2025-05-16 京都大学
（左）ダイヤモンドのNV中心の電子スピン（オレンジ色の矢印）は、磁場に対して非常に敏感である一方、窒素の核スピン（マゼンタ色の矢印）は低い磁気回転比のため、磁場に対してそれほど敏感ではない。（右）しかし、暗黒物質のアクシオン場の勾配との結合にはそのような制限がないため、核スピンは長いコヒーレンス時間を利用してこの暗黒物質候補を高感度に検出することが期待できる。
＜関連情報＞
- https://www.kyoto-u.ac.jp/ja/research-news/2025-05-16
- https://www.kyoto-u.ac.jp/sites/default/files/2025-05/web_2505_Mizuochi-82dd245eede7a9a81aa2ac58477ba8bf.pdf
- https://journals.aps.org/prd/abstract/10.1103/PhysRevD.111.075028
アクシオン暗黒物質検出のためのダイヤモンドの窒素空孔中心を用いた核スピン計測 Nuclear spin metrology with nitrogen vacancy center in diamond for axion dark matter detection
So Chigusa, Masashi Hazumi, Ernst David Herbschleb, Yuichiro Matsuzaki, Norikazu Mizuochi, and Kazunori Nakayama
Physical Review D Published: 29 April, 2025
DOI: https://doi.org/10.1103/PhysRevD.111.075028
Abstract
We present a method to directly detect the axion dark matter using nitrogen vacancy centers in diamonds. In particular, we use metrology leveraging the nuclear spin of nitrogen to detect axion-nucleus couplings. This is achieved through protocols designed for dark matter searches, which introduce a novel approach of quantum sensing techniques based on the nitrogen vacancy center. Although the coupling strength of the magnetic fields with nuclear spins is three orders of magnitude smaller than that with electron spins for conventional magnetometry, the axion interaction strength with nuclear spins is the same order of magnitude as that with electron spins. Furthermore, we can take advantage of the long coherence time by using the nuclear spins for the axion dark matter detection. Our method has the potential to be sensitive to a broad frequency range ≲100 Hz corresponding to the axion mass ≲4×10−13 eV. We present the detection limit of our method for both the axion-neutron and the axion-proton couplings and discuss its significance in comparison with other proposed ideas. We also show that the sensitivities of the NV center sensor to various spin species will open up new directions for constructing protocols that can mitigate magnetic noise effects.
