We report measurements of optically detected magnetic resonance spectra of ensembles of nitrogen-vacancy (NV-) centers in diamonds in the presence of electromagnetic fields. To reduce inhomogeneous broadening, the spectra are acquired from a region of 20 cubic microns in a CVD(Chemical Vapor Deposition) diamond through a confocal microscope. The Stark shift from transverse electric fields is enhanced at avoided crossings between the hyperfine levels that arise from interaction with 14N(I = 1) nuclei in the diamond lattice. As expected from previous reports, the Stark shift of the spectral lines is stronger when there is no magnetic field along the NV axis. The shift is also strong, but for different transitions, at a field of about 100 uT.
The negatively charged nitrogen vacancy (NV${}^{\ensuremath{-}}$) center in diamond is a well-known color center with interesting applications in nanoscale sensing and quantum metrology, due to its high sensitivity to minute local electric, magnetic, and strain fields. Motivated by these applications of the this center, the authors employ here first-principles calculations based on quantum embedding to derive a many-body description of its excited-state dipole couplings and strain susceptibilities, which underlie the electric field and strain induced Stark effects.
Diamond nitrogen-vacancy (NV) centers are widely studied for quantum sensing in multiple physical fields due to their long coherence time and room-temperature optical readout. However, accurately decoupling and extracting signals for individual fields from fluorescence remains a major challenge. In this work, by establishing the spatial configuration between the four axes of the NV center and the directions of the externally applied electric and magnetic fields, the resonance frequency shifts of two pairs in the ODMR spectrum are exclusively induced by the electric field, whereas those of the other two pairs are exclusively induced by the magnetic field. Consequently, effective decoupling and readout of the electric field signal are realized. The experiments measure electric fields from 0 to 20 kV/cm in the diamond sample, revealing a linear relationship between the resonance frequency shift and the applied electric field, with coefficients 0.1713MHz/(kV/cm) and 0.1660MHz/(kV/cm) matching the NV center’s linear Stark effect, laying the foundation for subsequent research on electric field measurement.
The negatively charged nitrogen-vacancy (NV
−) center in diamond has shown great potential in nanoscale sensing and quantum information processing due to its rich spin physics. An efficient coupling with light, providing strong luminescence, is crucial for realizing these applications. Laser-written waveguides in diamond promote NV
− creation and improve their coupling to light but, at the same time, induce strain in the crystal. The induced strain contributes to light guiding but also affects the energy levels of NV
− centers. We probe NV
− spin states experimentally with the commonly used continuous-wave zero-field optically detected magnetic resonance (ODMR). In our waveguides, the ODMR spectra are shifted, split, and consistently asymmetric, which we attribute to the impact of local strain. To understand these features, we model ensemble ODMR signals in the presence of strain. By fitting the model results to the experimentally collected ODMR data, we determine the strain tensor components at different positions, thus determining the strain profile across the waveguide. This shows that zero-field ODMR spectroscopy can be used as a strain imaging tool. The resulting strain within the waveguide is dominated by a compressive axial component transverse to the waveguide structure, with a smaller contribution from vertical and shear strain components.
The NV
− color center in diamond has been demonstrated as a powerful nanosensor for quantum metrology due to the sensitivity of its optical and spin properties to external electric, magnetic, and strain fields. In view of these applications, we use quantum embedding to derive a many-body description of strain and charge induced Stark effects on the NV
− center. We quantify how strain longitudinal to the axis of NV
− shifts the excited states in energy, while strain with a component transverse to the NV
− axis splits the degeneracies of the
3E and
1E states. The largest effects are for the optically relevant
3E manifold, which splits into
Ex and
Ey with transverse strain. From these responses we extract strain susceptibilities for the
Ex/y states within the quasi-linear regime. Additionally, we study the many-body dipole matrix elements of the NV
− and find a permanent dipole 1.64 D at zero strain, which is somewhat smaller than that obtained from recent density functional theory calculations. We also determine the transition dipole between the
Ex and
Ey and how it evolves with strain.
Characterizing the local internal environment surrounding solid-state spin defects is crucial to harnessing them as nanoscale sensors of external fields. This is especially germane to the case of defect ensembles which can exhibit a complex interplay between interactions, internal fields, and lattice strain. Working with the nitrogen-vacancy (NV) center in diamond, we demonstrate that local electric fields dominate the magnetic resonance behavior of NV ensembles at a low magnetic field. We introduce a simple microscopic model that quantitatively captures the observed spectra for samples with NV concentrations spanning more than two orders of magnitude. Motivated by this understanding, we propose and implement a novel method for the nanoscale localization of individual charges within the diamond lattice; our approach relies upon the fact that the charge induces a NV dark state which depends on the electric field orientation.