Visualizing the Coulomb blockade in graphene quantum dots; Part II

ORAL

Abstract

The Coulomb blockade (CB) is one of the most characteristic phenomena of nanoscale artificial atoms. Here, we created circular quantum dots (QD) in exfoliated graphene on hexagonal boron nitride (hBN), by locally ionizing defects in the hBN using the tip of a scanning tunneling microscope (STM). At high magnetic fields, the gaps between Landau levels (LLs) create insulating barriers inside and around the QDs, enabling a capacitive interaction with the STM tip, sample, and back gate electrodes. Inside the QDs, dI/dV spectra reveal a series of CB peaks, alongside local density of states peaks due to LLs. By sweeping the gate voltage, we construct spectroscopic gate maps in which the Coulomb peaks appear as lines, whose slope is governed by the capacitances between dot, tip, and sample electrodes, and whose offsets reveal the addition spectrum of the QDs. Each LL has its own series of charging lines, creating anticrossings whose characteristics reflect the interactions between electrons in different LLs, and depend strongly on both the magnetic field and the gate voltage, especially at weaker fields. By moving the STM tip, we can tune the tip-dot capacitance, and tunnel into different parts of the dot, enabling a full characterization of the anticrossings of these coulomb peaks.

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Presenters

  • 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

Authors

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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