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Tuning a circular p–n junction in graphene from quantum confinement to optical guiding

Nature Nanotechnology volume 12, pages 10451049 (2017) | Download Citation

Abstract

The photon-like propagation of the Dirac electrons in graphene, together with its record-high electronic mobility1,2,3, can lead to applications based on ultrafast electronic response and low dissipation4,5,6. However, the chiral nature of the charge carriers that is responsible for the high mobility also makes it difficult to control their motion and prevents electronic switching. Here, we show how to manipulate the charge carriers by using a circular p–n junction whose size can be continuously tuned from the nanometre to the micrometre scale7,8. The junction size is controlled with a dual-gate device consisting of a planar back gate and a point-like top gate made by decorating a scanning tunnelling microscope tip with a gold nanowire. The nanometre-scale junction is defined by a deep potential well created by the tip-induced charge. It traps the Dirac electrons in quantum-confined states, which are the graphene equivalent of the atomic collapse states (ACSs) predicted to occur at supercritically charged nuclei9,10,11,12,13. As the junction size increases, the transition to the optical regime is signalled by the emergence of whispering-gallery modes14,15,16, similar to those observed at the perimeter of acoustic or optical resonators, and by the appearance of a Fabry–Pérot interference pattern17,18,19,20 for junctions close to a boundary.

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References

  1. 1.

    , , , & The electronic properties of graphene. Rev. Mod. Phys. 81, 109–162 (2009).

  2. 2.

    , & The focusing of electron flow and a Veselago lens in graphene p–n junctions. Science 315, 1252–1255 (2007).

  3. 3.

    , & Chiral tunnelling and the Klein paradox in graphene. Nat. Phys. 2, 620–625 (2006).

  4. 4.

    , , & Gate-controlled guiding of electrons in graphene. Nat. Nanotech. 6, 222–225 (2011).

  5. 5.

    , & Observation of negative refraction of Dirac fermions in graphene. Nat. Phys. 11, 925–929 (2015).

  6. 6.

    et al. Electron optics with p–n junctions in ballistic graphene. Science 353, 1522–1525 (2016).

  7. 7.

    & Scattering of two-dimensional massless Dirac electrons by a circular potential barrier. Phys. Rev. B 90, 235402 (2014).

  8. 8.

    , & Mie scattering analog in graphene: lensing, particle confinement, and depletion of Klein tunneling. Phys. Rev. B 87, 155409 (2013).

  9. 9.

    & On the energy levels of systems with Z >1/137. J. Phys. USSR 9, 97–100 (1945).

  10. 10.

    , & Atomic collapse and quasi-Rydberg states in graphene. Phys. Rev. Lett. 99, 246802 (2007).

  11. 11.

    et al. Observing atomic collapse resonances in artificial nuclei on graphene. Science 340, 734–737 (2013).

  12. 12.

    et al. Realization of a tunable artificial atom at a supercritically charged vacancy in graphene. Nat. Phys. 12, 545–549 (2016).

  13. 13.

    et al. Screening charged impurities and lifting the orbital degeneracy in graphene by populating Landau levels. Phys. Rev. Lett. 112, 036804 (2014).

  14. 14.

    CXII. The problem of the whispering gallery. Philos. Mag. Ser. 6 20, 1001–1004 (1910).

  15. 15.

    et al. Creating and probing electron whispering-gallery modes in graphene. Science 348, 672–675 (2015).

  16. 16.

    & Optical resonators with whispering-gallery modes-part I: basics. IEEE J. Sel. Top. Quantum Electron. 12, 3–14 (2006).

  17. 17.

    et al. Ballistic interferences in suspended graphene. Nat. Commun. 4, 2342 (2013).

  18. 18.

    et al. Imaging electrostatically confined Dirac fermions in graphene quantum dots. Nat. Phys. 12, 1032–1036 (2016).

  19. 19.

    , , , & Klein tunnelling and electron trapping in nanometre-scale graphene quantum dots. Nat. Phys. 12, 1069–1075 (2016).

  20. 20.

    et al. An on/off Berry phase switch in circular graphene resonators. Science 356, 845–849 (2017).

  21. 21.

    Scanning tunneling microscopy and spectroscopy of graphene on insulating substrates. Phys. Status Solidi B 248, 2423–2434 (2011).

  22. 22.

    , & Electronic properties of graphene: a perspective from scanning tunneling microscopy and magnetotransport. Rep. Prog. Phys. 75, 056501 (2012).

  23. 23.

    , & Screening of a hypercritical charge in graphene. Phys. Rev. B 76, 233402 (2007).

  24. 24.

    et al. Metallic, magnetic and molecular nanocontacts. Nat. Nanotech. 11, 499–508 (2016).

  25. 25.

    et al. Quantized thermal transport in single-atom junctions. Science 355, 1192–1195 (2017).

  26. 26.

    , , , & Observing a scale anomaly in graphene: a universal quantum phase transition. Nat. Commun. Preprint at (15 January 2017).

  27. 27.

    , & A ballistic pn junction in suspended graphene with split bottom gates. Appl. Phys. Lett. 102, 223102 (2013).

  28. 28.

    et al. Single-mode and multimode Fabry–Pérot interference in suspended graphene. Phys. Rev. B 89, 121414 (2014).

  29. 29.

    , & Scanning tunneling microscopy and spectroscopy of graphene layers on graphite. Solid State Commun. 149, 1151–1156 (2009).

  30. 30.

    et al. Local, global, and nonlinear screening in twisted double-layer graphene. Proc. Natl Acad. Sci. USA 113, 6623–6628 (2016).

  31. 31.

    et al. Visualizing strain-induced pseudomagnetic fields in graphene through an hBN magnifying glass. Nano Lett. 17, 2839–2843 (2017).

  32. 32.

    , & Self-navigation of a scanning tunneling microscope tip toward a micron sized sample. Rev. Sci. Instrum. 82, 073701 (2011).

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Acknowledgements

The authors acknowledge funding provided by DOE-FG02-99ER45742 (STM/STS) and NSF DMR 1708158 (fabrication). Theoretical work was supported by ESF-EUROCORES-EuroGRAPHENE, FWO-VI and the Methusalem program of the Flemish government.

Author information

Author notes

    • Yuhang Jiang
    • , Jinhai Mao
    •  & Dean Moldovan

    These authors contributed equally to this work.

Affiliations

  1. Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08855, USA

    • Yuhang Jiang
    • , Jinhai Mao
    • , Guohong Li
    •  & Eva Y. Andrei
  2. Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium

    • Dean Moldovan
    • , Massoud Ramezani Masir
    •  & Francois M. Peeters
  3. Department of Physics, University of Texas at Austin, Austin, Texas 78712, USA

    • Massoud Ramezani Masir
  4. Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

    • Kenji Watanabe
    •  & Takashi Taniguchi

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Contributions

Y.J., J.M. and E.Y.A. conceived the work and designed the research strategy. Y.J. and J.M. performed the experiments, analysed data and wrote the paper. G.L. built the STM. D.M., M.R.M. and F.M.P. carried out the theoretical work. K.W. and T.T. contributed the boron nitride. E.Y.A. directed the project, analysed the data and wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Eva Y. Andrei.

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https://doi.org/10.1038/nnano.2017.181

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