Group-III quantum defects in diamond are stable spin-1 color centers
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-11-24 |
| Journal | Physical review. B./Physical review. B |
| Authors | Isaac Harris, Christopher J. Ciccarino, Johannes Flick, Dirk Englund, Prineha Narang |
| Institutions | Harvard University, Massachusetts Institute of Technology |
| Citations | 37 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Group III Quantum Defects in Diamond
Section titled âTechnical Documentation & Analysis: Group III Quantum Defects in DiamondâThis document analyzes the theoretical predictions regarding Group III vacancy centers (AIV, GaV, InV, TlV) in diamond, which are proposed as stable Spin-1 color centers. The analysis focuses on extracting key technical specifications and aligning them with 6CCVDâs advanced MPCVD diamond capabilities to support experimental realization and device integration.
Executive Summary
Section titled âExecutive SummaryâThe research predicts a new class of diamond quantum emittersâGroup III vacancy centers (XV-)âthat exhibit highly desirable properties for quantum information science, combining the best features of existing color centers.
- Stable Spin-1 Ground State: The defects are predicted to have a stable S = 1 electronic ground state, analogous to the highly utilized Nitrogen Vacancy (NV) center.
- Spectral Stability: The ground state adopts an inversion-symmetric D3d configuration, eliminating a permanent electric dipole moment and making optical transitions insensitive to electric field noise (similar to the Silicon Vacancy, SiV).
- High Efficiency: Calculations predict a high Zero Phonon Line (ZPL) emission efficiency, characterized by a high Debye-Waller factor, significantly exceeding that of the NV- center.
- Thermodynamic Stability: AIV, GaV, and InV are thermodynamically stable in the preferred -1 charge state in intrinsic diamond, simplifying material requirements.
- Wavelength Range: Predicted ZPL emission spans a wide range, from the blue (437 nm for TlV-) to the red/near-infrared (679 nm for GaV-).
- Methodology: Predictions rely on rigorous ab initio electronic structure theory, including Density Functional Theory (DFT) with the HSE06 hybrid functional and analysis of the product Jahn-Teller (pJT) effect in the excited state manifold.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the critical predicted properties of the Group III vacancy centers, essential for guiding experimental efforts.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Stable Charge State (AIV, GaV, InV) | -1 | Charge | Thermodynamically preferred in intrinsic diamond |
| Ground State Spin | S = 1 | Spin | Ideal for quantum networking and sensing applications |
| Ground State Symmetry | D3d | Geometry | Inversion symmetric, protecting transitions from electric field noise |
| Excited State Minimum Symmetry | C2h | Geometry | Result of strong electron-phonon coupling (pJT effect) |
| ZPL Energy (GaV-) | 1.82 / 679 | eV / nm | Predicted Zero Phonon Line (Red/NIR) |
| ZPL Energy (InV-) | 2.12 / 584 | eV / nm | Predicted Zero Phonon Line (Orange) |
| ZPL Energy (TlV-) | 2.84 / 437 | eV / nm | Predicted Zero Phonon Line (Blue) |
| Jahn-Teller Instability (GaV-, Î) | 236 | meV | Energy difference between D3d and C2h minima |
| Emission Efficiency | High | Factor | High Debye-Waller factor (higher than NV-) |
| Computational Supercell Size | 512 | Atoms | Used for DFT calculations |
Key Methodologies
Section titled âKey MethodologiesâThe theoretical characterization of the Group III vacancy centers involved advanced computational techniques to accurately model ground and excited state properties, as well as electron-phonon coupling.
- Electronic Structure Calculation: Density Functional Theory (DFT) utilizing the HSE06 hybrid functional was employed to investigate the electronic properties of Al, Ga, In, and Tl vacancies.
- Charge Transition Level Calculation: Thermodynamic stability was determined by calculating charge transition levels (Δ(q1/q2)) using total energy calculations from a 512-atom supercell, incorporating charge corrections for periodic interactions.
- Excited State Relaxation: Constrained DFT (ASCF) was used to relax the system in the excited electronic state, identifying both the high-symmetry D3d point and the lower-symmetry C2h energy minima.
