gate control of spin transport in multilayer graphene
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Gate Control of Spin Transport in Multilayer Graphene. By H . Goto et al. Kun Xu. Advantages. Advantages of spin over charge: Easily manipulatable with externally applied magnetic fields Long coherence/relaxation time. GMR. Giant magnetoresistance Sandwich structure FNF

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Presentation Transcript
advantages
Advantages
  • Advantages of spin over charge:
    • Easily manipulatable with externally applied magnetic fields
    • Long coherence/relaxation time
slide3
GMR
  • Giant magnetoresistance
    • Sandwich structure
      • FNF
    • Spin valve (HDD read/write heads)
    • The 2007 Nobel Prize in physics was awarded to Albert Fert and Peter Grünberg for the discovery of GMR
disadvantages
Disadvantages
  • Existing spin devices do not amplify signals
datta das device
Datta-Das Device
  • Current modulated by the degrees of precession in electron spin introduced by the gate field
spin based quantum computer
Spin-based quantum Computer
  • Qubit – intrinsic binary units
  • Quantum entanglement
  • Single electron trapped in a quantum dot
spin transport in graphite based devices
Spin transport in graphite based devices
  • Carbon nanotubes
  • Graphene
  • Multilayer graphene (MLG)
  • Weak spin-orbit and hyperfine interaction
  • Gate control of spin conduction
device structure
Device Structure
  • MLG Exfoliated from kish graphite
  • 2.5nm thick, about 7 layers (by SEM/AFM)
  • Doped Si/SiO2 substrate
device structure1
Device Structure
  • 50nm Co electrodes 200nm/330nm
  • Separated by L=290nm
device structure2
Device Structure
  • Cr/Au nonmagnetic electrodes
  • 5nm/100nm thick
measurement
Measurement
  • Four terminal lock-in technique
  • 4.2K
  • Excitation current of 1.0 uA, 119Hz
  • Back gate bias
spin signal r s
Spin Signal: Rs
  • Rs=Rp-Rap
  • Proportional to R

when FN interfaces are opaque

  • Proportional to 1/R

when FN interfaces are transparent

spin relaxation length1
Spin relaxation length
  • MLG
  • Graphene: 1.5-2 um at room temperaure, may stay the same at low temperature
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