Direct Observation of Dirac-Electron Wedding Cakes in Graphene Quantum Dots

ORAL

Abstract

The ability to apply local nanometer scale gate potentials in graphene heterostructures has recently enabled the creation of quantum dot (QD) resonators inside circular p-n junction rings, where one has detailed control of electron orbits by means of spatial and magnetic confinement. In this talk, we provide the first spatial visualization of the intricate evolution of the energy spectrum, and corresponding wavefunctions, as we condense the QD atomic-like shell states into quantized Landau levels (LLs) in a circular graphene QD. The resonator states are observed to condense into LLs beginning in the resonator center and then progressing to become edge states at the QD boundaries. The formation of compressible and incompressible rings due to Coulomb interactions inside the resonator are observed in detailed spectroscopic mapping at higher magnetic fields where the screened potential develops a prominent wedding cake-like structure. Surprisingly, the inclusion of electron interactions are found to be necessary to describe even very weak field behavior, demonstrating the importance of electron interactions in confined graphene systems.

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Presenters

  • Christopher Gutierrez

    Quantum Matter Institute, University of British Columbia, Univ British Columbia, Quantum Matter Institute, Center for Nanoscale Science and Technology, National Institute of Standards and Technology

Authors

  • Christopher Gutierrez

    Quantum Matter Institute, University of British Columbia, Univ British Columbia, Quantum Matter Institute, Center for Nanoscale Science and Technology, National Institute of Standards and Technology

  • Daniel Walkup

    NIST, Center for Nanoscale Science and Technology, NIST / Maryland NanoCenter, University of Maryland, Center for Nanoscale Science and Technology, NIST -Natl Inst of Stds & Tech, Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Center for Nanoscale Science and Technology, NIST

  • Fereshte Ghahari

    Center for Nanoscale Science and Technology, NIST / Maryland NanoCenter, University of Maryland, Center for Nanoscale Science and Technology, NIST -Natl Inst of Stds & Tech, NIST/University of Maryland, College Park, Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Center for Nanoscale Science and Technology, NIST

  • Cyprian Lewandowski

    Massachusetts Institute of Technology, Department of Physics, Massachusetts Institute of Technology, Physics Department, Massachusetts Institute of Technology

  • Joaquin Rodriguez Nieva

    Harvard University, Department of Physics, Harvard University, Harvard Univ, Physics Department, Harvard University

  • Takashi Taniguchi

    National Institute for Materials Science, NIMS, National Institute for Material Science, Advanced Materials Laboratory, National Institute for Materials Science, National Institute of Materials Science, Research Center for Functional Materials, National Institute for Materials Science, National Institute for Materials Science (NIMS, Advanced Materials Laboratory, NIMS, National Institute for Materials Science, Advanced Materials Laboratory, National Institue for Materials Science, National Institute of Material Science, National Institute for Matericals Science, Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, NIMS-Japan

  • Kenji Watanabe

    National Institute for Materials Science, NIMS, National Institute for Material Science, Advanced Materials Laboratory, National Institute for Materials Science, National Institute of Materials Science, Research Center for Functional Materials, National Institute for Materials Science, National Institute for Materials Science (NIMS, Advanced Materials Laboratory, NIMS, National Institute for Materials Science, Advanced Materials Laboratory, National Institue for Materials Science, National Institute of Material Science, National Institute for Matericals Science, Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Advanced materials laboratory, National institute for Materials Science, NIMS-Japan

  • Leonid Levitov

    Massachusetts Institute of Technology, Department of Physics, Massachusetts Institute of Technology, Physics, Massachusetts Institute of Technology, Massachusetts Inst of Tech-MIT, MIT, Physics Department, Massachusetts Institute of Technology

  • Nikolai Zhitenev

    Center for Nanoscale Science and Technology, NIST, Center for Nanoscale Science and Technology, NIST -Natl Inst of Stds & Tech, NIST -Natl Inst of Stds & Tech, Center for Nanoscale Science and Technology, National Institute of Standards and Technology

  • Joseph Stroscio

    Center for Nanoscale Science and Technology, NIST, Center for Nanoscale Science and Technology, NIST -Natl Inst of Stds & Tech, NIST -Natl Inst of Stds & Tech, Center for Nanoscale Science and Technology, National Institue of Standards and Technology, Center for Nanoscale Science and Technology, National Institute of Standards and Technology, NIST