Multispin-assisted optical pumping of bulk C13 nuclear spin polarization in diamond

Abstract

One of the most remarkable properties of the nitrogen-vacancy (NV) center in diamond is that optical illumination initializes its electronic spin almost completely, a feature that can be exploited to polarize other spin species in their proximity. Here we use field-cycled nuclear magnetic resonance (NMR) to investigate the mechanisms of spin polarization transfer from NVs to 13 C spins in diamond at room temperature. We focus on the dynamics near 51 mT, where a fortuitous combination of energy matching conditions between electron and nuclear spin levels gives rise to alternative polarization transfer channels. By monitoring the 13 C spin polarization as a function of the applied magnetic field, we show 13 C spin pumping takes place via a multi-spin cross relaxation process involving the NVspin and the electronic and nuclear spins of neighboring P1 centers. Further, we find that this mechanism is insensitive to the crystal orientation relative to the magnetic field, although the absolute level of 13 C polarization ⎯ reaching up to ~3% under optimal conditions ⎯ can vary substantially depending on the interplay between optical pumping efficiency, photo-generated carriers, and laser-induced heating.

Two-Electron-Spin Ratchets as a Platform for Microwave-Free Dynamic Nuclear Polarization of Arbitrary Material Targets

“…Recent experimental observations demonstrating efficient P1-mediated carbon polarization in diamond for θ approaching ~20 deg. are consistent with this notion 17 . Fig.…”

How to detect qubit-environment entanglement generated during qubit dephasing

“…The justification is twofold: (1) without dynamic nuclear polarization (DNP), the density operator of the environment at low fields isR(0) ∝ 1, and according to Eq. (4) there is no QEE for such initial states; (2) DNP of the environment of an NV center has been recently mastered [61][62][63][64][65][66][67][68][69] and its presence is expected to enhance the signal that the qubit experiences. We assume that R(0) does not contain any correlations between the nuclei, i.e.R(0) = kρ k , whereρ k is the density matrix of k-th nucleus, given in the case of spin-1/2 nuclei bŷ ρ k = 01 (τ, t) coherence signals (normalized by the maximum qubit coherence) of an NV center qubit interacting with partially polarized nuclear environment for a single randomly generated spatial arrangement of environmental spins, plotted for t = τ at magnetic field Bz = 200 G. Dashed, dot-dashed and solid lines correspond to polarization radius rp = 0.6 (one spin polarized), 0.7 (five spins polarized) and 0.9 nm (nineteen spins polarized), respectively.…”

Carbon-13 dynamic nuclear polarization in diamond via a microwave-free integrated cross effect

“…To test our DNP model, we implement the protocol sketched in Fig. 2A comprising low-field optical DNP followed by detection via 13 C NMR at 9 T. A full description of our experimental setup has been presented in prior work (21). Briefly, we use a homemade shuttling mechanism to physically move the sample (a 3×3×0.3-mm 3 diamond crystal with natural 13 C abundance, and NV and P1 concentrations of ∼10 and ∼50 ppm, respectively) in and out of the sweet spot of the NMR magnet.…”

“…Assuming the presence of a magnetic field B, we focus on the system dynamics near the "energymatching" condition, where the Zeeman splitting between the P1's jm ' S = +1=2i and jm ' S = −1=2i states nearly coincides with the NV jm s = 0i ↔ jm s = −1i energy difference. Central to this regime is the emergence of hyperfine-shifted "avoided energy crossings" at select magnetic fields, whose exact values depend on the NV axis orientation relative to B. NVs and P1s can "cross-relax" near these fields, typically with the assistance of coupled nuclear spins, which, therefore, dynamically polarize (21,22). Rather than operating at a constant B, however, the present DNP protocol uses a magnetic field of variable magnitude to sweep across the full set of avoided crossings in the presence of continuous optical excitation.…”