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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 • 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 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
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 • Wave densities for injected beam polarized along x or z direction • Diffraction patterns (charge lattices)
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
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)
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 Charge lattice (symmetric) Spin lattice(anti-symmetric)
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 Thomas Schulthess Oak Ridge National Laboratory (865) 574-4344 schulthesstc@ornl.gov Gonzalo Alvarez Oak Ridge National Laboratory (865) 241-5498 Alvarezcampg@ornl.gov Jun-Qiang Lu Oak Ridge National Laboratory (865) 574-1956 luj1@ornl.gov Xiaoguang Zhang Oak Ridge National Laboratory (865) 241-0200 zhangx@ornl.gov 11 Schulthess_Dynamics_0611