Theoretical study of nitrogen-vacancy spin coherence enhanced by vacancy aggregation in diamond using cluster-correlation expansion
Abstract
Annealing a semiconductor makes its vacancies mobile; they aggregate into multi-vacancy complexes that often carry spin. Such centres are a magnetic-noise source for any spin qubit among them, in silicon and silicon carbide as well as in diamond, and they are accordingly blamed for NV- decoherence in irradiated and implanted diamond, with two coherence records credited to removing them. Cluster-correlation-expansion simulations driven by published electron-paramagnetic-resonance parameters invert that attribution. At a fixed paramagnetic spin density a multi-vacancy bath gives a Hahn-echo coherence time 3.1-7.1 times longer than a bath of isolated negative vacancies, over three decades of concentration. A bath dephases the qubit because its spins exchange spin projections with one another, and two can exchange only if their transition frequencies match. A fine-structure splitting shifts those frequencies. Were every defect on the same crystallographic site, all would shift alike and still match: worth only a factor 1.15. Real defects occupy symmetry-equivalent sites pointing in different directions, so neighbours land at different frequencies and stop exchanging: a further 2.7. What governs the coherence time is therefore the fraction of bath pairs sharing a transition frequency, not the zero-field splitting. Vacancy aggregation extends NV- spin coherence rather than shortening it.
Related
- Dynamical-mean-field cluster-correlation expansion of NV- spin-echo decoherence in a realistic substitutional-nitrogen bath
- Theoretical estimation of nonlinear response function and ultrafast optical spectroscopy of nitrogen vacancy centers
- Vacancy-mediated nitrogen diffusion and aggregation via high-fluence electron beam irradiation in HPHT synthesized diamond crystal
- Semiclassical spin-bath calculation of the nitrogen-isotope effect on NV- ensemble coherence in diamond
- Low-field dephasing time of an optically polarized NV- spin bath beyond the P1 limit in diamond: a cluster-correlation-expansion and exact spin-bath study
BibTeX
@misc{shinei2026theoretical,
title = {{Theoretical study of nitrogen-vacancy spin coherence enhanced by vacancy aggregation in diamond using cluster-correlation expansion}},
author = {Chikara Shinei},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.24295},
eprint = {2609.24295},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.24295},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Theoretical study of nitrogen-vacancy spin coherence enhanced by vacancy aggregation in diamond using cluster-correlation expansion
AU - Chikara Shinei
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2609.24295
UR - https://arxiv.org/abs/2609.24295
AB - Annealing a semiconductor makes its vacancies mobile; they aggregate into multi-vacancy complexes that often carry spin. Such centres are a magnetic-noise source for any spin qubit among them, in silicon and silicon carbide as well as in diamond, and they are accordingly blamed for NV- decoherence in irradiated and implanted diamond, with two coherence records credited to removing them. Cluster-correlation-expansion simulations driven by published electron-paramagnetic-resonance parameters invert that attribution. At a fixed paramagnetic spin density a multi-vacancy bath gives a Hahn-echo coherence time 3.1-7.1 times longer than a bath of isolated negative vacancies, over three decades of concentration. A bath dephases the qubit because its spins exchange spin projections with one another, and two can exchange only if their transition frequencies match. A fine-structure splitting shifts those frequencies. Were every defect on the same crystallographic site, all would shift alike and still match: worth only a factor 1.15. Real defects occupy symmetry-equivalent sites pointing in different directions, so neighbours land at different frequencies and stop exchanging: a further 2.7. What governs the coherence time is therefore the fraction of bath pairs sharing a transition frequency, not the zero-field splitting. Vacancy aggregation extends NV- spin coherence rather than shortening it.
ER -