Optically Detected Magnetic Resonance in Neutral Silicon Vacancy Centers in Diamond via Bound Exciton States
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-11-30 |
| Journal | Physical Review Letters |
| Authors | Zi-Huai Zhang, Paul Stevenson, GergĆ Thiering, Brendon C. Rose, Ding Huang |
| Institutions | Element Six (United Kingdom), Princeton University |
| Citations | 53 |
| Analysis | Full AI Review Included |
Optically Detected Magnetic Resonance in Neutral Silicon Vacancy Centers in Diamond via Bound Exciton States: Technical Analysis
Section titled âOptically Detected Magnetic Resonance in Neutral Silicon Vacancy Centers in Diamond via Bound Exciton States: Technical AnalysisâExecutive Summary
Section titled âExecutive Summaryâ- First ODMR Demonstration: The paper reports the first successful observation of Optically Detected Magnetic Resonance (ODMR) and coherent control in neutral silicon vacancy (SiV0) centers in diamond.
- Bound Exciton (BE) Enabling Mechanism: ODMR was enabled by the discovery and utilization of previously unreported higher-lying excited states (825-890 nm), which are assigned as Bound Exciton (BE) states.
- High Spin Polarization: Excitation via these BE states achieves highly efficient bulk spin polarization (up to 60%), providing a new manifold for spin initialization and readout.
- Excellent Coherence Properties: Measured spin coherence time (T2) is 55.5 ”s at 6 K in the low magnetic field regime, and the spin relaxation time (T1) is measured to be longer than 30 ms at 6 K.
- Mitigation of Spectral Diffusion: SiV0âs inversion symmetry minimizes spectral diffusion and guarantees >90% emission into the Zero-Phonon Line (ZPL), making it superior to defects like the NV center for quantum networks.
- Theoretical Validation: Group theory and Density Functional Theory (DFT) calculations support the BE assignment, showing Rydberg scaling for p-like transitions and consistency with the ionization threshold (1.53 eV).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Spin Coherence Time (T2) | 55.5 ± 10.6 | ”s | Measured at 6 K using Hahn echo sequence, low magnetic field. |
| Spin Dephasing Time (T2*) | 202 ± 16 | ns | Measured at 6 K using Ramsey sequence. |
| Spin Relaxation Time (T1) | >30 | ms | Measured at 6 K, no decay observed up to this limit. |
| Spin Relaxation Time (T1) | 1.38 ± 0.21 | ms | Measured at 50 K, limited by Orbach process. |
| CW ODMR Central Peak | 944 | MHz | Associated with 28Si and 30Si isotopes. |
| ODMR Hyperfine Transition | 912 | MHz | Lower frequency 29Si hyperfine transition used for pulsed control. |
| SiV0 Concentration (Sample D1) | 4.0 x 1016 | cm-3 | Bulk CVD grown, 29Si enriched. |
| Optical Spin Polarization (OSP) | 40-60 | % | Achieved via Bound Exciton (BE) state excitation. |
| BE Transition Wavelength Range | 825 to 890 | nm | Higher-lying excited states used for efficient spin polarization. |
| SiV0 ZPL Wavelength | 946 | nm | Emission wavelength used for PLE and ODMR detection. |
| Fitted Ionization Energy (EI) | 1.53 | eV | Extracted from Rydberg scaling fit of BE states. |
| Fitted Rydberg Energy (Ey) | 0.4 | eV | Consistent with effective-mass description. |
| ODMR Activation Energy (Eb) | 50.8 ± 4.6 | meV | Lower hyperfine line, extracted from contrast temperature dependence. |
| Inhomogeneous Linewidth (T2* limit) | 1.47 ± 0.44 | MHz | Extracted from power-dependent CW ODMR spectra. |
Key Methodologies
Section titled âKey Methodologiesâ- Sample Preparation: Three diamond samples were studied: two bulk-doped (D1, D2) and one implanted (D3). Samples D1 and D2 were grown via Chemical Vapor Deposition (CVD) using 90% 29Si enriched silicon precursor, followed by high-pressure/high-temperature annealing.
- Spectroscopy: Optical properties were correlated using three techniques at 5.5 K:
- Absorption Spectroscopy: Measured narrow absorption peaks (near 830, 855, 870 nm).
- Photoluminescence Excitation (PLE): Excitation wavelengths were swept while detecting the 946 nm SiV0 ZPL emission, confirming the transitions are associated with SiV0.
- Optical Spin Polarization (OSP): Measured spin polarization efficiency after excitation at various wavelengths using pulsed X-band ESR (Hahn echo sequence).
- ODMR Setup: Continuous-wave (CW) and pulsed ODMR were performed at cryogenic temperatures (6 K) using a tunable Ti:Sapphire laser for excitation (e.g., 855.65 nm BE transition). Microwave (MW) excitation was applied via a 70 ”m wire stretched across the sample.
- Pulsed Coherent Control: Rabi oscillations were measured using pulsed ODMR on the 912 MHz 29Si hyperfine transition. T2* (dephasing) was measured using a Ramsey sequence, and T2 (coherence) was measured using a Hahn echo sequence.
- Spin Dynamics Measurement: Spin relaxation time (T1) was measured using pulsed ODMR by varying the dark time between initialization and readout pulses, showing a transition to Orbach-limited decay at higher temperatures (50 K).
- Theoretical Modeling (DFT/ASC F): The electronic structure and BE states were modeled using DFT (VASP code) and the ASCF method (electron-hole interaction and ionic relaxation) to calculate ionization thresholds, crystal field splitting, and spin-orbit coupling parameters, validating the Rydberg scaling observed experimentally.
Commercial Applications
Section titled âCommercial Applicationsâ- Quantum Computing and Memory: SiV0 centers are prime candidates for solid-state quantum memories due to their long T1 (>30 ms) and T2 (55.5 ”s) times at cryogenic temperatures, combined with robust optical interfaces.
- Quantum Networks and Repeaters: The high fraction of ZPL emission (>90%) and the new efficient spin initialization/readout scheme via BE states significantly improve entanglement generation rates over defects like the NV center.
- Cryogenic Quantum Sensing: The ability to perform ODMR and coherent control at low magnetic fields enables the development of highly sensitive magnetic and electric field sensors operating in cryogenic environments.
- Advanced Diamond Materials Manufacturing: Requires precise control over CVD growth and doping (especially isotopic enrichment, e.g., 29Si) to achieve high concentrations of high-quality SiV0 centers, driving innovation in diamond synthesis.
- Platform for Emerging Defects: The BE state control methodology is transferable to other neutral Group IV vacancy centers (e.g., SnV0, GeV0) and neutral divacancy centers in SiC, accelerating the development of new quantum platforms.
View Original Abstract
Neutral silicon vacancy (SiV^{0}) centers in diamond are promising candidates for quantum networks because of their excellent optical properties and long spin coherence times. However, spin-dependent fluorescence in such defects has been elusive due to poor understanding of the excited state fine structure and limited off-resonant spin polarization. Here we report the realization of optically detected magnetic resonance and coherent control of SiV^{0} centers at cryogenic temperatures, enabled by efficient optical spin polarization via previously unreported higher-lying excited states. We assign these states as bound exciton states using group theory and density functional theory. These bound exciton states enable new control schemes for SiV^{0} as well as other emerging defect systems.