{
  "id": "1402.4288",
  "version": "v4",
  "published": "2014-02-18T10:57:12.000Z",
  "updated": "2014-05-05T08:57:42.000Z",
  "title": "Efficient Dynamic Polarization of Phosphorus Nuclei in Silicon in Strong Magnetic Fields and Low Temperatures",
  "authors": [
    "J. Järvinen",
    "D. Zvezdov",
    "J. Ahokas",
    "S. Sheludyakov",
    "O. Vainio",
    "L. Lehtonen",
    "S. Vasiliev",
    "Y. Fujii",
    "S. Mitsudo",
    "T. Mizusaki",
    "M. Gwak",
    "SangGap Lee",
    "Soonchil Lee",
    "L. Vlasenko"
  ],
  "categories": [
    "cond-mat.mes-hall"
  ],
  "abstract": "We demonstrate that the dynamic nuclear polarization (DNP) of phosphorus donors in silicon can be very effective in a magnetic field of 4.6 T and at temperatures below 1 K. The DNP occurs due to the Overhauser effect following a cross relaxation via the forbidden flip-flop or flip-flip transitions. Nuclear polarization values $P>0.98$ were reached after 20 min of pumping with 0.4 $\\mu$W of microwave power. We evaluated that the ratio of hyperfine state populations increased by three orders of magnitude after 2 hours of pumping, and an extremely pure nuclear spin system containing $<10^{-11}$ of the other spin state can be created. An inverted DNP has been obtained by pumping the low field ESR line of P followed by the flip-flip cross relaxation. This transition has much smaller relaxation rate and required substantially longer pumping times. We found that the nuclear polarization dynamics deviates substantially from a simple exponential function. The evolution of the polarization is characterized by two time constants $T^{'}_{ac}\\approx$15 s in the beginning, and $T^{\"}_{ac}\\approx$1100 s for long pumping time. Temperature dependence of the nuclear relaxation rate of $^{31}$P was studied down to 0.75 K, below which the relaxation time became too long to be measured. The nuclear polarization followed a bi-exponential time dependence during relaxation. We suggest that the non-exponential behavior of DNP dynamics and the subsequent relaxation is mediated by the nuclei of $^{29}$Si surrounding $^{31}$P donors, which affect the transition probabilities of the forbidden cross-relaxation processes.",
  "revisions": [
    {
      "version": "v4",
      "updated": "2014-05-05T08:57:42.000Z"
    }
  ],
  "analyses": {
    "subjects": [
      "76.70.-r",
      "71.55.Cn",
      "76.30.-v",
      "76.60.Es"
    ],
    "keywords": [
      "strong magnetic fields",
      "efficient dynamic polarization",
      "pure nuclear spin system",
      "phosphorus nuclei",
      "nuclear polarization"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1103/PhysRevB.90.214401",
      "journal": "Physical Review B",
      "year": 2014,
      "month": "Dec",
      "volume": 90,
      "number": 21,
      "pages": 214401
    },
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2014PhRvB..90u4401J"
    }
  }
}