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 |
Executive Summary
Section titled âExecutive SummaryâThis research predicts a new class of diamond quantum emittersâGroup III Vacancy (XV-) centersâthat combine the most desirable traits of existing diamond color centers for quantum technology applications.
- Stable Spin-1 Ground State: The thermodynamically preferred negative charge state (XV-, where X = Al, Ga, In) exhibits a stable Spin-1 electronic ground state, analogous to the highly utilized Nitrogen Vacancy (NV-) center.
- Spectral Stability: The centers adopt an inversion-symmetric split-vacancy (D3d) structure, eliminating a permanent electric dipole moment. This makes their optical transitions insensitive to electric field noise, ensuring high spectral stability, similar to the Silicon Vacancy (SiV-) center.
- High Emission Efficiency: Calculations predict a relatively high Debye-Waller factor (DWF), indicating a large fraction of photons are emitted into the coherent Zero Phonon Line (ZPL), promising improved efficiency for photon-mediated entanglement.
- Wavelength Diversity: Predicted ZPL energies span a range from 437 nm (TlV-) to 679 nm (GaV-), offering flexibility for integration into various photonic architectures.
- Jahn-Teller Effect Captured: The study accurately characterizes the strong Product Jahn-Teller (pJT) effect in the excited state manifold, which causes symmetry-breaking distortions (D3d to C2h). Capturing this effect is critical for precise ZPL energy prediction.
- Thermodynamic Stability: AlV-, GaV-, and InV- are found to be thermodynamically stable in the -1 charge state in intrinsic diamond, making them viable targets for experimental realization in as-grown samples.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Ground State Spin | 1 | N/A | Stable negative charge state (XV-) |
| Ground State Symmetry | D3d | N/A | Inversion symmetric; insensitive to electric field noise |
| Excited State Distortion | D3d â C2h | N/A | Symmetry breaking due to Product Jahn-Teller (pJT) effect |
| GaV- ZPL Energy | 1.82 (679) | eV (nm) | Predicted Zero Phonon Line energy |
| InV- ZPL Energy | 2.12 (584) | eV (nm) | Predicted Zero Phonon Line energy |
| TlV- ZPL Energy | 2.84 (437) | eV (nm) | Predicted Zero Phonon Line energy |
| GaV- Jahn-Teller Instability (Î) | 236 | meV | Energy difference between D3d and C2h minima |
| InV- Jahn-Teller Instability (Î) | 175 | meV | Energy difference between D3d and C2h minima |
| TlV- Jahn-Teller Instability (Î) | 148 | meV | Energy difference between D3d and C2h minima |
| GaV- Energy Barrier (δ) | 71 | meV | Barrier caused by higher-order phonon coupling |
| Supercell Size | 512 | atoms | DFT calculation size |
| Plane-Wave Energy Cutoff | 80 | Ry | Used for constrained DFT (ASCF) calculations |
Key Methodologies
Section titled âKey MethodologiesâThe properties of the Group III vacancy defects (XV) were characterized using ab initio electronic structure theory, primarily Density Functional Theory (DFT).
- Ground State Electronic Structure: DFT calculations were performed using the HSE06 hybrid functional to accurately model the electronic properties and band gap of the diamond host and the defect orbitals.
- Thermodynamic Stability: Charge transition levels (Îľ(q1/q2)) were calculated using total energy differences (Etot) from supercell calculations, incorporating charge corrections (Ecorr) to account for periodic interactions between charged defects.
- Excited State Relaxation and pJT Effect: The excited electronic state manifold was investigated using Constrained DFT (ASCF) within Quantum Espresso, employing norm-conserving pseudopotentials and a plane-wave basis. This method captured the symmetry-breaking distortions (D3d â C2h) caused by the Product Jahn-Teller (pJT) effect.
- Phonon Properties: Phonon properties for the ground state geometries were evaluated using the computationally efficient PBE functional.
- Optical Spectra Simulation: Emission lineshapes, including ZPL energies and Debye-Waller factors, were calculated based on the overlap of ionic vibrational wavefunctions between the relaxed excited state and the ground state, using a generating function approach.
Commercial Applications
Section titled âCommercial ApplicationsâThe predicted combination of a stable spin-1 ground state and high spectral stability makes Group III Vacancy centers highly promising for next-generation quantum technologies.
- Scalable Quantum Networks: The stable spin and symmetry-protected optical transitions are ideal for use as stationary qubits and high-fidelity photon emitters, enabling long-distance quantum communication.
- Solid-State Quantum Computing: The Spin-1 ground state provides a robust platform for encoding quantum information in solid-state diamond devices.
- High-Coherence Quantum Sensing: The D3d inversion symmetry ensures the centers are spectrally stable and insensitive to local electric field noise, crucial for high-precision magnetometry and sensing near diamond surfaces.
- High-Rate Entanglement Generation: The high predicted Debye-Waller factors (ZPL emission efficiency) will significantly increase the rate of photon emission into the coherent line, accelerating entanglement generation protocols compared to current NV- systems.
- Integrated Photonics: The ZPL wavelengths, spanning visible to near-UV (437 nm to 679 nm), allow for tailored integration into various micro- and nano-cavity structures to enhance spontaneous emission.
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.