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Controlling ac transport in carbon-based Fabry -Perot devices

Controlling ac transport in carbon-based Fabry -Perot devices . Claudia Gomes da Rocha University of Jyvaskyla, Finland Dresden University of Technology, Germany. Jyvaskyla, 28 August 2012. 1. Outline. System: graphene nanoribbon devices AC driven devices Theoretical model

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Controlling ac transport in carbon-based Fabry -Perot devices

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  1. Controlling ac transport in carbon-based Fabry-Perot devices Claudia Gomes da Rocha University of Jyvaskyla, Finland Dresden University of Technology, Germany Jyvaskyla, 28 August 2012

  2. 1 Outline System: graphenenanoribbondevices AC drivendevices Theoreticalmodel Results: probingthe control Conclusions / Perspectives Controlling ac transport in carbon-based ... 28 August 2012

  3. 2 Graphene nanodevices DC source X. Wang et. al., PRL 100 (2008) Understand the transport properties of nanodevices composed of graphene nanoribbons Gate voltage nano Controlling ac transport in carbon-based ... 28 August 2012

  4. 3 Carbon-basedinterferometers • Good quality contacts, ballistic transport (no scattering)! Light interferometer Fabry-Perot oscillations W. Lianget al.,Nature411, 665 (2001) Vbias (mV) ”electron cavity” Vgate (V) Controlling ac transport in carbon-based ... 28 August 2012

  5. 4 Controlling Fabry-Perot patterns Armchair-edge L  E5 E4 E3 Energy spectrum E2 Adding a time-dependent term to the gate ∆ E1 Controlling ac transport in carbon-based ... 28 August 2012

  6. 5 Theoretical Model Tien-Gordon approach for AC transport Solving time dependent Schrödinger equation AVERAGE CURRENT Jm– mth order Bessel function of the first kind Vac Vg Monitoring the transmission changes as a function of the AC and DC parameters in AGNRs and ZGNRs X X Vbias Controlling ac transport in carbon-based ... 28 August 2012

  7. 6 AC gate in graphene armchair nanoribbon Vac = 0 ac frequency Quantum Wagon-Wheel effect C.G. Rocha et. al., Phys. Rev. B 81, 115435 (2010) Controlling ac transport in carbon-based ... 28 August 2012

  8. 7 AC gate in graphene armchair nanoribbon MAX MIN 1. DC regime 2. Supression 4. Wagon-Wheel effect 3. Revival and inversion Controlling ac transport in carbon-based ... 28 August 2012

  9. 8 AC gate in graphene armchair nanoribbon Noise power Oscillation amplitude of the Noise is two times bigger than for transmission Controlling ac transport in carbon-based ... 28 August 2012

  10. 9 Magnetic fields can enrich the conductance diagrams Peierls Phase Approximation N S Magnetic flux drain source CHANNEL Quantum flux Gate Magnetic field can promote metal-semiconductor transition in ribbons N S Controlling ac transport in carbon-based ... 28 August 2012

  11. 10 Fabry-Perot of graphene armchair nanoribbon Magnetic fields can enrich the conductance diagrams System is at dc condition Combination of Fabry-Perot and insulator behaviours C.G. Rocha et. al., EPL 94, 47002 (2011) Controlling ac transport in carbon-based ... 28 August 2012

  12. 11 Fabry-Perot of graphene armchair nanoribbon Magnetic fields can enrich the conductance diagrams System is at supression state System is at Wagon-Wheel state C.G. Rocha et. al., EPL 94, 47002 (2011) Controlling ac transport in carbon-based ... 28 August 2012

  13. 12 Lessons taken from graphene armchair nanoribbon under ac/dc conditions Regular energy spectrum  regular Fabry-Perot patterns.ac fields can guide the systems to three different transport states: (i) suppression, (ii) inversion and (iii) Stroboscopic condition.Noise is sensitive to the phase of the transmission amplitude.Magnetic fields enrich the FB diagrams by opening an energy gap (resonator and semiconductor behaviours coexist). Controlling ac transport in carbon-based ... 28 August 2012

  14. 13 Controlling Fabry-Perot patterns Zigzag-edge E5 E4 Energy spectrum E3 E2 E1 Adding a time-dependent term to the gate Controlling ac transport in carbon-based ... 28 August 2012

  15. 14 AC gate in graphene zigzag nanoribbon Vac = 0 ac frequency Regular energy level spacing only at high energy ranges NO Quantum Wagon-Wheel effect in zigzag-edge Controlling ac transport in carbon-based ... 28 August 2012

  16. 15 AC gate in graphene zigzag nanoribbon (c) Partial recovery of DC state (a) DC regime (b) ”Supression” Controlling ac transport in carbon-based ... 28 August 2012

  17. 16 Lessons taken so far from graphene ribbons under ac/dc conditions Zigzag and armchair-edge ribbons: atomic details on the edges are important. F. Miao et al. Science 317, 1530 (2007) Controlling ac transport in carbon-based ... 28 August 2012

  18. 17 Applications: quantum pumping devices (Possibility of generating DC current at zero bias) Altshuler et al. Science 283, 1864 (1999) + f() Dissipated power ~ I x V AC Controlling ac transport in carbon-based ... 28 August 2012

  19. 18 Applications: quantum pumping devices Controlling ac transport in carbon-based ... 28 August 2012

  20. 19 Controlling ac transport in carbon-based ... 28 August 2012

  21. 20 Controlling ac transport in carbon-based ... 28 August 2012

  22. 21 Controlling ac transport in carbon-based ... 28 August 2012

  23. 22 Controlling ac transport in carbon-based ... 28 August 2012

  24. 23 Applications: quantum pumping devices Current is amplified when the pumping is tuned nearby van Hove singularity. Charge neutrality point: I  2 van Hove singularity: I   L.E.F. Foa Torres, C.G. Rocha, et. al., APL 99, 092102 (2011) Controlling ac transport in carbon-based ... 28 August 2012

  25. 24 Lessons taken from graphene-based quantum pumping Graphene nanoribbons are promising transmission channels for quantum pumping; When pumped nearby a van Hove singularity, its current is amplified; The current scales linearily with the frequency. Controlling ac transport in carbon-based ... 28 August 2012

  26. 25 Acknowledges Dr. L. E. Foa Torres (UNC, Argentina) Prof. Dr. G. Cuniberti (TUD, Germany) Prof. Dr. A. Latge (UFF, Brazil) THANK YOU FOR THE ATTENTION Controlling ac transport in carbon-based ... 28 August 2012

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