Probing boron vacancy defects in hBN via single spin relaxometry

Nat. Commun. 17, 3718 (2026) · DOI: 10.1038/s41467-026-70545-6

License: CC BY 4.0.

Abstract

Spin defects in solids offer promising platforms for quantum sensing and memory due to their long coherence times and optical addressability. Here, we integrate a single nitrogen-vacancy (NV) center in diamond with scanning probe microscopy to detect, read out, and spatially map spin-based quantum sensors at the nanoscale. Using the boron vacancy ($\mathrm{V}_\mathrm{B}^-$) center in hexagonal boron nitride—an emerging two-dimensional spin system—as a model, we detect its electron spin resonance indirectly via changes in the spin relaxation time ($T_1$) of a nearby NV center, eliminating the need for optical excitation or fluorescence detection of the $\mathrm{V}_\mathrm{B}^-$. Cross-relaxation between NV and $\mathrm{V}_\mathrm{B}^-$ ensembles significantly reduces NV $T_1$, enabling quantitative nanoscale mapping of defect densities beyond the optical diffraction limit and clear resolution of hyperfine splitting in isotopically enriched h$^{10}$B$^{15}$N. Our method demonstrates interactions between spin sensors in 3D and 2D materials, establishing NV centers as versatile probes for characterizing otherwise inaccessible spin defects.

Figures

10 panels with data across 3 figures. Each panel page shows the plot, its columns and its files; each data.csv begins with a header naming the paper, the panel, the source, the license and the provenance route.

Fig. 1

• panel (b): Calculated spin resonance dispersions, Frequency (GHz) against Magnetic Field (G), with the field 29 degrees from the surface normal: NV $0 \leftrightarrow +1$ and $0 \leftrightarrow -1$, and the two $\mathrm{V_B^-}$ transitions, which the printed legend labels BV. The dotted vertical line marks the cross-relaxation crossing; the green dot of the printed panel is not drawn. data.csv
• panel (c): CW-ODMR spectra at the cross-relaxation condition, normalized PL against Frequency (GHz): NV only and NV on hBN$_\mathrm{nat}$ on the left axis, $\mathrm{V_B^-}$ in hBN$_\mathrm{nat}$ on the right axis, as printed. The curve is the Lorentzian fit to the $\mathrm{V_B^-}$ spectrum; the fits to the two NV spectra are not drawn. data.csv
• panel (d): NV spin $T_1$ measurement after engaging the hBN$_\mathrm{nat}$ sample: Normalized PL against Delay Time (ms), on a logarithmic axis, in the non-CR and CR conditions. The single-exponential fits of the printed panel are not drawn. data.csv

Fig. 2

• panel (a): CW-ODMR spectrum of $\mathrm{V_B^-}$ centers in h$^{10}$B$^{15}$N at an out-of-plane field of 123 G: PL (kcts/s) against Frequency (GHz), measured points with the four-Lorentzian fit. data.csv
• panel (b): Center Frequency (GHz) of the NV $0 \leftrightarrow +1$ and $\mathrm{V_B^-}$ $0 \leftrightarrow -1$ transitions against Magnetic Field (G): measured points with the solid straight-line fit to each branch, and the four calculated hyperfine line positions $m_I = -3/2$, $-1/2$, $+1/2$ and $+3/2$ (dotted). data.csv
• panel (c): Single-$\tau$ $T_1$-MR scan of h$^{10}$B$^{15}$N at $\tau = 2$ ms: PL (counts) against detuning $(\omega_\mathrm{NV} - \omega_{\mathrm{V_B^-}})/A_{zz}$, with shot-noise error bars and the four-Lorentzian fit. The printed panel shows normalized PL; this one shows raw counts. data.csv
• panel (d): Single-$\tau$ $T_1$-MR scan of hBN$_\mathrm{nat}$ at $\tau = 0.7$ ms: Normalized PL against detuning $(\omega_\mathrm{NV} - \omega_{\mathrm{V_B^-}})/A_{zz}$, with error bars for the normalized shot noise and the Lorentzian fit. data.csv
• panel (e): Spin $T_1$ relaxation curve of a short-$T_1$ NV tip before engaging the sample: PL (counts) against Delay Time ($\mu$s), on a logarithmic axis, with the single-exponential fit. The printed panel shows normalized PL; this one shows raw counts. data.csv
• panel (f): NV $T_1$ ($\mu$s) against detuning $(\omega_\mathrm{NV} - \omega_{\mathrm{V_B^-}})/A_{zz}$, with error bars for the $1\sigma$ uncertainty of each $T_1$ value, and the four-Lorentzian fit. data.csv

Fig. 3

• panel (e): Monte Carlo simulation of the cross-relaxation rate $\Gamma_1^{\mathrm{CR}}$ (kHz) against $\mathrm{V_B^-}$ Density (ppm), on log-log axes, for three NV-to-sample distances: 6.9, 11.4 and 15.9 nm. The horizontal bar of the printed panel, marking the range of the colour scale in panel (f), is not drawn. data.csv

Cite

Alex L. Melendez et al. (17 authors). Probing boron vacancy defects in hBN via single spin relaxometry. Nat. Commun. 17, 3718 (2026). https://doi.org/10.1038/s41467-026-70545-6

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