Exploring the properties of the V_B^- defect in hBN: optical spin polarization, Rabi oscillations, and coherent nuclei modulation

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 gap E-g = 6 eV, containing a negatively charged boron vacancy ( V-B(-) ) with unique spin, optical, and coherent properties presents a new two-dimensional platform for the implementation of quantum technologies. This work establishes the value of V-B(-) spin polarization under optical pumping with lambda( ext) = 532 nm laser using high-frequency (nu (mw) = 94 GHz) electron paramagnetic resonance (EPR) spectroscopy. In optimal conditions polarization was found to be P approximate to 38.4%. Our study reveals that Rabi oscillations induced on polarized spin states persist for up to 30-40 mu s, 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 constant C (q) = 180 kHz related to nuclear quadrupole moment of N-14. These results have fundamental importance for understanding the spin properties of boron vacancy.