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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.

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Petascale on Nanoscale:A Green’s Function Plane Wave Code for NanomaterialsORNL Electron Transport (OReTran) Code

Thomas C. Schulthess

Computer Science and Mathematics Division

Center for Nanophase Materials Sciences


Successful predictions of new materials
Successful predictions of new materials

  • Fe/MgO/Fe magnetic tunnel junction (predicted 2001at ORNL, synthesized 2004)

    • Layer-KKR and quantumtransport code

  • Boron nitride nanotubes (predicted 1994,synthesized 1996)

    • Pseudopotentialplane wave code


Flowchart of oretran
Flowchart of OReTran

Start

Start

Initialization

Initialization

Fixed energy plane wave basis

Parameters

Block wave functions in the left and right leads

For each energy

For each K-point

Conductanceand nonequilibriumcharge density

Plane wave propagation matrix in the middle region

Transmission and reflection matrices

Integration of chargedensities overK-pointsand energies

Conductance

Keldysh Green function andnonequilibrium charge density

End

Return


Tunable spin hall effect

z

x

Tunable spin Hall effect

  • 2DES in x-z plane

  • Shaded (Rashba SO) region:

    • Quantum dot array

    • Patterned electrodes

  • Spin-polarized injection

    • Different left and rightdiffracted flux

    • Transverse charge currentdepends on the spin polarization of injection

  • Non-spin-polarized injection

    • No transverse charge current

    • Transverse spin current


Spin polarized injections
Spin-polarized injections

  • Wave densities for injected beam polarized along x or z direction

  • Diffraction patterns (charge lattices)


Transverse charge current

X

Y

Z

Transverse charge current

0.0015

  • Period of QD array:b = 20 nm

  • Width of QD array:0 < a < 20 nm

0.0010

0.0005

j

0.0000

- 0.0005

0

5

10

15

20

a (nm)

  • Asymmetric diffraction  transverse charge currents

  • δj depends on spin polarization of injected beam


Selective polarization flipping

X

Y

Z

Selective polarization flipping

1.0

  • Principal beam

    • j0: Transmission

    • P0: Polarization

  • Spin flipping for injection polarized along x or y

0.9

j0

0.8

0

5

10

15

20

a (nm)


Possible application

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


Non spin polarized injection
Non-spin-polarized injection

Charge lattice (symmetric)

Spin lattice(anti-symmetric)


Transverse spin current
Transverse spin current

0.005

  • No transverse charge current

  • Transverse spin currents defined outside the SO region

  • Real, dissipative, and detectable

0.000

  • Period of QD array:b = 20 nm

  • Width of QD array:0 < a < 20 nm

-0.005

xjz

j

yjz

-0.010

zjz

-0.015

5

10

15

20

0

a (nm)


Contacts
Contacts

Thomas Schulthess

Oak Ridge National Laboratory

(865) 574-4344

[email protected]

Gonzalo Alvarez

Oak Ridge National Laboratory

(865) 241-5498

[email protected]

Jun-Qiang Lu

Oak Ridge National Laboratory

(865) 574-1956

[email protected]

Xiaoguang Zhang

Oak Ridge National Laboratory

(865) 241-0200

[email protected]

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