Optically active point defects in semiconductors have received great attention in the field of solid-state quantum technologies. Hexagonal boron nitride, with an ultra-wide band gapEg= 6 eV, containing a negatively charged boron vacancy (VB-) with unique spin, optical, and coherent properties presents a new two-dimensional platform for the implementation of quantum technologies. This work establishes the value ofVB-spin polarization under optical pumping withλext= 532 nm laser using high-frequency (νmw= 94 GHz) electron paramagnetic resonance (EPR) spectroscopy. In optimal conditions polarization was found to beP≈ 38.4%. Our study reveals that Rabi oscillations induced on polarized spin states persist for up to 30-40μs, which is nearly two orders of magnitude longer than what was previously reported. Analysis of the coherent electron-nuclear interaction through the observed electron spin echo envelope modulation made it possible to detect signals from remote nitrogen and boron nuclei, and to establish a corresponding quadrupole coupling constantCq= 180 kHz related to nuclear quadrupole moment of14N. These results have fundamental importance for understanding the spin properties of boron vacancy.
Keywords: Rabi oscillations; boron vacancy; color center; electron paramagnetic resonance; hBN; optical spin polarization; van der Waals materials.
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