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Fast Nuclear Spin Hyperpolarization of Phosphorus in Silicon

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. Silicon doped with Phosphorus. Introduction. Introduction. Energy Splitting in Magnetic Field. H 0. Relaxation Times.

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Fast Nuclear Spin Hyperpolarization of Phosphorus in Silicon

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  1. 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

  2. Silicon doped with Phosphorus

  3. Introduction

  4. Introduction

  5. Energy Splitting in Magnetic Field H0

  6. Relaxation Times n2 n4 X 1 1 n1 n3 but Ee ≈ 240 GHz (electric Zeeman) En ≈ 147 MHz (nuclear Zeeman) A≈ 117 MHz (hyperfine interaction) • Tx returns the spin populations n2and n3 to thermal equilibrium with the phonon reservoir • T1 returns the spin populations n4and n3 / n1and n2 to thermal equilibrium with the lattice 1 D. Pines, J. Bardeen, C. Slichter, Phys. Rev. 106, 489 1957

  7. Temperature Tspin (LH2 bath) Tres phonons conduction band valence band Tres ≠ Tspin In general: Tres > Tspin In fact we want: • 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)

  8. Mechanism B=8.5T

  9. Mechanism B=8.5T X

  10. Mechanism 1 1 X B=8.5T

  11. Mechanism B=8.5T 1 1 X

  12. Mechanism B=8.5T 1 1 X

  13. Mechanism B=8.5T 1 1 X

  14. Mechanism Result = net nuclear antipolarization: B=8.5T 1 1 X

  15. Experimental - EPR

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

  17. Conclusion

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

  19. Experimental - EDMR vs. ESR 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

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