We report the development of an experimental approach that can characterize the energy level structure of an individual silicon vacancy (SiV) center in a magnetic field and extract the key parameters for the energy level structure. This approach builds upon a theoretical model that includes effects of the static strain, dynamic Jahn-Teller coupling, and magnetic field and introduces two coupling rates, one each for the ground and the excited states, to characterize the combined effects of strain and Jahn-Teller coupling. With the use of an analytical expression for the energy level structure of the SiV center under a transverse magnetic field, these two coupling rates can be directly derived from the measurement of the frequency separation between two spin-conserved transitions in a photoluminescence excitation spectrum and the measurement of the coherent population trapping resonance related to the SiV ground spin states. Additional experimental studies on the dependence of the energy level structure on the magnetic field amplitude and direction further verify the theoretical model and reveal contributions from unequal orbital magnetic coupling for the ground and excited states.
We report the development of an experimental approach to efficiently determine the energy level structure of an individual silicon vacancy (SiV) center in a magnetic field along an arbitrary direction. This approach uses two coupling rates (one each for the ground and the excited states) to characterize the combined effects of static strain and dynamic Jahn-Teller coupling and exploits the fact that orbital Zeeman effects vanish when the magnetic field is normal to the SiV axis. With an analytical expression for the energy level structure of the SiV under a transverse magnetic field, the two coupling rates can be directly derived from two measurements: one on the frequency separation between two spin-conserved transitions and the other on the coherent population trapping resonance of the SiV ground spin states. A detailed comparison between the numerical calculation and the experimental result on the dependence of the spin-conserved splitting on both the amplitude and direction of the magnetic field further reveals unequal orbital magnetic coupling for the ground and excited states, indicating that unequal orbital quenching factors are needed for an accurate description of the SiV energy level structure in a magnetic field.
The neutral silicon--vacancy (SiV
0) center in diamond combines inversion symmetry with optical emission, making it a robust quantum emitter resilient to stray electric fields. Using first-principles density-functional theory, we quantify its response to isotropic strain spanning strong compression and tensile regimes (effective hydrostatic pressures of approximately
−80 to
180~GPa). The coexistence of doubly degenerate
eg and
eu levels produces a structural instability captured by a quadratic product Jahn--Teller model. Under isotropic compression, the zero-phonon line blue-shifts nearly linearly while the
Eg phonon stiffens, suppressing vibronic instabilities and reducing Jahn--Teller quenching. Consequently, the Ham-reduced excited-state spin--orbit splitting increases substantially and the dark--bright vibronic gap widens. In contrast, isotropic tensile strain enhances vibronic effects and induces symmetry breaking beyond a critical strain, with tunneling-mediated dynamical averaging at the onset. Throughout the symmetry-preserving regime, parity remains well defined, so isotropic strain alone does not activate the dark transition. Charge-transition levels indicate photostability of the emission deep into the compressive regime, and near the highest photostable deformation (
∼100~GPa), the radiative lifetime increases due to a reduced transition dipole moment despite the increasing optical energy. These trends yield compact calibration relations linking optical and spin observables to isotropic strain and establish SiV
0 as a symmetry-protected, strain-tunable quantum emitter operating into the multi-megabar-equivalent regime.
The negatively charged silicon vacancy (SiV) color center in diamond has recently proven its suitability for bright and stable single photon emission. However, its electronic structure so far has remained elusive. We here explore the electronic structure by exposing single SiV defects to a magnetic field where the Zeeman effect lifts the degeneracy of magnetic sublevels. The similar responses of single centers and a SiV ensemble in a low strain reference sample prove our ability to fabricate almost perfect single SiVs, revealing the true nature of the defect's electronic properties. We model the electronic states using a group-theoretical approach yielding a good agreement with the experimental observations. Furthermore, the model correctly predicts polarization measurements on single SiV centers and explains recently discovered spin selective excitation of SiV defects.
We investigate the magnetic field dependent photophysics of individual nitrogen-vacancy (NV) color centers in diamond under cryogenic conditions. At distinct magnetic fields, we observe significant reductions in the NV photoluminescence rate, which indicate a marked decrease in the optical readout efficiency of the NV's ground state spin. We assign these dips to excited state level anticrossings, which occur at magnetic fields that strongly depend on the effective, local strain environment of the NV center. Our results offer new insights into the structure of the NVs' excited states and a new tool for their effective characterization. Using this tool, we observe strong indications for strain-dependent variations of the NV's orbital g factor, obtain new insights into NV charge state dynamics, and draw important conclusions regarding the applicability of NV centers for low-temperature quantum sensing.
The negatively charged silicon-vacancy (SiV${}^{\ensuremath{-}}$) center in diamond is a promising single-photon source for quantum communications and information processing. However, the center's 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 $\ensuremath{\langle}111\ensuremath{\rangle}$ aligned split-vacancy structure with
D3d symmetry. Furthermore, we identify an additional electronic level and evidence for the presence of dynamic Jahn-Teller effects in the center's 738-nm optical resonance.
Color centers in diamond are important quantum emitters for a broad range of applications ranging from quantum sensing to quantum optics. Understanding the internal energy level structure is of fundamental importance for future applications. We experimentally investigate the level structure of an ensemble of few negatively charged silicon-vacancy (SiV − ) and germanium-vacancy (GeV − ) centers in bulk diamond at room temperature by photoluminescence (PL) and excitation (PLE) spectroscopy over a broad wavelength range from 460 to and perform power-dependent saturation measurements. For SiV − our experimental results confirm the presence of a higher energy transition at . By comparison with detailed theoretical simulations of the imaginary dielectric function we interpret the transition as a dipole-allowed transition from -state to -state where the corresponding a 2 u -level lies deeply inside the diamond valence band. Therefore, the transition is broadened by the diamond band. At higher excitation power of we indicate signs of a parity-conserving transition at supported by saturation measurements. For GeV − we demonstrate that the PLE spectrum is in good agreement with the mirror image of the PL spectrum of the zero-phonon line. Experimentally we do not observe a higher lying energy level up to a transition wavelength of . The observed PL spectra are identical, independent of excitation wavelength, suggesting a rapid decay to excited state and followed by optical transition to ground state. Our investigations convey important insights for future quantum optics and quantum sensing experiments based on SiV − -center and GeV − -center in diamond.