First Principles Identification of Divacancy Related Photoluminescence Lines in 4H and 6H-SiC

2016 ◽  
Vol 858 ◽  
pp. 322-325 ◽  
Author(s):  
Viktor Ivády ◽  
Krisztián Szász ◽  
Abram L. Falk ◽  
Paul V. Klimov ◽  
Erik Janzén ◽  
...  
Keyword(s):  
Point Defects ◽  
First Principles ◽  
Large Scale ◽  
Computational Techniques ◽  
Zero Field ◽  
Electron Configuration ◽  
Zero Field Splitting ◽  
Quantum Bit ◽  
Related Point ◽  
Previous Assignment

Nowadays, computational techniques can greatly facilitate the identification of point defect related photoluminescence and EPR centers in semiconductors. Once the identification has been achieved, one can gain a detailed description of the microstructure and the electron configuration of the defect, providing a basis for further understanding and development. Recently, the importance of divacancy and related point defects in different polytypes of SiC has substantially increased due to their possible quantum bit application. However, their different configurations have not been satisfactorily identified yet. In our study, we carry out large-scale first principles supercell calculations to identify the divacancy related point defects in 4H and 6H-SiC. By resolving some general accuracy issues of usual ab initio supercell techniques, we are able to obtain convergent photoluminescence (PL) energies, zero-field-splitting, and hyperfine parameters. Our results confirm the previous assignment of the PL1-4 PL lines in 4H-SiC (also known as UD-2 luminescence lines previously) to the four possible divacancy configurations and provide the identification of QL1,QL2, and QL6 PL lines in 6H-SiC. In all cases the calculated zero-field and hyperfine tensors’ parameters are provided.

scholarly journals Readout and control of an endofullerene electronic spin

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Dinesh Pinto ◽  
Domenico Paone ◽  
Bastian Kern ◽  
Tim Dierker ◽  
René Wieczorek ◽  
...  
Keyword(s):  
Self Assembly ◽  
Large Scale ◽  
Dipolar Interaction ◽  
Nitrogen Vacancy ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Paramagnetic Resonance ◽  
Near Surface ◽  
Atomic Spins ◽  
And Control

AbstractAtomic spins for quantum technologies need to be individually addressed and positioned with nanoscale precision. C60 fullerene cages offer a robust packaging for atomic spins, while allowing in-situ physical positioning at the nanoscale. However, achieving single-spin level readout and control of endofullerenes has so far remained elusive. In this work, we demonstrate electron paramagnetic resonance on an encapsulated nitrogen spin (14N@C60) within a C60 matrix using a single near-surface nitrogen vacancy (NV) center in diamond at 4.7 K. Exploiting the strong magnetic dipolar interaction between the NV and endofullerene electronic spins, we demonstrate radio-frequency pulse controlled Rabi oscillations and measure spin-echos on an encapsulated spin. Modeling the results using second-order perturbation theory reveals an enhanced hyperfine interaction and zero-field splitting, possibly caused by surface adsorption on diamond. These results demonstrate the first step towards controlling single endofullerenes, and possibly building large-scale endofullerene quantum machines, which can be scaled using standard positioning or self-assembly methods.

scholarly journals First-Principles Investigations of Magnetic Anisotropy and Spin-Crossover Behavior of Fe(III)-TBP Complexes

2020 ◽  
Author(s):  
Rishu Khurana ◽  
Sameer Gupta ◽  
Md. Ehesan Ali
Keyword(s):  
Single Molecule ◽  
First Principles ◽  
Density Functional ◽  
Spin Crossover ◽  
Zero Field ◽  
Spin States ◽  
Zero Field Splitting ◽  
Field Splitting ◽  
B3lyp Functional ◽  
D Values

