title: Submillisecond hyperpolarization of nuclear spins in silicon.
abstract: In this Letter, we devise a fast and effective nuclear spin hyperpolarization scheme, which is, in principle, magnetic field independent. We use this scheme to experimentally demonstrate polarizations of up to 66% for phosphorus donor nuclear spins in bulk silicon, which are created within less than 100  μs in a magnetic field of 0.35 T at a temperature of 5 K. The polarization scheme is based on a spin-dependent recombination process via weakly coupled spin pairs, for which the recombination time constant strongly depends on the relative orientation of the two spins. We further use this scheme to measure the nuclear spin relaxation time and find a value of ∼100  ms under illumination, in good agreement with the value calculated for nuclear spin flips induced by repeated ionization and deionization processes.
authors.affiliation: Walter Schottky Institut, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Hoehne
authors.affiliation: Walter Schottky Institut, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Lukas
authors.initials: L
authors.lastname: Dreher
authors.affiliation: Walter Schottky Institut, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: David P
authors.initials: DP
authors.lastname: Franke
authors.affiliation: Walter Schottky Institut, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Stutzmann
authors.affiliation: A. F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia.
authors.forename: Leonid S
authors.initials: LS
authors.lastname: Vlasenko
authors.affiliation: School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohuku-ku, Yokohama 223-8522, Japan.
authors.forename: Kohei M
authors.initials: KM
authors.lastname: Itoh
authors.affiliation: Walter Schottky Institut, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Martin S
authors.initials: MS
authors.lastname: Brandt