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    Magnetic field and temperature sensing with atomic-scale spin defects in silicon carbide

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    Quantum systems can provide outstanding performance in various sensing applications, ranging from bioscience to nanotechnology. Atomic-scale defects in silicon carbide are very attractive in this respect because of the technological advantages of this material and favorable optical and radio frequency spectral ranges to control these defects. We identified several, separately addressable spin-3/2 centers in the same silicon carbide crystal, which are immune to nonaxial strain fluctuations. Some of them are characterized by nearly temperature independent axial crystal fields, making these centers very attractive for vector magnetometry. Contrarily, the zero-field splitting of another center exhibits a giant thermal shift of -1.1 MHz/K at room temperature, which can be used for thermometry applications. We also discuss a synchronized composite clock exploiting spin centers with different thermal response.Comment: 8 pages, 7 figure

    All-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^{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‚ąí1/2^{-1/2} within a volume of 3√ó10‚ąí73 \times 10^{-7} mm3^{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 mm3^{3} the projection noise limit is below 100 fT Hz‚ąí1/2^{-1/2}.Comment: 12 pages, 6 figures; additional experimental data and an extended theoretical analysis are added in the second versio
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