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Register a new userTemperature dependence of the $^{13}$C hyperfine structure of the negatively-charged nitrogen-vacancy center in diamond
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The nitrogen-vacancy (NV) center is a well utilized system for quantum technology, in particular quantum sensing and microscopy. Fully employing the NV centers capabilities for metrology requires a strong understanding of the behavior of the NV center with respect to changing temperature. Here, we probe the NV electronic spin density as the surrounding crystal temperature changes from 10 K to 700 K by examining its $^{13}$C hyperfine interactions. These results are corroborated with textit{ab initio} calculations and demonstrate that the change in hyperfine interaction is small and dominated by a change in the hybridization of the orbitals constituting the spin density. Thus indicating that the defect and local crystal geometry is returning towards an undistorted structure at higher temperature.
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The negatively-charged silicon-vacancy (SiV$^-$) center in diamond is a promising single photon source for quantum communications and information processing. However, the centers implementation in such quantum technologies is hindered by contention surrounding its fundamental properties. Here we present optical polarization measurements of single centers in bulk diamond that resolve this state of contention and establish that the center has a $langle111rangle$ aligned split-vacancy structure with $D_{3d}$ symmetry. Furthermore, we identify an additional electronic level and evidence for the presence of dynamic Jahn-Teller effects in the centers 738 nm optical resonance.
Deep defects in wide band gap semiconductors have emerged as leading qubit candidates for realizing quantum sensing and information applications. Due to the spatial localization of the defect states, these deep defects can be considered as artificial atoms/molecules in a solid state matrix. Here we show that unlike single-particle treatments, the multiconfigurational quantum chemistry methods, traditionally reserved for atoms/molecules, accurately describe the many-body characteristics of the electronic states of these defect centers and correctly predict properties that single-particle treatments fail to obtain. We choose the negatively charged nitrogen-vacancy (NV$^-$) center in diamond as the prototype defect to study with these techniques due to its importance for quantum information applications and because its properties are well-known, which makes it an ideal benchmark system. By properly accounting for electron correlations and including spin-orbit coupling and dipolar spin-spin coupling in the quantum chemistry calculations, for the NV$^-$ center in diamond clusters, we are able to: (i) show the correct splitting of the ground (first-excited) triplet state into two levels (four levels), (ii) calculate zero-field splitting values of the ground and excited triplet states, in good agreement with experiment, and (iii) calculate the energy differences between ground and exited spin-triplet and spin-singlet states, as well as their ordering, which are also found to be in good agreement with recent experimental data. The numerical procedure we have developed is general and it can screen other color centers whose properties are not well known but promising for applications.
The nitrogen-vacancy (NV) center in diamond is a widely-utilized system due to its useful quantum properties. Almost all research focuses on the negative charge state (NV$^-$) and comparatively little is understood about the neutral charge state (NV$^0$). This is surprising as the charge state often fluctuates between NV$^0$, and NV$^-$, during measurements. There are potentially under utilized technical applications that could take advantage of NV$^0$, either by improving the performance of NV$^-$, or utilizing NV$^0$, directly. However, the fine-structure of NV$^0$, has not been observed. Here, we rectify this lack of knowledge by performing magnetic circular dichroism (MCD) measurements that quantitatively determine the fine-structure of NV$^0$. The observed behavior is accurately described by spin-Hamiltonians in the ground and excited states with the ground state yielding a spin-orbit coupling of $lambda = 2.24 pm 0.05$ GHz and a orbital $g-$factor of $0.0186 pm 0.0005$. The reasons why this fine-structure has not been previously measured are discussed and strain-broadening is concluded to be the likely reason
The dependence of the luminescence of diamonds with negatively charged nitrogen-vacancy centers (NV-) vs. applied magnetic field (magnetic spectrum) was studied. A narrow line in zero magnetic field was discovered. The properties of this line are considerably different from those of other narrow magnetic spectrum lines. Its magnitude is weakly dependent of the orientation of the single-crystal sample to the external magnetic field. This line is also observed in a powdered sample. The shape of the line changes greatly when excitation light polarization is varied. The magnitude of the line has a non-linear relation to excitation light intensity. For low intensities this dependence is close to a square law. To explain the mechanism giving rise to this line in the magnetic spectrum, we suggest a model based on the dipole-dipole interaction between different NV- centers.
The conversion of neutral nitrogen-vacancy centers to negatively charged nitrogen-vacancy centers is demonstrated for centers created by ion implantation and annealing in high-purity diamond. Conversion occurs with surface exposure to an oxygen atmosphere at 465 C. The spectral properties of the charge-converted centers are investigated. Charge state control of nitrogen-vacancy centers close to the diamond surface is an important step toward the integration of these centers into devices for quantum information and magnetic sensing applications.
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