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Gate Control of Spin Transport in Multilayer Graphene By H. Goto et al. Kun Xu.

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Presentation on theme: "Gate Control of Spin Transport in Multilayer Graphene By H. Goto et al. Kun Xu."— Presentation transcript:

1 Gate Control of Spin Transport in Multilayer Graphene By H. Goto et al. Kun Xu

2 Advantages Advantages of spin over charge: Easily manipulatable with externally applied magnetic fields Long coherence/relaxation time

3 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

4 Disadvantages Existing spin devices do not amplify signals

5 Datta-Das Device Current modulated by the degrees of precession in electron spin introduced by the gate field

6 Spin-based quantum Computer Qubit – intrinsic binary units Quantum entanglement Single electron trapped in a quantum dot

7 Spin transport in graphite based devices Carbon nanotubes Graphene Multilayer graphene (MLG) Weak spin-orbit and hyperfine interaction Gate control of spin conduction

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9 Device Structure MLG Exfoliated from kish graphite 2.5nm thick, about 7 layers (by SEM/AFM) Doped Si/SiO2 substrate

10 Device Structure 50nm Co electrodes 200nm/330nm Separated by L=290nm

11 Device Structure Cr/Au nonmagnetic electrodes 5nm/100nm thick

12 Measurement Four terminal lock-in technique 4.2K Excitation current of 1.0 uA, 119Hz Back gate bias

13 Spin Signal: R s Rs=Rp-Rap Proportional to R when FN interfaces are opaque Proportional to 1/R when FN interfaces are transparent

14 Spin Signal: R s

15 Vn=1.5V

16 Spin relaxation length

17 MLG Graphene: um at room temperaure, may stay the same at low temperature

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