More Like this

1. Coherent dynamics of strongly interacting electronic spin defects in hexagonal boron nitride

   https://doi.org/10.1038/s41467-023-39115-y  

   Gong, Ruotian ; He, Guanghui ; Gao, Xingyu ; Ju, Peng ; Liu, Zhongyuan ; Ye, Bingtian ; Henriksen, Erik A. ; Li, Tongcang ; Zu, Chong ( June 2023 , Nature Communications)

   Optically active spin defects in van der Waals materials are promising platforms for modern quantum technologies. Here we investigate the coherent dynamics of strongly interacting ensembles of negatively charged boron-vacancy ($${{{{{{{{\rm{V}}}}}}}}}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$$V_B^{-}$) centers in hexagonal boron nitride (hBN) with varying defect density. By employing advanced dynamical decoupling sequences to selectively isolate different dephasing sources, we observe more than 5-fold improvement in the measured coherence times across all hBN samples. Crucially, we identify that the many-body interaction within the$${{{{{{{{\rm{V}}}}}}}}}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$$V_B^{-}$ensemble plays a substantial role in the coherent dynamics, which is then used to directly estimate the concentration of$${{{{{{{{\rm{V}}}}}}}}}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$$V_B^{-}$. We find that at high ion implantation dosage, only a small portion of the created boron vacancy defects are in the desired negatively charged state. Finally, we investigate the spin response of$${{{{{{{{\rm{V}}}}}}}}}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$$V_B^{-}$to the local charged defects induced electric field signals, and estimate its ground state transverse electric field susceptibility. Our results provide new insights on the spin and charge properties of$${{{{{{{{\rm{V}}}}}}}}}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$$V_B^{-}$, which are important for future use of defects in hBN as quantum sensors and simulators.

    

   more » « less
2. High-Contrast Plasmonic-Enhanced Shallow Spin Defects in Hexagonal Boron Nitride for Quantum Sensing

   https://doi.org/10.1021/acs.nanolett.1c02495  

   Gao, Xingyu ; Jiang, Boyang ; Llacsahuanga Allcca, Andres E. ; Shen, Kunhong ; Sadi, Mohammad A. ; Solanki, Abhishek B. ; Ju, Peng ; Xu, Zhujing ; Upadhyaya, Pramey ; Chen, Yong P. ; et al ( September 2021 , Nano Letters)

   null (Ed.)

   The recently discovered spin defects in hexagonal boron nitride (hBN), a layered van der Waals material, have great potential in quantum sensing. However, the photoluminescence and the contrast of the optically detected magnetic resonance (ODMR) of hBN spin defects are relatively low so far, which limits their sensitivity. Here we report a record-high ODMR contrast of 46% at room temperature and simultaneous enhancement of the photoluminescence of hBN spin defects by up to 17-fold by the surface plasmon of a gold film microwave waveguide. Our results are obtained with shallow boron vacancy spin defects in hBN nanosheets created by low-energy He+ ion implantation and a gold film microwave waveguide fabricated by photolithography. We also explore the effects of microwave and laser powers on the ODMR and improve the sensitivity of hBN spin defects for magnetic field detection. Our results support the promising potential of hBN spin defects for nanoscale quantum sensing. 

   more » « less
3. 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)

   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.

    

   more » « less
4. Investigation of photon emitters in Ce-implanted hexagonal boron nitride

   https://doi.org/10.1364/OME.434083  

   López-Morales, Gabriel I. ; Li, Mingxing ; Hampel, Alexander ; Satapathy, Sitakanta ; Proscia, Nicholas V. ; Jayakumar, Harishankar ; Lozovoi, Artur ; Pagliero, Daniela ; Lopez, Gustavo E. ; Menon, Vinod M. ; et al ( September 2021 , Optical Materials Express)

   Color centers in hexagonal boron nitride (hBN) are presently attracting broad interest as a novel platform for nanoscale sensing and quantum information processing. Unfortunately, their atomic structures remain largely elusive and only a small percentage of the emitters studied thus far have the properties required to serve as optically addressable spin qubits. Here, we use confocal fluorescence microscopy at variable temperatures to study a new class of point defects produced via cerium ion implantation in thin hBN flakes. We find that, to a significant fraction, emitters show bright room-temperature emission, and good optical stability suggesting the formation of Ce-based point defects. Using density functional theory (DFT) we calculate the emission properties of candidate emitters, and single out the CeV_Bcenter—formed by an interlayer Ce atom adjacent to a boron vacancy—as one possible microscopic model. Our results suggest an intriguing route to defect engineering that simultaneously exploits the singular properties of rare-earth ions and the versatility of two-dimensional material hosts.

    

   more » « less
5. 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)

   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.

    

   more » « less