Investigation of dynamic nuclear polarization with boron vacancy defects in hexagonal boron nitride
Kento Sasaki
The University of Tokyo – Tokyo Japan
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Boron vacancy defects (VB) in hexagonal boron nitride (hBN) are luminescent defects exhibit optically detected magnetic resonance (ODMR) at room temperature and are being researched for use in quantum technologies. The electron spins of VB interacting with the nuclear spins of nitrogen and boron allow their dynamic nuclear polarization (DNP) and coherent manipulation. However, the behavior of such multiple-spin system is inherently complex. For understanding, it is useful to build physical model [1] based on systematic investigations using simplified systems with isotopic enrichment [2]. In this study, we precisely measure the ODMR spectra of VB in h10B15N over a wide magnetic field range (10~150 mT), including DNP conditions near level anti-crossing (LAC), and compare them with the simulations of the time dependent Lindblad equation [3]. Our simulation that considers a single electron spin and three neighboring 15N nuclear spins successfully reproduces the experimental ODMR spectra, including the vicinity of LAC. It can explain the overall behavior of the magnetic field dependence of the nuclear spin polarization estimated using the Lorentzian fitting of the spectra. Despite such qualitative agreement, we also demonstrate that the conventional fitting methods cannot give true nuclear polarizations. We also discuss that mechanisms related with defect symmetry limit the maximum polarization. Our study is an important step toward a quantitative understanding of multiple-spin system in hBN and its quantum applications.
References
1. S. Ru, Z. Jiang, H. Liang, J. Kenny, H. Cai, X. Lyu, R. Cernansky, F. Zhou, Y. Yang, K. Watanabe, T. Taniguch, F. Li, T. S. Koh, X. Liu, F. Jelezko, A. A. Bettiol, and W. Gao, ‘Robust nuclear spin polarization via ground-state level anticrossing of boron vacancy defects in hexagonal boron nitride’, Phys. Rev. Lett. 132, 266801 (2024).
2. K. Sasaki, T. Taniguchi, and K. Kobayashi, ‘Nitrogen isotope effects on boron vacancy quantum sensors in hexagonal boron nitride’, Appl. Phys. Express 16, 095003 (2023).
3. Y. Nakamura, S. Nishimura, T. Iwasaki, S. Nakaharai, S. Og