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Petascale on Nanoscale: A Green’s Function Plane Wave Code for Nanomaterials ORNL Electron Transport (OReTran) Code. Thomas C. Schulthess Computer Science and Mathematics Division Center for Nanophase Materials Sciences. Successful predictions of new materials. - PowerPoint PPT Presentation
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Petascale on Nanoscale:A Green’s Function Plane Wave Code for NanomaterialsORNL Electron Transport (OReTran) Code
Thomas C. SchulthessComputer Science and Mathematics Division
Center for Nanophase Materials Sciences
2 Schulthess_Dynamics_0611
Boron nitride nanotubes (predicted 1994,synthesized 1996) Pseudopotential
plane wave code
Successful predictions of new materials
Fe/MgO/Fe magnetic tunnel junction (predicted 2001at ORNL, synthesized 2004)
Layer-KKR and quantumtransport code
3 Schulthess_Dynamics_0611
For each energyFor each K-pointFor each energyFor each K-point
Integration of chargedensities over
K-pointsand energies
Integration of chargedensities over
K-pointsand energies
EndEnd
Conductanceand
nonequilibriumcharge density
Conductanceand
nonequilibriumcharge density
StartStartFlowchart of OReTran
ParametersParameters
InitializationInitialization
Fixed energy plane wave basisFixed energy plane wave basis
Block wave functions in the left and right leadsBlock wave functions in the left and right leads
Plane wave propagation matrix in the middle regionPlane wave propagation matrix in the middle region
Transmission and reflection matricesTransmission and reflection matrices
ConductanceConductance
Keldysh Green function andnonequilibrium charge densityKeldysh Green function and
nonequilibrium charge density
ReturnReturn
StartStart
InitializationInitialization
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x
z 2DES in x-z plane
Shaded (Rashba SO) region: Quantum dot array Patterned electrodes
Spin-polarized injection Different left and right
diffracted flux Transverse charge current
depends on the spin polarization of injection
Non-spin-polarized injection No transverse charge current Transverse spin current
Tunable spin Hall effect
5 Schulthess_Dynamics_0611
Spin-polarized injections
Wave densities for injected beam polarized along x or z direction
Diffraction patterns (charge lattices)
(x,z)(x,z) 2
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Transverse charge current
Period of QD array:b = 20 nm
Width of QD array:0 < a < 20 nm
Asymmetric diffraction transverse charge currents
δj depends on spin polarization of injected beam
0.0015
0.0010
0.0005
0.0000
- 0.0005
jj
0 5 10 15 20a (nm)
X
Z
Y
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Selective polarization flipping
Principal beam j0: Transmission P0: Polarization
Spin flipping for injection polarized along x or y
1.0
0.9
0.8
jj00
0 5 10 15 20a (nm)
X
Z
Y
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Magnetic Random Access Memory
Possible application
Different transverse charge current from differentspin-polarized injection: Spin current detector
Principal beamwith near-perfect transmission andhigh spin polarization
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Non-spin-polarized injection
Charge lattice (symmetric)
Spin lattice(anti-symmetric)
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Transverse spin current
No transverse charge current Transverse spin currents defined outside the SO region Real, dissipative, and detectable
Period of QD array:b = 20 nm
Width of QD array:0 < a < 20 nm
0
0.005
0.000
-0.005
-0.010
-0.015
jj
5 10 15 20a (nm)
xjz
yjz
zjz
11 Schulthess_Dynamics_0611
Contacts
11 Schulthess_Dynamics_0611
Gonzalo AlvarezOak Ridge National Laboratory(865) 241-5498Alvarezcampg@ornl.gov
Jun-Qiang LuOak Ridge National Laboratory(865) 574-1956luj1@ornl.gov
Xiaoguang ZhangOak Ridge National Laboratory(865) 241-0200zhangx@ornl.gov
Thomas SchulthessOak Ridge National Laboratory(865) 574-4344schulthesstc@ornl.gov
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