title: Optical Signatures of Quantum Emitters in Suspended Hexagonal Boron Nitride.
abstract: Hexagonal boron nitride (h-BN) is rapidly emerging as an attractive material for solid-state quantum engineering. Analogously to three-dimensional wide-band-gap semiconductors such as diamond, h-BN hosts isolated defects exhibiting visible fluorescence at room temperature, 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 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. With substrate interactions eliminated, we study the spectral, temporal, and spatial characteristics of the defects' optical emission. Theoretical analysis of the defects' spectra reveals similarities in vibronic coupling to h-BN phonon modes despite widely varying fluorescence wavelengths, and a statistical analysis of the polarized emission from many emitters throughout the same single-crystal flake uncovers a weak correlation between the optical dipole orientations of some defects and h-BN's primitive crystallographic axes, despite a clear misalignment for other dipoles. These measurements constrain possible defect models and, moreover, suggest that several classes of emitters can exist simultaneously throughout free-standing h-BN, whether they be different defects, different charge states of the same defect, or the result of strong local perturbations.
authors.forename: Annemarie L
authors.identifier: 0000-0003-3026-7737
authors.initials: AL
authors.lastname: Exarhos
authors.forename: David A
authors.identifier: 0000-0003-1965-690X
authors.initials: DA
authors.lastname: Hopper
authors.forename: Richard R
authors.initials: RR
authors.lastname: Grote
authors.affiliation: Center for Physical Sciences and Technology , Vilnius LT-10257, Lithuania.|Department of Physics, Kaunas University of Technology , Kaunas LT-51368, Lithuania.
authors.forename: Audrius
authors.identifier: 0000-0002-4228-6612
authors.initials: A
authors.lastname: Alkauskas
authors.forename: Lee C
authors.identifier: 0000-0001-8729-1530
authors.initials: LC
authors.lastname: Bassett
keywords: Huang−Rhys factor; dipole−lattice coupling; fluorescent defect; hexagonal boron nitride; single crystal; single-photon source