Electron-Nuclear Coherent Coupling and Nuclear Spin Readout through Optically Polarized VB- Spin States in hBN.

Coherent coupling of defect spins with surrounding nuclei along with the endowment to read out the latter are basic requirements for an application in quantum technologies. We show that negatively charged boron vacancies (VB-) in hexagonal boron nitride (hBN) meet these prerequisites. We demonstrate Hahn-echo coherence of the VB- spin with a characteristic decay time Tcoh = 15 µs, close to the theoretically predicted limit of 18 µs for defects in hBN. Elongation of the coherence time up to 36 µs is demonstrated by means of the Carr-Purcell-Meiboom-Gill decoupling technique. Modulation of the Hahn-echo decay is shown to be induced by coherent coupling of the VB- spin with the three nearest 14N nuclei via a nuclear quadrupole interaction of 2.11 MHz. DFT calculation confirms that the electron-nuclear coupling is confined to the defective layer and stays almost unchanged with a transition from the bulk to the single layer.

Study of Electron-Nuclear Interactions in Doped Calcium Phosphates by Various Pulsed EPR Spectroscopy Techniques.

Substituted calcium phosphates (CaPs) are vital materials for the treatment of bone diseases and repairing and replacement of defects in human hard tissues. In this paper, we present some applications of the rarely used pulsed electron paramagnetic resonance (EPR) and hyperfine interaction spectroscopy approaches [namely, electron spin-echo envelope modulation (ESEEM) and electron-electron double-resonance detected nuclear magnetic resonance (EDNMR)] to investigate synthetic CaPs (hydroxyapatite, tricalcium, and octacalcium phosphate) doped with various cations (Li+, Na+, Mn2+, Cu2+, Fe3+, and Ba2+). These resonance techniques provide reliable tools to obtain unique information about the presence and localization of impurity centers and values of hyperfine and quadrupole tensors. We show that revealed in CaPs by EPR techniques, radiation-induced stable nitrogen-containing species and carbonate radicals can serve as sensitive paramagnetic probes to follow CaPs' structural changes caused by cation doping. The most pulsed EPR, ESEEM, and EDNMR spectra can be detected at room temperature, reducing the costs of the measurements and facilitating the usage of pulsed EPR techniques for CaP characterization.