Optical Spin Initialization of Nitrogen Vacancy Centers in a 28Si-Enriched 6H-SiC Crystal for Quantum Technologies
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2024-04-01 |
| Journal | Journal of Experimental and Theoretical Physics Letters |
| Authors | Fadis F. Murzakhanov, Margarita A. Sadovnikova, G. V. Mamin, D. V. Shurtakova, E. N. Mokhov |
| Institutions | Kazan Federal University, Ioffe Institute |
| Citations | 5 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research demonstrates successful optical spin initialization and characterization of Nitrogen-Vacancy (NV-) centers in high-purity, 28Si-enriched 6H-SiC crystals, establishing them as promising solid-state qubits.
- High Coherence Performance: Achieved exceptionally long electron spin relaxation times: T1 (longitudinal) = 1.3 ms and T2 (transverse) = 59 µs at 150 K (c || Bo orientation).
- Isotope Engineering: The use of 28Si-enriched SiC (nuclear spin I = 0) minimizes electron-nuclear coupling noise, resulting in extremely narrow EPR absorption lines (450 kHz FWHM).
- Optical Initialization: Effective spin alignment of the NV- ground state (Ms = 0) was achieved using nonresonant optical excitation at λ = 980 nm (3A → 3E transition).
- High-Frequency Characterization: Three structurally nonequivalent axial NV- center types were identified and characterized using high-frequency (94 GHz, 3.4 T) pulsed Electron Paramagnetic Resonance (EPR).
- Quantum Manipulation Potential: The combination of long relaxation times and narrow linewidths allows for highly selective excitation of resonant transitions, opening possibilities for complex quantum algorithms using optical, microwave, and radio-frequency pulse sequences.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Crystal Matrix | 6H-28SiC | N/A | Silicon isotope enriched (~99% 28Si, I=0) |
| Defect Center | NV- | N/A | Negatively charged Nitrogen-Vacancy (S=1) |
| Measurement Temperature | 150 | K | Optimal for photoactive defect observation |
| EPR Frequency | 94 | GHz | W band, pulsed EPR |
| Magnetic Field (Bo) | 3.4 | T | High-field regime (Zeeman interaction dominates) |
| Excitation Wavelength (λ) | 980 | nm | Nonresonant optical excitation |
| Transverse Relaxation Time (T2) | 59 | µs | c |
| Longitudinal Relaxation Time (T1) | 1.3 | ms | c |
| EPR Linewidth (FWHM) | 450 | kHz | Extremely narrow absorption lines |
| Electron Fluence (Irradiation) | 4 x 1018 | cm-2 | Used for vacancy defect formation |
| Fine Structure Splitting (D) (NVk1k2) | 1358 ± 2 | MHz | Axial NV center type |
| Fine Structure Splitting (D) (NVhh) | 1331 ± 2 | MHz | Axial NV center type |
| Fine Structure Splitting (D) (NVk2k1) | 1282 ± 2 | MHz | Axial NV center type |
| Hyperfine Interaction (A) | ~1 | MHz | Weak interaction with 14N (I=1) nuclei |
Key Methodologies
Section titled “Key Methodologies”The characterization relied on a sequence of material preparation steps followed by advanced pulsed EPR techniques:
- Crystal Growth: Bulk 6H-SiC crystals were grown via high-temperature physical vapor deposition (PVT) using a precursor enriched with the nonmagnetic 28Si isotope (I = 0) to achieve ~99% purity.
- Defect Induction: Crystals were irradiated with 2-MeV electrons at a fluence of 4 x 1018 cm-2 to create silicon and carbon vacancy defects.
- NV- Formation: Irradiated crystals were annealed in an argon atmosphere at T = 900 °C for 2 hours, optimizing the formation of stable NV- centers.
- Photoinduced EPR: Experiments were conducted using a commercial Bruker Elexsys E680 spectrometer (94 GHz, 3.4 T) at T = 150 K, coupled with a 980 nm continuous-wave laser for optical excitation and spin alignment.
- T2 Measurement: The transverse relaxation time was measured using the Hahn pulse sequence (π/2 - τ - π), detecting the electron spin echo integral intensity as a function of the delay time τ.
- T1 Measurement: The longitudinal relaxation time was measured using the “inversion-recovery” sequence (π - T - π/2 - τ - π), varying the time T between the inverting pulse and the detection sequence.
Commercial Applications
Section titled “Commercial Applications”The demonstrated optical spin initialization and long coherence times in robust SiC matrices are critical for next-generation quantum technologies.
- Solid-State Quantum Bits (Qubits): NV- centers in SiC are direct candidates for scalable solid-state qubits, offering a pathway to integrate quantum devices into existing semiconductor platforms.
- Quantum Sensing: The high sensitivity of the NV- spin state to external fields enables the development of highly sensitive nanosensors for:
- Magnetic field detection (magnetometry).
- Temperature and pressure monitoring.
- Quantum Cryptography: The ability to initialize and read out spin states optically supports the implementation of basic quantum cryptography protocols.
- Near-Infrared Single-Photon Sources: The luminescence spectrum of SiC NV- centers (1.1-1.25 µm) falls within the O band, making them ideal single-photon sources for long-distance optical fiber information transmission.
- Quantum Spintronics: The creation of a robust “photon-spin” interface allows for the fabrication of quantum spintronic elements, leveraging the spin alignment achieved through optical excitation.
View Original Abstract
High-spin defect centers in crystal matrices are used in quantum computing technologies, highly sensitive sensors, and single-photon sources. In this work, optically active nitrogen-vacancy color centers NV - in a 28 Si-enriched (nuclear spin $$I = 0$$ ) 6H- 28 SiC crystal have been studied using the photoinduced ( $$\lambda $$ = 980 nm) high-frequency (94 GHz, 3.4 T) pulsed electron paramagnetic resonance method at a temperature of $$T = 150{\kern 1pt} $$ K. Three structurally nonequivalent types of NV - centers with axial symmetry have been identified and their spectroscopic parameters have been determined. Long spin-lattice, $${{T}{1}} = 1.3{\kern 1pt} $$ ms, and spin-spin, $${{T}{2}} = 59{\kern 1pt} $$ μs, ensemble relaxation times of NV - centers with extremely narrow (450 kHz) absorption lines allow highly selective excitation of resonant transitions between sublevels $$({{m}_{I}})$$ caused by the weak hyperfine interaction $$(A \approx 1{\kern 1pt} $$ MHz) with 14 N $$(I = 1)$$ nuclei for the quantum manipulation of the electron spin magnetization.