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1. Wide field imaging of van der Waals ferromagnet Fe3GeTe2 by spin defects in hexagonal boron nitride

   https://doi.org/10.1038/s41467-022-33016-2  

   Huang, Mengqi; Zhou, Jingcheng; Chen, Di; Lu, Hanyi; McLaughlin, Nathan J.; Li, Senlei; Alghamdi, Mohammed; Djugba, Dziga; Shi, Jing; Wang, Hailong; et al (September 2022, Nature Communications)

   Abstract Emergent color centers with accessible spins hosted by van der Waals materials have attracted substantial interest in recent years due to their significant potential for implementing transformative quantum sensing technologies. Hexagonal boron nitride (hBN) is naturally relevant in this context due to its remarkable ease of integration into devices consisting of low-dimensional materials. Taking advantage of boron vacancy spin defects in hBN, we report nanoscale quantum imaging of low-dimensional ferromagnetism sustained in Fe₃GeTe₂/hBN van der Waals heterostructures. Exploiting spin relaxometry methods, we have further observed spatially varying magnetic fluctuations in the exfoliated Fe₃GeTe₂flake, whose magnitude reaches a peak value around the Curie temperature. Our results demonstrate the capability of spin defects in hBN of investigating local magnetic properties of layered materials in an accessible and precise way, which can be extended readily to a broad range of miniaturized van der Waals heterostructure systems. 

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2. Excited-state spin-resonance spectroscopy of V$${}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ defect centers in hexagonal boron nitride

   https://doi.org/10.1038/s41467-022-30772-z  

   Mathur, Nikhil; Mukherjee, Arunabh; Gao, Xingyu; Luo, Jialun; McCullian, Brendan A.; Li, Tongcang; Vamivakas, A. Nick; Fuchs, Gregory D. (June 2022, Nature Communications)

   Abstract The recently discovered spin-active boron vacancy (V$${}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ ${}_B^{-}$) defect center in hexagonal boron nitride (hBN) has high contrast optically-detected magnetic resonance (ODMR) at room-temperature, with a spin-triplet ground-state that shows promise as a quantum sensor. Here we report temperature-dependent ODMR spectroscopy to probe spin within the orbital excited-state. Our experiments determine the excited-state spin Hamiltonian, including a room-temperature zero-field splitting of 2.1 GHz and a g-factor similar to that of the ground-state. We confirm that the resonance is associated with spin rotation in the excited-state using pulsed ODMR measurements, and we observe Zeeman-mediated level anti-crossings in both the orbital ground- and excited-state. Our observation of a single set of excited-state spin-triplet resonance from 10 to 300 K is suggestive of symmetry-lowering of the defect system fromD_3htoC_2v. Additionally, the excited-state ODMR has strong temperature dependence of both contrast and transverse anisotropy splitting, enabling promising avenues for quantum sensing. 

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3. Single nuclear spin detection and control in a van der Waals material

   https://doi.org/10.1038/s41586-025-09258-7  

   Gao, Xingyu; Vaidya, Sumukh; Li, Kejun; Ge, Zhun; Dikshit, Saakshi; Zhang, Shimin; Ju, Peng; Shen, Kunhong; Jin, Yuanbin; Ping, Yuan; et al (July 2025, Nature)

   Abstract Optically active spin defects in solids^1,2are leading candidates for quantum sensing^3,4and quantum networking^5,6. Recently, single spin defects were discovered in hexagonal boron nitride (hBN)^7–11, a layered van der Waals (vdW) material. Owing to its two-dimensional structure, hBN allows spin defects to be positioned closer to target samples than in three-dimensional crystals, making it ideal for atomic-scale quantum sensing¹², including nuclear magnetic resonance (NMR) of single molecules. However, the chemical structures of these defects^7–11remain unknown and detecting a single nuclear spin with a hBN spin defect has been elusive. Here we report the creation of single spin defects in hBN using¹³C ion implantation and the identification of three distinct defect types based on hyperfine interactions. We observed bothS = 1/2 andS = 1 spin states within a single hBN spin defect. We demonstrated atomic-scale NMR and coherent control of individual nuclear spins in a vdW material, with a π-gate fidelity up to 99.75% at room temperature. By comparing experimental results with density functional theory (DFT) calculations, we propose chemical structures for these spin defects. Our work advances the understanding of single spin defects in hBN and provides a pathway to enhance quantum sensing using hBN spin defects with nuclear spins as quantum memories. 

