre to external perturbations and pave the way to a robust identification of the particular carbon substitutional defects by spectroscopic methods.