Semiclassical spin-bath calculation of the nitrogen-isotope effect on NV- ensemble coherence in diamond
Abstract
The ratio T2/T2* of the Hahn-echo and Ramsey times of nitrogen-vacancy (NV-) ensembles is independent of the nitrogen concentration [N] and is ≈ 16 in diamond of natural isotopic abundance (14N), yet a recent 15N-doped ensemble magnetometer gives only 8.05 ± 0.18 in the single-quantum convention. We ask whether the nitrogen nuclear isotope alone can cause such a reduction. Using a semiclassical spin-bath model with the Jahn-Teller-resolved P1 hyperfine tensor, we show that the fraction of P1 pairs that are hyperfine-degenerate, and hence free to flip-flop, is 1/4 for 14N (I = 1) but 5/16 for 15N (I = 1/2). Simulations over [N] = 0.1--100 ppm confirm that this shortens T2 while leaving T2* exactly unchanged: T2(14N)/T2(15N) = 1.118 ± 0.011, independent of [N] and 11σ above unity. The measured contrast, 2.07 ± 0.25, is 3.8σ larger, identifying resonant-channel counting as a real but partial contribution and setting a quantitative benchmark for many-body calculations.
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BibTeX
@misc{shinei2026semiclassical,
title = {{Semiclassical spin-bath calculation of the nitrogen-isotope effect on NV$^-$ ensemble coherence in diamond}},
author = {Chikara Shinei},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37596},
eprint = {2609.37596},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37596},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Semiclassical spin-bath calculation of the nitrogen-isotope effect on NV^- ensemble coherence in diamond
AU - Chikara Shinei
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2609.37596
UR - https://arxiv.org/abs/2609.37596
AB - The ratio T_2/T_2^* of the Hahn-echo and Ramsey times of nitrogen-vacancy (NV^-) ensembles is independent of the nitrogen concentration [N] and is ≈ 16 in diamond of natural isotopic abundance (^14N), yet a recent ^15N-doped ensemble magnetometer gives only 8.05 ± 0.18 in the single-quantum convention. We ask whether the nitrogen nuclear isotope alone can cause such a reduction. Using a semiclassical spin-bath model with the Jahn-Teller-resolved P1 hyperfine tensor, we show that the fraction of P1 pairs that are hyperfine-degenerate, and hence free to flip-flop, is 1/4 for ^14N (I = 1) but 5/16 for ^15N (I = 1/2). Simulations over [N] = 0.1--100 ppm confirm that this shortens T_2 while leaving T_2^* exactly unchanged: T_2(^14N)/T_2(^15N) = 1.118 ± 0.011, independent of [N] and 11σ above unity. The measured contrast, 2.07 ± 0.25, is 3.8σ larger, identifying resonant-channel counting as a real but partial contribution and setting a quantitative benchmark for many-body calculations.
ER -