|Ph.D Student||Fischer Ran|
|Subject||Room Temperature Nuclear Polarization Enhancement in|
|Department||Department of Physics||Supervisors||Professor David Gershoni|
|Professor Emeritus Amiram Ron|
|Full Thesis text|
Nuclear spins are a natural choice for applications requiring long relaxation times due to their immunity to unwanted perturbations from the environment. Among the many applications are magnetic resonance-based bio-sensing and quantum computing. However, thermal polarization of nuclear spins, determined by the Boltzmann factor, is particularly low, especially at room temperature. Incidentally, the low coupling of nuclear spins to the environment, which is responsible for their long coherence and relaxation times, also makes it difficult to directly polarize these spins at room temperature. This limitation results in poor sensitivities, requiring methods that achieve an enhancement over thermal polarization.
In this work we report on significantly enhanced bulk nuclear polarization of 13C in diamond at room temperature facilitated by the negatively charged nitrogen-vacancy (NV) color center. We implement two polarization techniques based on the transfer of polarization from the NV center, whose electron spin can be optically pumped, to the nuclear spins of nearby 13C atoms. The first method relies on anti-crossing between the electronic energy levels of the NV center to facilitate the electron-nucleus spin polarization transfer. The second method employs resonant microwave excitation to directly transfer the spin polarization between the two species. Both methods are characterized experimentally by optical detection of magnetic resonance in the single electron-single spin exchange level as well as by nuclear magnetic resonance (NMR) detection of the entire bulk diamond, reaching polarizations up ∼1%. The latter polarization method showed reduced sensitivity to the external magnetic field (orientation and magnitude), which may enable polarization of nuclear spins within diamond powder. Additionally, we demonstrate experimentally the role of the internuclear interaction, namely spin diffusion, in the bulk polarization process opening up a new route into studying the spin diffusion process by controlling the diamond parameters such as NV concentration, 13C enrichment and other paramagnetic impurities within the diamond.