Na in diamond - high spin defects revealed by the ADAQ high-throughput computational database
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-05-23 |
| Journal | npj Computational Materials |
| Authors | Joel Davidsson, William Stenlund, Abhijith S. Parackal, Rickard Armiento, Igor A. Abrikosov |
| Institutions | Linköping University |
| Citations | 8 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research utilizes a high-throughput computational database (ADAQ) to screen over 21,600 point defects in diamond, identifying novel quantum emitters, particularly those involving sodium (Na).
- Database Achievement: The ADAQ database successfully identified all previously known diamond defects and uncovered several unexplored candidates with properties superior to the standard Nitrogen-Vacancy (NV) center.
- Sodium Substitutional (Nac): The Nac defect is predicted to be highly relevant due to its high spin states (S=1 and S=3/2) and a Zero Phonon Line (ZPL) located in the Near-Infrared (NIR) region (779 nm).
- High Debye-Waller Factor: Nac exhibits a significantly high predicted Debye-Waller (DW) factor (up to 83% without Jahn-Teller relaxation, 40% with), ensuring bright, robust photon emission. This is substantially higher than the NV centerâs ~3.2%.
- Biological Sensing Potential: The combination of NIR emission, high DW factor, and predicted low spectral diffusion makes Nac an ideal candidate for biological quantum sensing applications.
- Rare Spin-2 State: The Sodium Vacancy (NaV) cluster is one of only two defects predicted in the database to possess a rare Spin-2 ground state, offering extended possibilities for advanced spin control.
- Methodology: Initial screening used PBE DFT, followed by high-accuracy verification using the HSE06 hybrid functional to confirm the magneto-optical properties of the promising Na defects.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Defects Screened | 21,607 | Defects | ADAQ High-Throughput Database |
| Nac Neutral Spin State | 3/2 | S | Ground state stability |
| Nac Negative Spin State | 1 | S | Ground state stability |
| Nac Neutral ZPL (HSE) | 1.592 (779) | eV (nm) | Near-Infrared (First biological window) |
| Nac Negative ZPL (HSE) | 1.682 | eV | Near-Infrared |
| Nac Neutral DW Factor (HSE, JT Included) | 40 | % | Predicted robust photon emission |
| Nac Neutral DW Factor (HSE, JT Excluded) | 83 | % | Maximum predicted efficiency |
| Nac Negative ZFS (HSE D) | 6739 | MHz | Zero Field Splitting (D value) |
| Nac Formation Energy | ~13 | eV | Substitutional defect |
| NaV Negative Spin State | 2 | S | Predicted rare ground state |
| NV Center DW Factor (Experimental) | ~3.2 | % | Comparison baseline |
| Simulation Supercell Size | 512 | Atoms | 4 x 4 x 4 cubic cell |
| Simulation Lattice Constant | 3.57 | Angstrom | Diamond structure |
Key Methodologies
Section titled âKey MethodologiesâThe study employed a multi-stage computational workflow combining high-throughput screening with high-accuracy density functional theory (DFT) calculations.
- High-Throughput Screening (ADAQ): The Automatic Defect Analysis and Qualification (ADAQ) framework, built on the high-throughput toolkit (httk), was used to screen 21,607 single and double defects (s- and p-elements) in diamond.
- Initial DFT Parameters (PBE): Initial calculations utilized the Vienna Ab initio Simulation Package (VASP) with the semi-local Perdew, Burke, and Ernzerhof (PBE) functional for rapid screening of formation energy, spin, and ZPL.
- Simulation Environment: Defects were simulated in a 4 x 4 x 4 cubic supercell (512 atoms) at the gamma point, using a lattice constant of 3.57 Angstrom.
- High-Accuracy Verification (HSE06): Promising sodium defects were re-calculated using the HSE06 hybrid functional for improved accuracy in predicting electronic structure and optical properties.
- Pseudopotentials: Sodium was simulated with a 2p63s1 electron configuration (Na_pv), and Carbon with 2s22p2 (C).
- Phonon and Vibronic Analysis: Phonons for the neutral ground state were calculated using Phonopy. The Jahn-Teller (JT) stabilization energy (EJT) was determined by comparing relaxed structures.
- Optical Property Calculation: The Zero Phonon Line (ZPL) was calculated as the total energy difference between relaxed ground and excited states. Photoluminescence spectra and the Debye-Waller factor were computed using Pyphotonics.
- Spin Property Calculation: The Zero Field Splitting (ZFS) tensor was calculated using the VASP implementation, and transition dipole moments (TDM) were calculated using a modified version of PyVaspwfc.
Commercial Applications
Section titled âCommercial ApplicationsâThe identified sodium defects, particularly Nac, offer significant advantages over existing diamond quantum emitters (like the NV center) for several high-value commercial and research applications.
- Biological Quantum Sensing:
- The Nac ZPL (779 nm) falls within the first biological window, allowing for deeper tissue penetration with minimal absorption.
- The high Debye-Waller factor (up to 40%) ensures a bright, stable signal, critical for high-sensitivity in vivo magnetometry and relaxometry.
- Advanced Quantum Computing:
- High-spin states (S=3/2 for Nac, S=2 for NaV) provide extended Hilbert spaces, enabling complex spin control protocols and unique sensing opportunities for strain and temperature.
- Integrated Quantum Photonics:
- The high DW factor and strong Transition Dipole Moment (TDM) make Nac an efficient single-photon source, suitable for integration into diamond nanophotonics platforms and quantum-optical networks.
- Spectrally Stable Qubits:
- Predicted low spectral diffusion (due to small partial charge difference) suggests Nac may offer improved coherence and stability compared to the NV center, enhancing its viability as a solid-state quantum memory element.
View Original Abstract
Abstract Color centers in diamond are at the forefront of the second quantum revolution. A handful of defects are in use, and finding ones with all the desired properties for quantum applications is arduous. By using high-throughput calculations, we screen 21,607 defects in diamond and collect the results in the ADAQ database. Upon exploring this database, we find not only the known defects but also several unexplored defects. Specifically, defects containing sodium stand out as particularly relevant because of their high spins and predicted improved optical properties compared to the NV center. Hence, we studied these in detail, employing high-accuracy theoretical calculations. The single sodium substitutional (Na C ) has various charge states with spin ranging from 0.5 to 1.5, ZPL in the near-infrared, and a high Debye-Waller factor, making it ideal for biological quantum applications. The sodium vacancy (NaV) has a ZPL in the visible region and a potential rare spin-2 ground state. Our results show sodium implantation yields many interesting spin defects that are valuable additions to the arsenal of point defects in diamond studied for quantum applications.