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Spin-orbit interaction in semiconductor quantum dots systems

Spin-orbit interaction in semiconductor quantum dots systems. Sergio Ulloa et al. Department of Physics and Astronomy and Nanoscale and Quantum Phenomena Institute Ohio University Athens, OH. Spin-orbit interaction in semiconductors. Effective magnetic field perp. to P:

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Spin-orbit interaction in semiconductor quantum dots systems

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  1. Spin-orbit interaction in semiconductor quantum dots systems Sergio Ulloa et al. Department of Physics and Astronomy and Nanoscale and Quantum Phenomena Institute Ohio University Athens, OH

  2. Spin-orbit interaction in semiconductors • Effective magnetic field perp. to P: • Spin precession along its path • Strong and tunable electric fields on the electronic system • Rashba field appearing from a top gate • Side gates can generate lateral fields  quantum point contacts

  3. Datta & Das, APL 56, 665 (1990) Datta-Das spin transistor 1. Spin-polarized electron injection from a ferromagnetic (FM) source 2. Manipulation of spin via top-gate-controlled spin-orbit coupling 3. Detection of spin-polarized electrons via FM drain

  4. Schmidt et al., PRL 92, 226601 (2004) Electrical spin injection • Suppression of electron spin polarization at finite voltage • Large variation of experimental results • Controlled, high spin injection so far elusive

  5. Spin-orbit effects in … quantum dots rings  Aharonov-Casher and Aharonov-Bohm effects quantum point contacts  lateral spin-orbit fields

  6. Lateral SO in QPCs – P. Debray half-plateau only for VERY asymmetric QPC potentials InAs GaAs QPC field dependence InAs B in plane B perpendicular

  7. QPC + SO  Full polarization?Anh Ngo + SEU strongly asymmetric potential in QPC polarization? yes, but weak … half-plateau only if strong Zeeman field larger polarization possible but no half plateau

  8. Interactions needed: NEGF calculation J. Wan + M. Cahay – U Cinci

  9. Dots-in-ring M. Heiblum • Aharonov-Bohm flux allow measurement of relative phases • SO spin-dependent phases become relevant even if leads are unpolarized • how is the Kondo effect in such a dot affected by SO and AB phases? ϕσ=ϕAB+σϕSO recent expts in AB+SO (p-type GaAs) Grbc et al PRL 2007 theory ……..

  10. Dot-in-ring once around: the importance of symmetry Edson Vernek + Nancy Sandler + SEU single-particle self-energy for QD orbital depends on AB and SO phases only through ϕσ … but relative amplitude of the effect depends on V2 strong particle-hole asymmetry

  11. Dot-in-ring – turn on interactions in the dot: U=0.5, εd=-U/2 NRG calculations increasing ϕSO quickly destroys Kondo screening Kondo peak decreases for both spin species local moment increases reducing V2 reduces the effect akin to local Zeeman field?

  12. Including a local Zeeman field restores Kondo screening

  13. Spin filtering in the Kondo regime

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