Phonon sidebands of color centers in hexagonal boron nitride

Abstract

We report on multicolor excitation experiments with color centers in hexagonal boron nitride at cryogenic temperatures. We demonstrate controllable optical switching between bright and dark states of color centers emitting around 2eV. Resonant, or quasi-resonant excitation also pumps the color center, via a two-photon process, into a dark state, where it becomes trapped. Photoluminescence excitation spectroscopy reveals a defect dependent energy threshold for repumping the color center into the bright state of between 2.2 and 2.6eV. Photoionization and photocharging of the defect is the most plausible explanation for this behaviour, with the negative and neutral charge states of the boron vacancy potential candidates for the bright and dark states,

Stimulated emission depletion spectroscopy of color centers in hexagonal boron nitride

“…For comparison, the magnitude of the detuning from the ZPL is used, because as noted above, PLE uses a laser detuned to higher energies, whereas STED uses a laser detuned to lower energies. As reported previously, [27][28][29] the shape of the PSB corresponds closely to the phonon dispersion relation for 2-dimensional hBN (Fig. 3(a)).…”

Photochromism in a Hexagonal Boron Nitride Single Photon Emitter

“…Further, we characterize the cross-correlations between zero-phonon lines (ZPLs) that exhibit correlated quantum efficiencies with spectrally resolved two-color Hanbury Brown-Twiss (HBT) interferometry. While we have previously used two-color HBT interferometry with photo-stable emitters in hBN under vacuum to verify that the broad emission bands redshifted 166±0.5 meV and 326±0.5 meV from the ZPL are optical oneand two-phonon sidebands respectively, 20 the cross-correlated ZPLs studied in this work have separation energies 20 meV below the known optical phonon modes of hBN 21,22 and localized phonon resonances fail to explain the observed spectrum. 15 Combining irradiation-time dependent measures of quantum efficiency and µPL spectroscopy with two-color HBT interferometry enables this new investigation of the electronic structure of hBN defects.…”

Single‐Photon Emitters in Layered Van der Waals Materials

“…[24] The emission is stable from cryogenic temperature up to room temperature and even high-temperature singlephoton emission up to 800 K was demonstrated. [52] Besides the sharp ZPL, the emission spectrum of the emitters exhibits two prominent sidebands 150 to 200 meV below the ZPL, [41,51,[53][54][55] which originate from optical phonon-assisted emission. [56] The line width of the ZPL increases exponentially with temperature due to the coupling with acoustic phonons [56] (see also Section 2.2).…”

“…Besides the sharp ZPL, the emission spectrum of the emitters exhibits two prominent sidebands 150 to 200 meV below the ZPL, [ 41,51,53–55 ] which originate from optical phonon‐assisted emission. [ 56 ] The line width of the ZPL increases exponentially with temperature due to the coupling with acoustic phonons [ 56 ] (see also Section 2.2).…”