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Register a new userAll-optical dc nanotesla magnetometry using silicon vacancy fine structure in isotopically purified silicon carbide
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We uncover the fine structure of a silicon vacancy in isotopically purified silicon carbide (4H-$^{28}$SiC) and find extra terms in the spin Hamiltonian, originated from the trigonal pyramidal symmetry of this spin-3/2 color center. These terms give rise to additional spin transitions, which are otherwise forbidden, and lead to a level anticrossing in an external magnetic field. We observe a sharp variation of the photoluminescence intensity in the vicinity of this level anticrossing, which can be used for a purely all-optical sensing of the magnetic field. We achieve dc magnetic field sensitivity of 87 nT Hz$^{-1/2}$ within a volume of $3 times 10^{-7}$ mm$^{3}$ at room temperature and demonstrate that this contactless method is robust at high temperatures up to at least 500 K. As our approach does not require application of radiofrequency fields, it is scalable to much larger volumes. For an optimized light-trapping waveguide of 3 mm$^{3}$ the projection noise limit is below 100 fT Hz$^{-1/2}$.
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Silicon Carbide is a promising host material for spin defect based quantum sensors owing to its commercial availability and established techniques for electrical and optical microfabricated device integration. The negatively charged silicon vacancy is one of the leading spin defects studied in silicon carbide owing to its near telecom photoemission, high spin number, and nearly temperature independent ground state zero field splitting. We report the realization of nanoTesla shot-noise limited ensemble magnetometry based on optically detected magnetic resonance with the silicon vacancy in 4H silicon carbide. By coarsely optimizing the anneal parameters and minimizing power broadening, we achieved a sensitivity of 3.5 nT/$sqrt{Hz}$. This was accomplished without utilizing complex photonic engineering, control protocols, or applying excitation powers greater than a Watt. This work demonstrates that the silicon vacancy in silicon carbide provides a low-cost and simple approach to quantum sensing of magnetic fields.
The silicon-vacancy centre (SiV) in diamond has interesting vibronic features. We demonstrate that the zero phonon line position can be used to reliably identify the silicon isotope present in a single centre. This is of interest for quantum information applications since only the silicon 29 isotope has nuclear spin. In addition, we demonstrate that the 64 meV line is due to a local vibrational mode of the silicon atom. The presence of a local mode suggests a plausible origin of the isotopic shift of the zero phonon line.
We discovered uniaxial oriented centers in silicon carbide having unusual performance. Here we demonstrate that the family of silicon-vacancy related centers with $S= 3/2$ in rhombic 15R-SiC crystalline matrix possess unique characteristics such as ODMR contrast and optical spin alignment existing at temperatures up to 250$^circ$C. Thus the concept of optically addressable silicon vacancy related centers with half integer ground spin state is extended to the wide class of SiC rhombic polytypes. The structure of these centers, which is a fundamental problem for quantum applications, has been established using high frequency ENDOR. It has been shown that a family of siliconvacancy related centers is a negatively charged silicon vacancy in the paramagnetic state with the spin $S= 3/2$, V$_textrm{Si}^-$, perturbed by neutral carbon vacancy in non-paramagnetic state, V$_textrm{C}^0$, having no covalent bond with the silicon vacancy and located adjacently to the silicon vacancy on the c crystal axis.
We report a giant thermal shift of $2.1 ,$MHz/K related to the excited-state zero-field splitting in the silicon vacancy centers in 4H silicon carbide. It is obtained from the indirect observation of the optically detected magnetic resonance in the excited state using the ground state as an ancilla. Alternatively, relative variations of the zero-field splitting for small temperature differences can be detected without application of radiofrequency fields, by simply monitoring the photoluminescence intensity in the vicinity of the level anticrossing. This effect results in an all-optical thermometry technique with temperature sensitivity of $100 ,$mK/Hz$^{1/2}$ for a detection volume of approximately $10^{-6} ,$mm$^{3}$. In contrast, the zero-field splitting in the ground state does not reveal detectable temperature shift. Using these properties, an integrated magnetic field and temperature sensor can be implemented on the same center.
Defects in silicon carbide have been explored as promising spin systems in quantum technologies. However, for practical quantum metrology and quantum communication, it is critical to achieve the on-demand shallow spin-defect generation. In this work, we present the generation and characterization of shallow silicon vacancies in silicon carbide by using different implanted ions and annealing conditions. The conversion efficiency of silicon vacancy of helium ions is shown to be higher than that by carbon and hydrogen ions in a wide implanted fluence range. Furthermore, after optimizing annealing conditions, the conversion efficiency can be increased more than 2 times. Due to the high density of the generated ensemble defects, the sensitivity to sense a static magnetic field can be research as high as , which is about 15 times higher than previous results. By carefully optimizing implanted conditions, we further show that a single silicon vacancy array can be generated with about 80 % conversion efficiency, which reaches the highest conversion yield in solid state systems. The results pave the way for using on-demand generated shallow silicon vacancy for quantum information processing and quantum photonics.
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