发表机构
University of Tsukuba; CNRS, University Grenoble Alpes, Grenoble INP, University of Tsukuba（筑波大学; 法国国家科学研究中心，格勒诺布尔阿尔卑斯大学，格勒诺布尔理工学院，筑波大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过半经典自旋浴模型，研究氮同位素对NV$^-$系综相干性的影响，发现$^{15}$N使$T_2$缩短而$T_2^*$不变，比值$T_2$($^{14}$N)/$T_2$($^{15}$N) = 1.118，解释了实验观测的部分差异。
AI 中文摘要
氮空位（NV$^-$）系综的Hahn回波时间$T_2$与Ramsey时间$T_2^*$之比与氮浓度[N]无关，在天然同位素丰度（$^{14}$N）金刚石中约为16，但最近一个$^{15}$N掺杂系综磁力计在单量子约定下仅给出8.05 ± 0.18。我们探究氮核同位素本身是否足以导致这种降低。利用包含Jahn-Teller分辨的P1超精细张量的半经典自旋浴模型，我们证明对于$^{14}$N（I = 1），超精细简并因而可自由翻转的P1对比例为1/4，而对于$^{15}$N（I = 1/2），该比例为5/16。在[N] = 0.1–100 ppm范围内的模拟证实，这缩短了$T_2$而$T_2^*$完全不变：$T_2$($^{14}$N)/$T_2$($^{15}$N) = 1.118 ± 0.011，与[N]无关且高于1达11$\sigma$。测量的对比度为2.07 ± 0.25，高出3.8$\sigma$，表明共振通道计数是真实但部分的贡献，并为多体计算设定了定量基准。
英文摘要
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 $\approx$ 16 in diamond of natural isotopic abundance ($^{14}$N), yet a recent $^{15}$N-doped ensemble magnetometer gives only 8.05 $\pm$ 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 $^{14}$N (I = 1) but 5/16 for $^{15}$N (I = 1/2). Simulations over [N] = 0.1--100 ppm confirm that this shortens $T_2$ while leaving $T_2^*$ exactly unchanged: $T_2$($^{14}$N)/$T_2$($^{15}$N) = 1.118 $\pm$ 0.011, independent of [N] and 11$σ$ above unity. The measured contrast, 2.07 $\pm$ 0.25, is 3.8$σ$ larger, identifying resonant-channel counting as a real but partial contribution and setting a quantitative benchmark for many-body calculations.
Comments5 pages, 3 figures, 1 table; Supplementary Material (6 pages, 2 figures, 1 table) included
