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Register a new userHigh-contrast plasmonic-enhanced shallow spin defects in hexagonal boron nitride for quantum sensing
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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.
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Optically active spin defects in wide-bandgap materials have many potential applications in quantum information and quantum sensing. Spin defects in two-dimensional layered van der Waals materials are just emerging to be investigated. Here we demonstrate that optically-addressable spin ensembles in hexagonal boron nitride (hBN) can be generated by femtosecond laser irradiation. We observe optically detected magnetic resonance (ODMR) of hBN spin defects created by laser irradiation. We show that the creation of spin defects in hBN is strongly affected by the pulse energy of the femtosecond laser. When the laser pulse number is less than a few thousand, the pulse number only affects the density of defects but not the type of defects. With proper laser parameters, spin defects can be generated with a high probability of success. Our work provides a convenient way to create spin defects in hBN by femtosecond laser writing, which shows promising prospects for quantum technologies.
Two-dimensional hexagonal boron nitride offers intriguing opportunities for advanced studies of light-matter interaction at the nanoscale, specifically for realizations in quantum nanophotonics. Here, we demonstrate the engineering of optically-addressable spin defects based on the negatively-charged boron vacancy center. We show that these centers can be created in exfoliated hexagonal boron nitride using a variety of focused ion beams (nitrogen, xenon and argon), with nanoscale precision. Using a combination of laser and resonant microwave excitation, we carry out optically detected magnetic resonance spectroscopy measurements, which reveal a zero-field ground state splitting for the defect of ~3.46 GHz. We also perform photoluminescence excitation spectroscopy and temperature dependent photoluminescence measurements to elucidate the photophysical properties of the center. Our results are important for advanced quantum and nanophotonics realizations involving manipulation and readout of spin defects in hexagonal boron nitride.
Optically addressable spin defects in wide-bandage semiconductors as promising systems for quantum information and sensing applications have attracted more and more attention recently. Spin defects in two-dimensional materials are supposed to have unique superiority in quantum sensing since their atomatic thickness. Here, we demonstrate that the negatively boron charged vacancy (V$ _text{B}^{-} $) with good spin properties in hexagonal boron nitride can be generated by ion implantation. We carry out optically detected magnetic resonance measurements at room temperature to characterize the spin properties of V$ _text{B}^{-} $ defects, showing zero-filed splitting of $ sim $ 3.47 GHz. We compare the photoluminescence intensity and spin properties of V$ _text{B}^{-} $ defects generated by different implantation parameters, such as fluence, energy and ion species. With proper parameters, we can create V$ _text{B}^{-} $ defects successfully with high probability. Our results provide a simple and practicable method to create spin defects in hBN, which is of great significance for integrated hBN-based devices.
Two-dimensional hexagonal boron nitride (hBN) has attracted large attentions as platforms for realizations for integrated nanophotonics and collective effort has been focused on the spin defect centers. Here, the temperature dependence of the resonance spectrum in the range of 5-600 K is investigated. The zero-field splitting (ZFS) parameter D is found to decrease monotonicly with increasing temperature and can be described by Varshni empirical equation perfectly, while E almost does not change. We systematically study the differences among different hBN nanopowders and provide an evidence of edge effects on ODMR of VB- defects. Considering the proportional relation between D and reciprocal of lattice volume, the thermal expansion might be the dominant reason for energy-level shifts. We also demonstrate that the VB- defects still exist stably at least at 600 K. Moreover, we propose a scheme for detecting laser intensity using the VB- defects in hBN nanopowders, which is based on the obvious dependence of its D value on laser intensity. Our results are helpful to gain insight into the spin properties of VB- and for the realizations of miniaturized, integrated thermal sensor.
We propose an electromechanical scheme where the electronic degrees of freedom of boron vacancy color centers hosted by a hexagonal boron nitride nanoribbon are coupled for quantum information processing. The mutual coupling of color centers is provided via their coupling to the mechanical motion of the ribbon, which in turn stems from the local strain. The coupling strengths are computed by performing ab-initio calculations. The density functional theory (DFT) results for boron vacancy centers on boron nitride monolayers reveal a huge strain susceptibility. In our analysis, we take into account the effect of all flexural modes and show that despite the thermal noise introduced through the vibrations one can achieve steady-state entanglement between two and more number of qubits that survives even at room temperature. Moreover, the entanglement is robust against mis-positioning of the color centers. The effective coupling of color centers is engineered by positioning them in the proper positions. Hence, one is able to tailor stationary graph states. Furthermore, we study the quantum simulation of the Dicke-Ising model and show that the phonon superradiance phase transition occurs even for a finite number of color centers. Given the steady-state nature of the proposed scheme and accessibility of the electronic states through optical fields, our work paves the way for the realization of steady-state quantum information processing with color centers in hexagonal boron nitride membranes.
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