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Electrically tunable transverse magnetic focusing in graphene

Nature Physics volume 9, pages 225229 (2013) | Download Citation

Abstract

Electrons in a periodic lattice can propagate without scattering for macroscopic distances despite the presence of the non-uniform Coulomb potential due to the nuclei1. Such ballistic motion of electrons allows the use of a transverse magnetic field to focus electrons2. This phenomenon, known as transverse magnetic focusing (TMF), has been used to study the Fermi surface of metals3 and semiconductor heterostructures4, as well as to investigate Andreev reflection3 and spin–orbit interaction5, and to detect composite fermions6,7. Here we report on the experimental observation of TMF in high-mobility mono-, bi- and tri-layer graphene devices. The ability to tune the graphene carrier density enables us to investigate TMF continuously from the hole to the electron regime and analyse the resulting focusing fan. Moreover, by applying a transverse electric field to tri-layer graphene, we use TMF as a ballistic electron spectroscopy method to investigate controlled changes in the electronic structure of a material. Finally, we demonstrate that TMF survives in graphene up to 300 K, by far the highest temperature reported for any system, opening the door to new room-temperature applications based on electron-optics.

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Acknowledgements

We thank L. Levitov and A. Yacoby for discussions. We acknowledge financial support from National Science Foundation Career Award No. DMR-0845287 and the Office of Naval Research GATE MURI. This work made use of the MRSEC Shared Experimental Facilities supported by the National Science Foundation under award No. DMR-0819762 and of Harvard’s Center for Nanoscale Systems (CNS), supported by the National Science Foundation under grant No. ECS-0335765.

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Affiliations

  1. Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA

    • Thiti Taychatanapat
  2. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

    • Thiti Taychatanapat
    •  & Pablo Jarillo-Herrero
  3. National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan

    • Kenji Watanabe
    •  & Takashi Taniguchi

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Contributions

T. Taychatanapat fabricated the samples and performed the experiments. K.W. and T. Taniguchi synthesized the hBN samples. T. Taychatanapat and P.J-H. carried out the data analysis and co-wrote the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Pablo Jarillo-Herrero.

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DOI

https://doi.org/10.1038/nphys2549

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