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 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
Datta & Das, APL 56, 665 (1990)

4. Electrical spin injection
Schmidt et al., PRL 92, (2004)
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 ϕσ=ϕAB+σϕSO 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