Coherence Properties of Electron-Beam-Activated Emitters in Hexagonal Boron Nitride Under Resonant Excitation

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Coherence Properties of Electron-Beam-Activated Emitters in Hexagonal Boron Nitride Under Resonant Excitation

Jake Horder, Simon J.U. White, Angus Gale, Chi Li, Kenji Watanabe, Takashi Taniguchi, Mehran Kianinia, Igor Aharonovich, and Milos Toth

Phys. Rev. Applied 18, 064021 – Published 8 December 2022

Abstract

Two-dimensional (2D) materials are becoming increasingly popular as a platform for studies of quantum phenomena and for the production of prototype quantum technologies. Quantum emitters in 2D materials can host two-level systems that can act as qubits for quantum information processing. Here, we characterize the behavior of position-controlled quantum emitters in hexagonal boron nitride at cryogenic temperatures. Over two dozen sites, we observe an ultranarrow distribution of the zero phonon line at approximately 436 nm, together with strong linearly polarized emission. We employ resonant excitation to characterize the emission lineshape and find spectral diffusion and phonon broadening contribute to linewidths in the range 1–2 GHz. Rabi oscillations are observed at a range of resonant excitation powers, and under 1-µW excitation a coherent superposition is maintained up to 0.90 ns. Our results are promising for future employment of quantum emitters in h-BN for scalable quantum technologies.

Received 27 July 2022
Revised 16 September 2022
Accepted 27 October 2022

DOI:https://doi.org/10.1103/PhysRevApplied.18.064021

Physics Subject Headings (PhySH)

Luminescence Nanophotonics Optical quantum information processing Optoelectronics Point defects Single photon sources

Hexagonal boron nitride

Sample preparation

Condensed Matter, Materials & Applied PhysicsQuantum Information, Science & TechnologyAtomic, Molecular & Optical

Authors & Affiliations

Jake Horder ¹, Simon J.U. White¹, Angus Gale¹, Chi Li¹, Kenji Watanabe ², Takashi Taniguchi ³, Mehran Kianinia ^1,4, Igor Aharonovich^1,4,*, and Milos Toth ^1,4,†

¹School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
²Research Center for Functional Materials, National Institute for Materials Science, Tsukuba 305-0044, Japan
³International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan
⁴ARC Centre of Excellence for Transformative Meta-Optical Systems, University of Technology Sydney, Ultimo, New South Wales 2007, Australia

^*igor.aharonovich@uts.edu.au
^†milos.toth@uts.edu.au

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Issue

Vol. 18, Iss. 6 — December 2022

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Images

Figure 1
Emission characterization. (a) Confocal PL scan of the 12 sites in matrix A (MA), one of three emitter arrays investigated in this work. Scale bar, 1 µm. (b) Normalized PL spectra measured at each site circled in (a). Each plot is vertically offset for clarity. (c) Histogram of ZPL wavelengths extracted from PL spectra across 46 emitter sites at three separate locations on the h-BN flake. The mean wavelength is 435.98 nm ± 0.21 nm. (d) Histogram of emission polarization angles measured from 46 sites, segregated by a polarizability threshold of 0.85. (e) A typical polarization measurement with data in blue and a sinusoidal fit in dashed red.
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Figure 2
Photoluminescence excitation. (a) Ten consecutive PLE scans across the ZPL of an emitter reveal some spectral wandering. Intensity data from each scan is fit with a Lorentzian function and offset vertically for clarity. (b) Average fluorescence intensity from 50 consecutive scans. These data are fit with a Gaussian function, a Lorentzian function, and a Voigt function, from which estimates of the linewidth Γ (FWHM) are extracted. (c) Lifetime measurement obtained using a pulsed laser. The exponential fit yields the excited state lifetime T₁= 2.27 ns ± 0.02 ns. The orange curve is the instrument response function (IRF).
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Figure 3
Linewidth broadening. (a) PLE collected over a range of excitation powers. Each dataset is fit with a Voigt function and plotted with a vertical offset for clarity. (b) The maximum value of each Voigt function in (a) is plotted against the excitation power, and fitted with a power-intensity function to extract the saturation power 3.14 µW. (c) The full width at half maximum of each fitted function in (a) is plotted against the excitation power. (d) PLE collected at a range of temperatures, using an excitation power of 1 µW. Each dataset is fit with a Voigt function and plotted with a vertical offset for clarity. (e) The FWHM of each fitted function in (d) is plotted against the temperature and fit using a cubic function.
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Figure 4
Coherence properties. (a) Second-order correlation measurement collected over a range of excitation powers, and the fitted function demonstrating the presence of Rabi oscillations. Each plot is vertically offset for clarity. Values of $T_{2}^{^{*}}$ are extracted from the fit. (b) The Rabi frequency extracted from the fit in (a) is plotted against the square root of the excitation power, and a linear function is used to fit the data.
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