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G. S. Diniz and S. E. Ulloa

Spin-orbit coupling and electronic transport in carbon nanotubes in external fields. G. S. Diniz and S. E. Ulloa. Department of Physics and Astronomy , Ohio University , Athens -OH. Supported by. G. S. Diniz and S. E. Ulloa. Boston, APS March Meeting 2012. Motivation & Outline.

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G. S. Diniz and S. E. Ulloa

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  1. Spin-orbit coupling and electronic transport in carbon nanotubes in external fields G. S. Diniz and S. E. Ulloa Departmentof Physics and Astronomy, Ohio University, Athens-OH Supported by G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  2. Motivation & Outline • Spin-orbit effects can play an important effect on electronic structure of CNT, hence its conductance • Fully control of the spin dependent transport • Implementation in spintronic devices In this presentation… • Uniform transverse electric field • Uniform parallel magnetic field • SO interaction (modeled using atomic SOI) • Curvature effects G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  3. Theoretical Model: 4-orbitals tight-binding Hamiltonian Tight-binding Hamiltonian for the whole System Htotal= HL + HLC + HC + HCR + HR Hamiltonian for the Central Conductor B-Field HC = Hhop+HE-field+HB-field+HSOI The local terms: E-field, B-Field and SOI E-Field del Valle et al. PRB (2011); Izumidaet al. JPSJ (2009); Klinovajaet al. PRL (2011);Klinovajaet al. PRB (2011); Jeonget al. PRB (2009), F. Kuemmethet al.Nature (2008). . G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  4. Theoretical Model: 4-orbitals tight-binding Hamiltonian The Hopping term including curvature Z θAB1 θAB2 Izumidaet al. JPSJ 78,074707 (2009). B2 B1 d1 π/6-θ d2 ZAB2 ZAB1 d3 ZAB3 B3 z θAB3 Hopping Integrals r σ-π hybridization due to curvature t G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  5. Theoretical Model:conductance in the central region Green’s Function for the Central Conductor with Self-Energies Green’s function for the left/right leads obtained through an iterative procedure The Spin-Polarized Conductance @ the Central Conductor Using the Landauer’s Formula Where the Couplings are Related to the Self-Energies G. S. Diniz and S. E. Ulloa M. B. NardelliPRB 60, 7828 (1999). Lopez Sanchoet al, J. Phys. F: Met. Phys 14, 1205 (1984). Boston, APS March Meeting 2012

  6. Results:conductance (9,0) 2 Without: External fields, Curvature and SOI G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  7. Results:conductance (6,0) G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  8. Results:conductance (6,0) Transverse E-Field G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  9. Results:conductance (6,0) Parallel B-Field Due to Zeeman Field: G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  10. Results: polarization (6,0) Curvature induced gap G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  11. Results: polarization l = 17.052nm G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  12. Conclusion • ModerateSpin polarization for “low” B-field and dependent on CNT’s radius • Tube length can be quite important! • Manipulation of E-fieldand B-fieldis reflected in the transmission, providing a way to control the current through the CNTs • More interesting features in armchair CNTs, results on the way... • Possible utilization of CNTs in spintronic devices exploring SOI effects Thank you! G. S. Diniz and S. E. Ulloa Boston, APS March Meeting 2012

  13. l = 2.842nm l = 11.368nm l = 5.684nm l = 17.052nm

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