Dangling Bonds in Hexagonal Boron Nitride as Single-Photon Emitters.

Area of Science:

• Materials Science
• Quantum Optics
• Solid-State Physics

Background:

• Hexagonal boron nitride (hBN) is known to host color centers exhibiting single-photon emission.
• The precise microscopic origin of these single-photon emitters in hBN remains unidentified.

Purpose of the Study:

• To propose and investigate the microscopic origin of single-photon emission in hexagonal boron nitride.
• To elucidate the electronic and optical properties of potential color centers.

Main Methods:

• Theoretical investigation using first-principles calculations.
• Modeling of electronic transitions within the band gap of hexagonal boron nitride.

Main Results:

• Boron dangling bonds are identified as the likely source of single-photon emission around 2 eV.
• A specific optical transition involving a doubly occupied boron dangling bond predicts a zero-phonon line at 2.06 eV and a Huang-Rhys factor of 2.3.
• Calculations indicate linear polarization with aligned dipoles for direct excitation, and dipole misalignment for indirect excitation via the conduction band.

Conclusions:

• The proposed boron dangling bond model successfully explains the experimentally observed single-photon emission properties, including polarization and energy.
• The model predicts a singlet ground state and a metastable triplet state, consistent with experimental observations.
• This work provides a fundamental understanding of color centers in hexagonal boron nitride, crucial for quantum applications.