1 / 11

Thomas C. Schulthess Computer Science and Mathematics Division

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.

daquan-burch
Download Presentation

Thomas C. Schulthess Computer Science and Mathematics Division

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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

  2. 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

  3. 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

  4. 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

  5. Spin-polarized injections • Wave densities for injected beam polarized along x or z direction • Diffraction patterns (charge lattices)

  6. 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

  7. 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)

  8. 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

  9. Non-spin-polarized injection Charge lattice (symmetric) Spin lattice(anti-symmetric)

  10. 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)

  11. 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

More Related