- Jahn-Teller Analysis: The product Jahn-Teller (pJT) effect was characterized by mapping the potential energy surface between D3d and C2h geometries, quantifying the instability (Î) and energy barrier (ÎŽ).
- Optical Lineshape Prediction: Ab initio emission lineshapes were calculated by evaluating the overlap of ionic vibrational wavefunctions between the relaxed excited state and the ground state, using phonon properties derived from the PBE functional.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful experimental realization and integration of Group III vacancy centers into quantum devices require ultra-high purity diamond substrates, precise dimensional control, and advanced surface engineering. 6CCVD is uniquely positioned to supply the necessary materials and fabrication services.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate and extend this research, the primary material requirement is high-quality, intrinsic diamond to ensure the thermodynamic stability of the desired -1 charge state and minimize background noise.
- Optical Grade Single Crystal Diamond (SCD): Essential for achieving the low native defect concentration required for stabilizing the XV- centers and maximizing spin coherence times.
- Substrate Thickness: We offer SCD plates from 0.1”m up to 500”m, allowing flexibility for both thin-film device integration (e.g., photonic crystal cavities) and robust substrates (up to 10mm thickness).
- Boron-Doped Diamond (BDD): While the paper focuses on intrinsic diamond, BDD may be required for precise Fermi level control in future experiments, particularly for stabilizing the TlV center in the -1 state.
Customization Potential
Section titled âCustomization PotentialâExperimental implementation of these predicted emittersâespecially coupling them to photonic structuresâdemands highly customized substrates and precise surface preparation.
| Research Requirement | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| Ion Implantation Substrates | Custom Dimensions up to 125mm (PCD) | Provides large-area substrates for high-throughput ion implantation of Group III elements (Al, Ga, In, Tl) and subsequent annealing. |
| Photonic Device Integration | Ultra-Low Roughness Polishing (Ra < 1nm) | SCD surfaces are polished to Ra < 1nm, minimizing surface noise and spectral diffusion, which is critical for achieving the predicted high ZPL efficiency and coupling emitters to micro/nanocavities. |
| Charge State Control & Sensing | Custom Metalization Services | We offer in-house deposition of Au, Pt, Pd, Ti, W, and Cu. This is crucial for fabricating electrodes necessary to control the charge state of the XV centers or integrate them into quantum sensing platforms. |
| Specific Crystal Orientation | Custom Substrate Orientation | We supply diamond substrates cut and polished to specific crystallographic orientations (e.g., [111] or [100]), optimizing the alignment of the D3d defect axis for maximum collection efficiency. |
Engineering Support
Section titled âEngineering SupportâThe theoretical predictions highlight the need for precise material engineering to achieve the combination of stable spin and optical properties.
- Material Selection for Group III Vacancy Projects: 6CCVDâs in-house PhD team specializes in MPCVD growth parameters and can assist researchers in selecting the optimal diamond material (e.g., nitrogen concentration, isotopic purity) necessary to replicate or extend the predicted properties of these novel Spin-1 color centers.
- Defect Creation Consultation: We provide consultation on substrate preparation and post-processing requirements (e.g., annealing protocols) to maximize the yield and stability of implanted Group III defects.
- Global Logistics: We ensure reliable global shipping (DDU default, DDP available) of sensitive, high-value diamond materials directly to research facilities worldwide.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Color centers in diamond have emerged as leading solid-state âartificial atomsâ for a range of quantum technologies, from quantum sensing to quantum networks. Concerted research activities are now underway to identify new color centers that combine stable spin and optical properties of the nitrogen vacancy (NV<sup>-</sup>) with the spectral stability of the silicon vacancy (SiV<sup>-</sup>) centers in diamond, with recent research identifying other group-IV color centers with superior properties. In this paper, we investigate a class of diamond quantum emitters from first principles, the group-III color centers, which we show to be thermodynamically stable in a spin-1, electric-field-insensitive structure. Further, from ab initio electronic structure methods, we characterize the product Jahn-Teller (pJT) effect present in the excited-state manifold of these group-III color centers, where we capture symmetry-breaking distortions associated with strong electron-phonon coupling. These predictions can guide experimental identification of group-III vacancy centers and their use in applications in quantum information science and technology.