Optical Signatures of Quantum Emitters in Suspended Hexagonal Boron Nitride

TL;DR

This study investigates the optical properties of quantum emitters in suspended hexagonal boron nitride, revealing stable single-photon sources and insights into their electronic structure, which are crucial for quantum technology applications.

Contribution

The paper demonstrates the creation and detailed optical characterization of stable, suspended h-BN quantum emitters, providing new insights into their spectral and polarization properties.

Findings

Emitters are bright and stable over months in ambient conditions.

Spectral analysis shows similarities in vibronic coupling across different wavelengths.

Polarization patterns suggest multiple classes of emitters and defect models.

Abstract

Hexagonal boron nitride (h-BN) is a tantalizing material for solid-state quantum engineering. Analogously to three-dimensional wide-bandgap semiconductors like diamond, h-BN hosts isolated defects exhibiting visible fluorescence, and the ability to position such quantum emitters within a two-dimensional material promises breakthrough advances in quantum sensing, photonics, and other quantum technologies. Critical to such applications, however, is an understanding of the physics underlying h-BN's quantum emission. We report the creation and characterization of visible single-photon sources in suspended, single-crystal, h-BN films. The emitters are bright and stable over timescales of several months in ambient conditions. With substrate interactions eliminated, we study the spectral, temporal, and spatial characteristics of the defects' optical emission, which offer several clues about their electronic and chemical structure. Analysis of the defects' spectra reveals similarities in vibronic coupling despite widely-varying fluorescence wavelengths, and a statistical analysis of their polarized emission patterns indicates a correlation between the optical dipole orientations of some defects and the primitive crystallographic axes of the single-crystal h-BN film. These measurements constrain possible defect models, and, moreover, suggest that several classes of emitters can exist simultaneously in free-standing h-BN, whether they be different defects, different charge states of the same defect, or the result of strong local perturbations.