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Fast Nuclear Spin Hyperpolarization of Phosphorus in Silicon E. Sorte, W. Baker, D.R. McCamey, G. Laicher, C. Boehme, B. Saam Department of Physics, University of Utah

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Silicon doped with Phosphorus

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Introduction

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H0H0 Energy Splitting in Magnetic Field

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T x returns the spin populations n 2 and n 3 to thermal equilibrium with the phonon reservoir 1 D. Pines, J. Bardeen, C. Slichter, Phys. Rev. 106, 489 1957 Relaxation Times n4n4 n3n3 n2n2 n1n1 11 11 XX but T 1 returns the spin populations n 4 and n 3 / n 1 and n 2 to thermal equilibrium with the lattice E e ≈ 240 GHz (electric Zeeman) E n ≈ 147 MHz (nuclear Zeeman) A ≈ 117 MHz (hyperfine interaction)

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conduction band valence band phonons T spin (LH 2 bath) T res In general: T res ≠ T spin T res > T spin In fact we want: Temperature Constant illumination generates new charge carriers, leading to steady state with constant density of “hot” electrons As hot electrons cascade toward the lattice temperature, they emit phonons at constant rate. G.Feher, Phys. Rev Lett 3, 135 (1959)

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B=8.5T Mechanism

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B=8.5T XX Mechanism

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B=8.5T XX 11 11 Mechanism

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XX B=8.5T 11 11 Mechanism

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XX B=8.5T 11 11 Mechanism

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XX B=8.5T 11 11 Mechanism

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XX B=8.5T 11 11 Result = net nuclear antipolarization: Mechanism

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Experimental - EPR

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EDMR at T = 1.37 K Xe discharge lamp EDMR at different temperatures Experimental - EDMR D. R. McCamey, J. van Tol, G. W. Morley, C. Boehme, eprint arXiv:0806.3429v1 (2008)

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Conclusion

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NMR on 31 P nucleus to actually “see” the nuclear polarization. Future Experiments

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Comparison of polarization measured using EDMR vs EPR at different intensities of light (Hg discharge) at T = 3 K. Hg discharge has higher spectral temperature, yielding higher polarizations (P=-24% at 3K vs -6% at 3K for Xe lamp) independent of intensity for most part. Polarization with ESR 45% that measured with EDMR Experimental - EDMR vs. ESR

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