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4. Isotope engineering for spin defects in van der Waals materials

   https://doi.org/10.1038/s41467-023-44494-3  

   Gong, Ruotian; Du, Xinyi; Janzen, Eli; Liu, Vincent; Liu, Zhongyuan; He, Guanghui; Ye, Bingtian; Li, Tongcang; Yao, Norman Y; Edgar, James H; et al (December 2024, Nature Communications)

   Abstract Spin defects in van der Waals materials offer a promising platform for advancing quantum technologies. Here, we propose and demonstrate a powerful technique based on isotope engineering of host materials to significantly enhance the coherence properties of embedded spin defects. Focusing on the recently-discovered negatively charged boron vacancy center ($${{{{{{{{\rm{V}}}}}}}}}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ $V_B^{-}$) in hexagonal boron nitride (hBN), we grow isotopically purified h¹⁰B¹⁵N crystals. Compared to$${{{{{{{{\rm{V}}}}}}}}}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ $V_B^{-}$in hBN with the natural distribution of isotopes, we observe substantially narrower and less crowded$${{{{{{{{\rm{V}}}}}}}}}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ $V_B^{-}$spin transitions as well as extended coherence timeT₂and relaxation timeT₁. For quantum sensing,$${{{{{{{{\rm{V}}}}}}}}}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ $V_B^{-}$centers in our h¹⁰B¹⁵N samples exhibit a factor of 4 (2) enhancement in DC (AC) magnetic field sensitivity. For additional quantum resources, the individual addressability of the$${{{{{{{{\rm{V}}}}}}}}}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ $V_B^{-}$hyperfine levels enables the dynamical polarization and coherent control of the three nearest-neighbor¹⁵N nuclear spins. Our results demonstrate the power of isotope engineering for enhancing the properties of quantum spin defects in hBN, and can be readily extended to improving spin qubits in a broad family of van der Waals materials. 

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5. Sensing spin wave excitations by spin defects in few-layer-thick hexagonal boron nitride

   https://doi.org/10.1126/sciadv.adk8495  

   Zhou, Jingcheng; Lu, Hanyi; Chen, Di; Huang, Mengqi; Yan, Gerald Q; Al-matouq, Faris; Chang, Jiu; Djugba, Dziga; Jiang, Zhigang; Wang, Hailong; et al (May 2024, Science Advances)

   Optically active spin defects in wide bandgap semiconductors serve as a local sensor of multiple degrees of freedom in a variety of “hard” and “soft” condensed matter systems. Taking advantage of the recent progress on quantum sensing using van der Waals (vdW) quantum materials, here we report direct measurements of spin waves excited in magnetic insulator Y₃Fe₅O₁₂(YIG) by boron vacancy $V_{\mathrm{B}}^{-}$spin defects contained in few-layer-thick hexagonal boron nitride nanoflakes. We show that the ferromagnetic resonance and parametric spin excitations can be effectively detected by $V_{\mathrm{B}}^{-}$spin defects under various experimental conditions through optically detected magnetic resonance measurements. The off-resonant dipole interaction between YIG magnons and $V_{\mathrm{B}}^{-}$spin defects is mediated by multi-magnon scattering processes, which may find relevant applications in a range of emerging quantum sensing, computing, and metrology technologies. Our results also highlight the opportunities offered by quantum spin defects in layered two-dimensional vdW materials for investigating local spin dynamic behaviors in magnetic solid-state matters. 

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