Landau-Zener interaction enhanced quantum sensitivity in spin defects of hexagonal boron nitride

Negatively charged boron vacancy (V_B–) in hexagonal boron nitride (hBN) offer promise in quantum sensing as they are optically addressable at room temperature and can be transferred on 2D materials. However, their broad hyperfine-split spin transitions pose challenges for sensitivity to fluctuating magnetic fields with conventional resonant excitation. While isotopically enriched h¹⁰B¹⁵N exhibits sharper spectral features due to reduced hyperfine splitting, significant broadening remains. We demonstrate that frequency-ramped Landau-Zener sweeps mitigates this by driving population transfer across the inhomogeneously broadened spectrum. Using IQ modulation on an FPGA RFSoC 4x2, we implement frequency sweeps producing Landau-Zener transitions between the 0 and -1 spin states. After sweep rate optimization, we achieve 4.5 times greater spin inversion compared to resonant excitation, enabling a 20-fold reduction in measurement time for equivalent signal-to-noise ratio. We model the dynamics using QuTiP, showing that an effective two-state model captures the behavior despite spectral complexity. We investigate multiple consecutive sweeps as well. This approach demonstrates a practical pathway to enhance T1 sensing with V_B– in hBN.