Jonathan P. King

Optical polarization of 13 C nuclei in diamond through nitrogen vacancy centers

Zeeman state with a bulk-average polarization up to 5.2%, although local polarization may be higher. The kinetics of polarization are temperature independent and occur within 5 min. Fluctuations in the dipolar field of the NV-center spin bath are identified as the mechanism by which nuclear-spin transitions are induced near defect centers. Polarization is then transported to the bulk material via spin diffusion, which accounts for the observed kinetics of polarization. These results indicate control over the nuclear-spin bath, a methodology to study dynamics of an NV-center ensemble, and application to sensitivity-enhanced NMR.

Room-temperature in situ nuclear spin hyperpolarization from optically pumped nitrogen vacancy centres in diamond

Low detection sensitivity stemming from the weak polarization of nuclear spins is a primary limitation of magnetic resonance spectroscopy and imaging. Methods have been developed to enhance nuclear spin polarization but they typically require high magnetic fields, cryogenic temperatures or sample transfer between magnets. Here we report bulk, room-temperature hyperpolarization of 13C nuclear spins observed via high-field magnetic resonance. The technique harnesses the high optically induced spin polarization of diamond nitrogen vacancy centres at room temperature in combination with dynamic nuclear polarization. We observe bulk nuclear spin polarization of 6%, an enhancement of ∼170,000 over thermal equilibrium. The signal of the hyperpolarized spins was detected in situ with a standard nuclear magnetic resonance probe without the need for sample shuttling or precise crystal orientation. Hyperpolarization via optical pumping/dynamic nuclear polarization should function at arbitrary magnetic fields enabling orders of magnitude sensitivity enhancement for nuclear magnetic resonance of solids and liquids under ambient conditions.

Measurement of untruncated nuclear spin interactions via zero- to ultralow-field nuclear magnetic resonance

Author(s): Blanchard, JW; Sjolander, TF; King, JP; Ledbetter, MP; Levine, EH; Bajaj, VS; Budker, D; Pines, A | Abstract:

Optically rewritable patterns of nuclear magnetization in gallium arsenide

The control of nuclear spin polarization is important to the design of materials and algorithms for spin-based quantum computing and spintronics. Towards that end, it would be convenient to control the sign and magnitude of nuclear polarization as a function of position within the host lattice. Here we show that, by exploiting different mechanisms for electron-nuclear interaction in the optical pumping process, we are able to control and image the sign of the nuclear polarization as a function of distance from an irradiated GaAs surface. This control is achieved using a crafted combination of light helicity, intensity and wavelength, and is further tuned via use of NMR pulse sequences. These results demonstrate all-optical creation of micron scale, rewritable patterns of positive and negative nuclear polarization in a bulk semiconductor without the need for ferromagnets, lithographic patterning techniques, or quantum-confined structures.

Transition-Selective Pulses in Zero-Field Nuclear Magnetic Resonance

We use low-amplitude, ultralow frequency pulses to drive nuclear spin transitions in zero and ultralow magnetic fields. In analogy to high-field NMR, a range of sophisticated experiments becomes available as these allow narrow-band excitation. As a first demonstration, pulses with excitation bandwidths 0.5-5 Hz are used for population redistribution, selective excitation, and coherence filtration. These methods are helpful when interpreting zero- and ultralow-field NMR spectra that contain a large number of transitions.

Antisymmetric Couplings Enable Direct Observation of Chirality in Nuclear Magnetic Resonance Spectroscopy

Here we demonstrate that a term in the nuclear spin Hamiltonian, the antisymmetric J-coupling, is fundamentally connected to molecular chirality. We propose and simulate a nuclear magnetic resonance (NMR) experiment to observe this interaction and differentiate between enantiomers without adding any additional chiral agent to the sample. The antisymmetric J-coupling may be observed in the presence of molecular orientation by an external electric field. The opposite parity of the antisymmetric coupling tensor and the molecular electric dipole moment yields a sign change of the observed coupling between enantiomers. We show how this sign change influences the phase of the NMR spectrum and may be used to discriminate between enantiomers.

Helicity independent optically-pumped nuclear magnetic resonance in gallium arsenide

We present new phenomenology for optically-pumped nuclear magnetic resonance (OPNMR) of gallium arsenide. When pumping at low irradiation intensity, the OPNMR signal becomes independent of light helicity. The results are consistent with a mechanism in which the bulk signal represents competition between nuclear quadrupolar and electron-nuclear hyperfine relaxation. This mechanism is further supported by the scaling behavior of OPNMR for isotopes with varying hyperfine and quadrupolar interactions. These results indicate the magnitude and sign of nuclear polarization in the sample may be controlled as a function of depth by tuning photon energy and laser intensity, portending submicron scale patterning of nuclear magnetization.