Designing defect-based qubit candidates in wide-gap binary semiconductors for solid-state quantum technologies

Seo, Hosung; Ma, He; Govoni, Marco; Galli, Giulia

doi:10.1103/physrevmaterials.1.075002

Cited by 59 publications

(66 citation statements)

References 78 publications

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“…This surprisingly good results must be a consequence of error cancellations in these calculations. 123 Note also that the current implementations may not be suitable for defects with S2, where higher order terms are expected (see Table 3), and when the g-tensor deviates considerably from g e I of the free electron. 116 ZFS of point defect qubits is a key quantity to measure variations of the external degrees of freedom.…”

Section: G-tensormentioning

confidence: 95%

“…In the latter publication an efficient implementation was presented for the plane wave basis set, which was later utilized in other publications too. 122,123 In all of these early implementations pseudopotentials and pseudowavefunctions were used. The theory of Rayson et al was recently extended to the PAW method to include corrections from the core region.…”

Section: G-tensormentioning

confidence: 99%

“…116 ZFS of point defect qubits is a key quantity to measure variations of the external degrees of freedom. Recently, pressure, 122,123 strain, 126 electric field, 127 and temperature dependence 122 of the ZFS were successfully studied by first principles calculations.…”

Section: G-tensormentioning

confidence: 99%

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First principles calculation of spin-related quantities for point defect qubit research

2018

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Point defect research in semiconductors has gained remarkable new momentum due to the identification of special point defects that can implement qubits and single photon emitters with unique characteristics. Indeed, these implementations are among the few alternatives for quantum technologies that may operate even at room temperature, and therefore discoveries and characterization of novel point defects may highly facilitate future solid state quantum technologies. First principles calculations play an important role in point defect research, since they provide a direct, extended insight into the formation of the defect states. In the last decades, considerable efforts have been made to calculate spin-dependent properties of point defects from first principles. The developed methods have already demonstrated their essential role in quantitative understanding of the physics and application of point defect qubits. Here, we review and discuss accuracy aspects of these novel ab initio methods and report on their most relevant applications for existing point defect qubits in semiconductors. We pay attention to the advantages and limitations of the methodological solutions and highlight additional developments that are expected in the near future. Moreover, we discuss the opportunity of a systematic search for potential point defect qubits, as well as the possible development of predictive spin dynamic simulations facilitated by ab initio calculations of spin-dependent quantities.npj Computational Materials (2018) 4:76 ; https://doi.

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Section: G-tensormentioning

confidence: 95%

Section: G-tensormentioning

confidence: 99%

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First principles calculation of spin-related quantities for point defect qubit research

2018

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“…Previously, the idea to treat the ZFS tensor within the pseudopotential plane-wave framework was formulated by Rayson and Briddon [16] and revisited by Bodrog and Gali [17]. The potential capabilities of the complete PAW treatment were further addressed in the literature [11,18], but a detailed evaluation of the reconstruction scheme and a comparison with all-electron data are still missing. Even though it was possible to obtain satisfying results for some point defects by considering only smooth pseudowave functions [11], the potential significance of the on-site reconstruction of all-electron wave functions has been pointed out recently in the literature [18].…”

Section: Introductionmentioning

confidence: 99%

Calculation of spin-spin zero-field splitting within periodic boundary conditions: Towards all-electron accuracy

2018

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For high-spin centers, one of the key spectroscopic fingerprints is the zero-field splitting (ZFS) addressable by electron paramagnetic resonance. In this paper, an implementation of the spin-spin contribution to the ZFS tensor within the projector augmented-wave (PAW) formalism is reported. We use a single-determinant approach proposed by M. J. Rayson and P. R. Briddon [Phys. Rev. B 77, 035119 (2008)], and complete it by adding a PAW reconstruction term which has not been taken into account before. We benchmark the PAW approach against a well-established all-electron method for a series of diatomic radicals and defects in diamond and cubic silicon carbide. While for some of the defect centers the PAW reconstruction is found to be almost negligible, in agreement with the common assumption, we show that in general it significantly improves the calculated ZFS towards the all-electron results.

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“…Since its development, PyZFS has been adopted to predict ZFS tensors for spin defects in semiconductors, and facilitated the discovery of novel spin defects (Seo, Ma, Govoni, & Galli, 2017) and the study of spin-phonon interactions in solids (Whiteley et al, 2019). PyZFS has also been adopted to generate benchmark data for the development of methods to compute the ZFS tensor using all electron calculations on finite element basis sets (Ghosh, Ma, Gavini, & Galli, 2019).…”

Section: Discussionmentioning

confidence: 99%

PyZFS: A Python package for first-principles calculations of zero-field splitting tensors

Ma¹,

Govoni²,

Galli³

2020

JOSS

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Electron spins in molecules and materials may be manipulated and used to store information, and hence they are interesting resources for quantum technologies. A way to understand the physical properties of electron spins is to probe their interactions with electromagnetic fields. Such interactions can be described by using a so-called spin Hamiltonian, with parameters derived from either experiments or calculations. For a single electron spin (e.g., associated to a point-defect in a semiconductor or insulator), the leading terms in the spin Hamiltonian arewhere µ B is the Bohr magneton, S is the electron spin operator, B is an external magnetic field, g and D are rank-2 tensors that characterize the strength of the Zeeman interaction, and the zero-field splitting (ZFS), respectively. Experimentally, the spin Hamiltonian parameters g and D may be obtained by electron paramagnetic resonance (EPR). The ZFS tensor describes the lifting of degeneracy of spin sublevels in the absence of external magnetic fields, and is an important property of open-shell molecules and spin defects in semiconductors with spin quantum number S ≥ 1. The ZFS tensor can be predicted from first-principles calculations, thus complementing experiments and providing valuable insight into the design of novel molecules and materials with desired spin properties. Furthermore, the comparison of computed and measured ZFS tensors may provide important information on the atomistic structure and charge state of defects in solids, thus helping to identify the defect configuration present in experimental samples. Therefore, the development of robust methods for the calculation of the ZFS tensor is an interesting topic in molecular chemistry and materials science.In this work we describe the code PyZFS for the calculation of the ZFS tensor D of molecules and solids, based on wavefunctions obtained from density functional theory (DFT) calculations. For systems without heavy elements, i.e., where spin-orbit coupling is negligible, magnetic spinspin interactions are the dominant ones in the determination of the ZFS tensor. For molecules and materials with magnetic permeability close to the vacuum permeability µ 0 , the spin-spin ZFS tensor evaluated using the DFT Kohn-Sham wavefunctions, is given by Harriman (1978):where a, b = x, y, z are Cartesian indices; γ e is the gyromagnetic ratio of electrons; the summation runs over all pairs of occupied Kohn-Sham orbitals; χ ij = ±1 for parallel and antiparallel spins, respectively; Φ ij (r, r ′ ) are 2 × 2 determinants formed from Kohn-Sham orbitals ϕ i and ϕ j , Φ ij (r, r ′ ) = 1 √ 2 [ ϕ i (r)ϕ j (r ′ ) − ϕ i (r ′ )ϕ j (r)].Ma et al., (2020). PyZFS: A Python package for first-principles calculations of zero-field splitting tensors.

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Designing defect-based qubit candidates in wide-gap binary semiconductors for solid-state quantum technologies

Cited by 59 publications

References 78 publications

First principles calculation of spin-related quantities for point defect qubit research

First principles calculation of spin-related quantities for point defect qubit research

Calculation of spin-spin zero-field splitting within periodic boundary conditions: Towards all-electron accuracy

PyZFS: A Python package for first-principles calculations of zero-field splitting tensors

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