High-Sensitivity Optical Detection of Electron-Nuclear Spin Clusters in Diamond

TL;DR

The study demonstrates high-sensitivity, room-temperature NMR of nuclear spin ensembles in diamond by optically detecting nuclear spins via NV centers near ESLAC. It maps multiple nuclear species ($^{13}$C and $^{14}$N) and their hyperfine tensors across NV electronic states, and introduces two-tone correlation spectroscopy to resolve degenerate sites and lift degeneracy with transverse fields. The work shows coherent control and Ramsey-based readout of $^{13}$C spins in the NV ground state, alongside evidence for NV-mediated coupling between 13C pairs, illustrating scalable pathways for polarization transfer, quantum metrology, and gyroscopic sensing using diamond-based spin ensembles. These findings broaden the applicability of ODNMR for bulk, ensemble-level nuclear-spin polarization and control at ambient conditions, potentially enabling practical quantum sensors and compact NMR-like devices. The results also set the stage for leveraging enriched $^{13}$C samples to boost signal and performance in diamond quantum technologies.

Abstract

We perform sensitive nuclear magnetic resonance (NMR) with spin ensembles which are polarized by nitrogen vacancy centers (NV centers) in diamond at room-temperature. With a near shot-noise-limited photoluminescence detection and a highly uniform magnetic field, we resolve sharp NMR features arising from multiple spin clusters. In particular, we investigate the coupling between nuclear spins and NV centers in the neutral and negatively charged states. Further, we perform high precision NMR and coherent control of families of carbon 13 nuclear spin ensembles in the $m_s$=0 level of the NV ground state. Applying an off-axis magnetic field reveals the various sites associated with the otherwise degenerate couplings of the carbon 13 sites around the NV electronic spin providing access to all the hyperfine tensor components. Last, we observe spectroscopic signatures of pairs of nuclear spins coupled to the same NV center. These results are relevant for ensemble measurements of dynamical polarization that currently rely on expensive nuclear magnetic resonance systems as well as for recently proposed nuclear spin gyroscopes.

Figures (10)

• Figure 1: a) Schematics showing the repartition of $^{13}$C atoms around the NV centers projected on a plane perpendicular to the NV axis. Families are defined according to their symmetries with respect to the NV axis, following the notation introduced in Smeltzer_njp. $\phi$ defines the angle between ${\bm B}_\perp$ and the axis $^{13}$C-NV. b) Schematics showing the $^{13}$C families projected on a plane containing the NV axis. $\theta$ defines the angle between the perpendicular plane passing though the vacancy and $^{13}$C families location.
• Figure 2: a) Optically detected magnetic resonance (ODMR) spectrum around the $\ket{0_e}\rightarrow\ket{-1_e}$ transition at B= 487 G. Blue points are experimental data, red line is a Lorentzian fit to the resonance associated with the $\ket{0_e, 1_N}\rightarrow \ket{-1_e, 1_N}$ transition. Electronic spin transitions associated with the NV electron coupled to the A, B, C and D $^{13}$C nuclear spin families are indicated by vertical lines. b) Electron spin echo signal subtracted from the slowly varying envelope (see main text). Insets: Spin echo sequence and Fourier transform of the spin echo curve.
• Figure 3: a) Optically Detected Nuclear Magnetic Resonance (ODNMR) spectrum at B= 486.8 G. Evolution of the photoluminescence (PL) as a function of the frequency of radio-frequency field, from 400 kHz to 14.3 MHz. The upper right box show the $I_N=1$ level scheme of the $^{14}$N nuclear spin in the $\ket{0_e}$ state. The $^{13}$C down-arrow shows the expected peak at the $^{13}$C spin Larmor frequency. b),c) Enlarged spectra corresponding to the two dashed boxes in a), showing resonances associated with the $^{14}$N nuclear spins coupled to NV$^-$ centers in the $\ket{\pm 1_e}$ manifolds.
• Figure 4: a) Photo-ionization (P.I.) and radio-frequency excitation of the $^{14}\mathrm{N}$ spin in the NV$^0$ charge state. b) c) Optically Detected Nuclear Magnetic Resonance (ODNMR) spectrum at B= 486.8 G showing resonances associated with $^{14}$N nuclear spins coupled to the NV$^0$ center in the $\ket{\pm/1/2_e}$ manifolds.
• Figure 5: (Left) Energy levels of the $^{13}$C nuclear spins in the $\ket{\pm 1_e}$ states. a),b) and c) are close-up of the ODNMR resonances arising from the coupling between $^{13}$C nuclei and NV electronic spins in the $\ket{\pm 1_e}$ magnetic states. Blue dots correspond to experimental data and red lines to Lorentzian fits. The resonance frequencies are reported on Tab.\ref{['tab:ms_splitting']}. Resonances are labeled by the $^{13}$C family and using the NV electronic spin in index.