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arXiv:2106.03413 · ACS Photonics

Low-Temperature Spectroscopic Investigation of Lead-Vacancy Centers in Diamond Fabricated by High-Pressure and High-Temperature Treatment

Peng Wang, Takashi Taniguchi, Yoshiyuki Miyamoto, Mutsuko Hatano, Takayuki Iwasaki

Published Sep 15, 2021• 32 citations
arXivHTMLPDF

Abstract

We report the optical observation of lead-vacancy (PbV) centers in diamond fabricated by Pb ion implantation and subsequent high-temperature annealing (2100 °C) under high pressure (7.7 GPa). Their optical properties were characterized by photoluminescence at varying temperatures down to 5.7 K. We observed intense emission peaks at 550 and 554 nm, with a large splitting of approximately 3900 GHz. The two lines are thought to correspond to the zero phonon line (ZPL) of PbV centers with split ground and excited states. A cubic trend of the ZPL width was observed while varying the temperature. We performed polarization measurements of the two lines in a single PbV center, showing nearly orthogonal dipole polarizations. These optical measurements strongly indicate that the PbV center possesses D 3 d symmetry in the diamond lattice. The observed large ground state splitting significantly suppresses the phonon-mediated transition, which causes decoherence of the electron spin state of the group IV color centers in diamond, leading to the expectation of a long spin coherence time at a temperature ∼9 K.

DOI
10.1021/acsphotonics.1c00840

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We report the optical observation of lead-vacancy (PbV) centers in diamond fabricated by Pb ion implantation and subsequent high-temperature annealing (2100 °C) under high pressure (7.7 GPa). Their optical properties were characterized by photoluminescence at varying temperatures down to 5.7 K. We observed intense emission peaks at 550 and 554 nm, with a large splitting of approximately 3900 GHz. The two lines are thought to correspond to the zero phonon line (ZPL) of PbV centers with split ground and excited states. A cubic trend of the ZPL width was observed while varying the temperature. We performed polarization measurements of the two lines in a single PbV center, showing nearly orthogonal dipole polarizations. These optical measurements strongly indicate that the PbV center possesses D 3 d symmetry in the diamond lattice. The observed large ground state splitting significantly suppresses the phonon-mediated transition, which causes decoherence of the electron spin state of the group IV color centers in diamond, leading to the expectation of a long spin coherence time at a temperature ∼9 K.
We report on quantum emission from Pb-related color centers in diamond following ion implantation and high-temperature vacuum annealing. First-principles calculations predict a negatively charged Pb-vacancy (PbV) center in a split-vacancy configuration, with a zero-phonon transition around 2.4 eV. Cryogenic photoluminescence measurements performed on emitters in nanofabricated pillars reveal several transitions, including a prominent doublet near 520 nm. The splitting of this doublet, 5.7 THz, exceeds that reported for other group-IV centers. These observations are consistent with the PbV center, which is expected to have a combination of narrow optical transitions and stable spin states, making it a promising system for quantum network nodes.
Transform-limited photon emission from quantum emitters is essential for high-fidelity entanglement generation. In this Letter, we report the coherent optical property of a single negatively charged lead-vacancy (PbV) center in diamond. Photoluminescence excitation measurements reveal stable fluorescence with a linewidth of 39 MHz at 6 K, close to the transform limit estimated from the lifetime measurement. We observe 4 orders of magnitude different linewidths of the two zero-phonon lines, and find that the phonon-induced relaxation in the ground state contributes to this huge difference in the linewidth. Because of the suppressed phonon absorption in the PbV center, we observe nearly transform-limited photon emission up to 16 K, demonstrating its high temperature robustness compared to other color centers in diamond.
Abstract We report on the creation and characterization of Pb-related color centers in diamond upon ion implantation and subsequent thermal annealing. Their optical emission in the photoluminescence (PL) regime consists of an articulated spectrum with intense emission peaks at 552.1 and 556.8 nm, accompanied by a set of additional lines in the 535–700 nm range. The attribution of the PL emission to stable Pb-based defects is corroborated by the correlation of its intensity with the implantation fluence of Pb ions. PL measurements performed as a function of sample temperature (in the 143–300 K range) and under different excitation wavelengths (i.e., 532, 514, 405 nm) suggest that the complex spectral features observed in Pb-implanted diamond might be related to a variety of different defects and/or charge states. The emission of the 552.1 and 556.8 nm lines is reported at the single-photon emitter level, demonstrating that they originate from the same individual defect. This work follows from previous reports on optically active centers in diamond based on group-IV impurities, such as Si, Ge, and Sn. In perspective, a comprehensive study of this set of defect complexes could bring significant insight on the common features involved in their formation and opto-physical properties, thus offering a basis for the development of a new generation of quantum-optical devices.
A negatively charged lead-vacancy (PbV-) center in diamond is a novel quantum system which can be operated at a high temperature above 4 K owing to its large ground state splitting. To unlock the quantum properties of the PbV- center, the enhancement of the fluorescence intensity is a key issue. Here, we demonstrate enhanced emission from PbV- centers by a factor of approximately 10 using solid immersion lenses (SILs) fabricated on rough diamond surface caused by high-temperature anneal over 2000°C. Resonant excitation reveals the narrow emission close to the transform-limited linewidth. Furthermore, we demonstrate two-photon interference using one single PbV- center in an SIL. This enhanced emission and indistinguishability will lead to further development of the PbV- center towards quantum network node applications.
Abstract Lead‐vacancy (PbV) centers in diamond with a large ground state splitting are expected to be a building block of quantum network nodes. Due to the heaviness of the Pb atom, it is challenging to fabricate high‐quality PbV centers with a narrow inhomogeneous distribution and stable charge state. In this study, for the formation of the PbV centers, high‐temperature anneal up to 2300 °C is performed after Pb ion implantation. At a lower temperature of 1800 °C, the PbV centers show a large inhomogeneous distribution and spectral diffusion, while higher temperatures of 2200–2300 °C leads to narrow inhomogeneous distributions with standard deviations of ≈5 GHz. The charge state transition of the PbV centers formed at 2200 °C occurs by capturing photo‐carriers generated from surrounding defects under 532 nm laser irradiation. Finally, multiple stable PbV centers with nearly identical photon frequencies are obtained, which is essential for applications in quantum information processing.
A lead-vacancy (PbV) center in diamond exhibits coherent emission above the liquid helium temperature, making it highly attractive for quantum network applications. Here, we report the magneto-optical and spin properties of PbV centers in diamond. We record a spin lifetime of 12 ms at 7.5 K under large off-axis magnetic field. Furthermore, we observe formation of the coherent dark state by coherent population trapping and estimate a spin dephasing time of 177 ns at 6.5 K. This work demonstrates the outstanding thermal robustness of the PbV spin compared to other group-IV centers above 4 K.