<div>With the ongoing efforts to obtain mononuclear 3d-transition metal complexes that manifest slow relaxation of magnetization and hence, can behave as single molecule magnets (SMMs), we have modelled 14 novel Fe(III) complexes out of which nine behave as potential SMMs. These complexes possess large zero-field splitting (ZFS)</div><div>parameter D in the range of -40 to -60 cm<sup>-1</sup>. The first-principles investigation of the ground-spin state applying density functional theory (DFT) and wave-function based</div><div>multi-configurations methods e.g. SA-CASSCF/NEVPT2 are found to be quite consistent except for few delicate cases with near degenerate spin-states. In such cases, the</div><div>hybrid B3LYP functional is found to be biased towards high-spin (HS) state. Altering the percentage of exact exchange admixed in B3LYP functional leads to intermediate spin</div><div>(IS) ground state consistent with the multireference calculations. The origin of large zero field splitting (ZFS) in the Fe(III)-based trigonal bipyramidal (TBP) complexes</div><div>is investigated and the D-values are further tuned by varying the axial ligands with group XV elements (N, P and As) and equatorial halide ligands from F, Cl, Br and I. Furthermore, a number of complexes are identified with very small Gibbs free energy values indicating the possible spin-crossover phenomenon between the bi-stable spin-states.</div>

scholarly journals First-principles calculations of iodine-related point defects in CsPbI3

2019 ◽  
Vol 21 (15) ◽  
pp. 7841-7846 ◽  
Author(s):  
Robert A. Evarestov ◽  
Alessandro Senocrate ◽  
Eugene A. Kotomin ◽  
Joachim Maier
Keyword(s):  
Electronic Structure ◽  
Point Defects ◽  
First Principles ◽  
First Principles Calculations ◽  
Hybrid Functional ◽  
Photovoltaic Applications ◽  
Related Point ◽  
Atomic And Electronic Structure

We present here first principles hybrid functional calculations of the atomic and electronic structure of several iodine-related point defects in CsPbI3, a material relevant for photovoltaic applications.

First-Principles Calculations of Point Defects for Quantum Technologies

2018 ◽  
Vol 48 (1) ◽  
pp. 1-26 ◽  
Author(s):  
Cyrus E. Dreyer ◽  
Audrius Alkauskas ◽  
John L. Lyons ◽  
Anderson Janotti ◽  
Chris G. Van de Walle
Keyword(s):  
Point Defects ◽  
First Principles ◽  
Optical Manipulation ◽  
Computational Techniques ◽  
First Principles Calculations ◽  
Exciting System ◽  
Optical And Magnetic Properties ◽  
Environmental Isolation ◽  
Defects In Semiconductors ◽  
Further Development

Point defects in semiconductors and insulators form an exciting system for realizing quantum technologies, including quantum computing, communication, and metrology. Defects provide a platform that combines the environmental isolation necessary to maintain the coherence of quantum states with the ability to perform electrical and optical manipulation. First-principles calculations play a crucial role in identifying, characterizing, and developing defects for quantum applications. We review the first-principles methodologies for calculating the relevant structural, electronic, vibrational, optical, and magnetic properties of defects for quantum technologies. We illustrate the utility and accuracy of these techniques by using examples from the literature. We also point out areas in which further development of the computational techniques is desirable.

First Principles Investigation of Divacancy in SiC Polytypes for Solid State Qubit Application

2014 ◽  
Vol 778-780 ◽  
pp. 499-502 ◽  
Author(s):  
Krisztián Szász ◽  
Viktor Ivády ◽  
Erik Janzén ◽  
Ádám Gali
Keyword(s):  
Density Functional Theory ◽  
Excited States ◽  
Ground State ◽  
First Principles ◽  
Density Functional ◽  
Zero Field ◽  
Polarization Phenomenon ◽  
Zero Field Splitting ◽  
Nuclear Spin Polarization ◽  
Functional Theory

We calculated the hyperfine structure and the zero-field splitting parameters of divacancies in 3C, 4Hand 6HSiC in the ground state and in the excited state for 4HSiC within the framework of density functional theory. Besides that our calculations provide identification of the defect in different polytypes, we can find some carbon atoms next to the divacancy that of the spin polarizations are similar in the ground and excited states. This coherent nuclear spin polarization phenomenon can be the base to utilize13C spins as quantum memory.

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