空位聚集增强金刚石中NV-自旋相干性：半导体多空位自旋浴的团簇关联展开研究

中文摘要 AI 辅助

退火使半导体中的空位变得可移动；它们聚集成多空位复合体，这些复合体通常携带自旋。此类中心是硅、碳化硅以及金刚石中任何自旋量子比特的磁噪声源，因此它们被归咎于辐照和注入金刚石中NV-退相干的原因，两项相干性记录也归功于去除它们。由已发表的电子顺磁共振参数驱动的团簇关联展开模拟推翻了这一归因。在固定的顺磁自旋密度下，多空位浴给出的Hahn回波相干时间比孤立负空位浴长2.7-4.4倍，且在三个数量级的浓度范围内保持恒定。浴使量子比特退相干是因为其自旋相互交换自旋投影，而两个自旋只有在跃迁频率匹配时才能交换。精细结构分裂会移动这些频率。如果每个缺陷都位于相同的晶体学位置，则所有缺陷的移动相同且仍能匹配：仅带来1.3倍的改善。实际缺陷占据指向不同方向的对称等效位置，因此相邻缺陷处于不同频率并停止交换：再带来1.9倍的改善。因此，决定相干时间的是共享跃迁频率的浴对比例，而非零场分裂。空位聚集延长而非缩短NV-自旋相干性。

英文摘要

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.

发表机构

• University of Tsukuba（筑波大学）
• Institute of Pure and Applied Sciences（纯理与应用科学研究院）
• Japanese-French Laboratory for Semiconductor Physics and Technology J-FAST（日法半导体物理与技术实验室（J-FAST））
• CNRS（法国国家科学研究中心）
• University Grenoble Alpes（格勒诺布尔阿尔卑斯大学）
• Grenoble INP（格勒诺布尔国立理工学院）

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