| 1. |
- Haykal, A., et al.
(författare)
-
Decoherence of V-B(-) spin defects in monoisotopic hexagonal boron nitride
- 2022
-
Ingår i: Nature Communications. - : Nature Portfolio. - 2041-1723. ; 13:1
-
Tidskriftsartikel (refereegranskat)abstract
- Spin defects in hexagonal boron nitride (hBN) are promising quantum systems for the design of flexible two-dimensional quantum sensing platforms. Here we rely on hBN crystals isotopically enriched with either B-10 or B-11 to investigate the isotope-dependent properties of a spin defect featuring a broadband photoluminescence signal in the near infrared. By analyzing the hyperfine structure of the spin defect while changing the boron isotope, we first confirm that it corresponds to the negatively charged boron-vacancy center (V-B(-)). We then show that its spin coherence properties are slightly improved in B-10-enriched samples. This is supported by numerical simulations employing cluster correlation expansion methods, which reveal the importance of the hyperfine Fermi contact term for calculating the coherence time of point defects in hBN. Using cross-relaxation spectroscopy, we finally identify dark electron spin impurities as an additional source of decoherence. This work provides new insights into the properties of V-B(-) spin defects, which are valuable for the future development of hBN-based quantum sensing foils.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Csore, A., et al.
(författare)
-
Fluorescence spectrum and charge state control of divacancy qubits via illumination at elevated temperatures in 4H silicon carbide
- 2022
-
Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 105:16
-
Tidskriftsartikel (refereegranskat)abstract
- Divacancy in its neutral charge state () in 4H silicon carbide (SiC) is a leading quantum bit (qubit) contender. Owing to the lattice structure of 4H SiC, four different VCVSi configurations can be formed. The ground and the optically accessible excited states of configurations exhibit a high-spin state, and the corresponding optical transition energies are around ≈1.1eV falling in the near-infrared wavelength region. Recently, photoluminescence (PL) quenching has been experimentally observed for all configurations in 4H SiC at cryogenic temperatures. It has been shown that is converted to and it remains in this shelving dark state at cryogenic temperatures until photoexcitation with the threshold energies or above is applied to convert back to . In this study, we demonstrate both in experiments and theory that the threshold energy for reionization is temperature dependent. We carry out density functional theory (DFT) calculations in order to investigate the temperature dependent reionization spectrum, i.e., the spectrum of the process. We find that simultaneous optical reionization and qubit manipulation can be carried out at room temperature with photoexcitation at the typical excitation wavelength used for readout of the divacancy qubits in 4H SiC, in agreement with our experimental data. We also provide the analysis of the PL spectrum of , characteristic for each configuration in 4H SiC, using the Huang-Rhys theory, and find that one configuration in 4H SiC stands out in terms of the strength of coherent emission among the four configurations.
|
|
| 5. |
- Csore, A., et al.
(författare)
-
Towards identification of silicon vacancy-related electron paramagnetic resonance centers in 4H-SiC
- 2021
-
Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 104:3
-
Tidskriftsartikel (refereegranskat)abstract
- The negatively charged silicon vacancy (V-Si(-)) in silicon carbide (SiC) is a paramagnetic and optically active defect in hexagonal SiC. The V(Si)(- )defect possesses S = 3/2 spin with long spin coherence time, and it can be optically manipulated even at room temperature. Recently, electron spin resonance signals have been observed besides those associated with the V-Si(- ) defects in the 4H polytype of SiC. The corresponding centers share properties akin to those of the V-Si(- ) defects and thus they may be promising candidates for quantum technology applications. However, the exact origin of the new signals is unknown. In this paper, we report V-1-related pair defect models as possible candidates for the unknown centers. We determine the corresponding electronic structures and magneto-optical properties as obtained by density functional theory calculations. We propose models for the recently observed electron paramagnetic resonance centers, and we predict their optical signals for identification in future experiments.
|
|
| 6. |
|
|
| 7. |
- Son Tien, Nguyen, et al.
(författare)
-
Defects at nitrogen site in electron-irradiated AlN
- 2011
-
Ingår i: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 98:24, s. 242116-
-
Tidskriftsartikel (refereegranskat)abstract
- In high resistance AlN irradiated with 2 MeV electrons, an electron paramagnetic resonance (EPR) spectrum, labeled EI-1, with an electron spin S=1/2 and a clear hyperfine (hf) structure was observed. The hf structure was shown to be due the interaction between the electron spin and the nuclear spins of four (27)A nuclei with the hf splitting varying between similar to 6.0 and similar to 7.2 mT. Comparing the hf data obtained from EPR and ab initio supercell calculations we suggest the EI-1 defect to be the best candidate for the neutral nitrogen vacancy in AlN.
|
|
| 8. |
- Spindlberger, L., et al.
(författare)
-
Optical Properties of Vanadium in 4H Silicon Carbide for Quantum Technology
- 2019
-
Ingår i: Physical Review Applied. - : AMER PHYSICAL SOC. - 2331-7019. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- We study the optical properties of tetravalent-vanadium impurities in 4H silicon carbide. Light emission from two crystalline sites is observed at wavelengths of 1.28 and 1.33 mu m, with optical lifetimes of 163 and 43 ns, respectively, which remains stable up to 50 and 20 K, respectively. Moreover, spectrally broad photoluminescence is observed up to room temperature. Group-theory and ab initio density-functional supercell calculations enable unequivocal site assignment and shed light on the spectral features of the defects. Specifically, our numerical simulations indicate that the site assignment is reversed with respect to previous assumptions. Our calculations show that vanadium in silicon carbide has highly favorable properties for the generation of single photons in the telecommunication wavelength regime. Combined with the available electronic and nuclear degrees of freedom, vanadium presents all the ingredients required for a highly efficient spin-photon interface.
|
|
| 9. |
- Szállás, A., et al.
(författare)
-
Characterization of the nitrogen split interstitial defect in wurtzite aluminum nitride using density functional theory
- 2014
-
Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 116:11, s. 113702-1-113702-5
-
Tidskriftsartikel (refereegranskat)abstract
- We carried out Heyd-Scuseria-Ernzerhof hybrid density functional theory plane wave supercell calculations in wurtzite aluminum nitride in order to characterize the geometry, formation energies, transition levels, and hyperfine tensors of the nitrogen split interstitial defect. The calculated hyperfine tensors may provide useful fingerprint of this defect for electron paramagnetic resonance measurement.
|
|
| 10. |
|
|
