Electrostatically Confined Monolayer Graphene Quantum Dots with Orbital and Valley Splittings

Nils M. Freitag, Larisa A. Chizhova, P. Nemes-Incze, Colin R. Woods, Roman V. Gorbachev, Yang Cao, Andre K. Geim, Kostya S. Novoselov, Joachim Burgdörfer, Florian Libisch, Markus Morgenstern

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

The electrostatic confinement of massless charge carriers is hampered by Klein tunneling. Circumventing this problem in graphene mainly relies on carving out nanostructures or applying electric displacement fields to open a band gap in bilayer graphene. So far, these approaches suffer from edge disorder or insufficiently controlled localization of electrons. Here we realize an alternative strategy in monolayer graphene, by combining a homogeneous magnetic field and electrostatic confinement. Using the tip of a scanning tunneling microscope, we induce a confining potential in the Landau gaps of bulk graphene without the need for physical edges. Gating the localized states toward the Fermi energy leads to regular charging sequences with more than 40 Coulomb peaks exhibiting typical addition energies of 7-20 meV. Orbital splittings of 4-10 meV and a valley splitting of about 3 meV for the first orbital state can be deduced. These experimental observations are quantitatively reproduced by tight binding calculations, which include the interactions of the graphene with the aligned hexagonal boron nitride substrate. The demonstrated confinement approach appears suitable to create quantum dots with well-defined wave function properties beyond the reach of traditional techniques.

Original languageEnglish
Pages (from-to)5798-5805
Number of pages8
JournalNano Letters
Volume16
Issue number9
DOIs
Publication statusPublished - Sep 14 2016

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Graphene
Semiconductor quantum dots
valleys
Monolayers
graphene
quantum dots
orbitals
Plasma confinement
Electrostatics
electrostatics
Boron nitride
boron nitrides
Wave functions
Fermi level
Charge carriers
confining
charging
charge carriers
Nanostructures

Keywords

  • Graphene
  • Landau quantization
  • orbital splitting
  • quantum dot
  • STM
  • valley splitting

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

Cite this

Freitag, N. M., Chizhova, L. A., Nemes-Incze, P., Woods, C. R., Gorbachev, R. V., Cao, Y., ... Morgenstern, M. (2016). Electrostatically Confined Monolayer Graphene Quantum Dots with Orbital and Valley Splittings. Nano Letters, 16(9), 5798-5805. https://doi.org/10.1021/acs.nanolett.6b02548

Electrostatically Confined Monolayer Graphene Quantum Dots with Orbital and Valley Splittings. / Freitag, Nils M.; Chizhova, Larisa A.; Nemes-Incze, P.; Woods, Colin R.; Gorbachev, Roman V.; Cao, Yang; Geim, Andre K.; Novoselov, Kostya S.; Burgdörfer, Joachim; Libisch, Florian; Morgenstern, Markus.

In: Nano Letters, Vol. 16, No. 9, 14.09.2016, p. 5798-5805.

Research output: Contribution to journalArticle

Freitag, NM, Chizhova, LA, Nemes-Incze, P, Woods, CR, Gorbachev, RV, Cao, Y, Geim, AK, Novoselov, KS, Burgdörfer, J, Libisch, F & Morgenstern, M 2016, 'Electrostatically Confined Monolayer Graphene Quantum Dots with Orbital and Valley Splittings', Nano Letters, vol. 16, no. 9, pp. 5798-5805. https://doi.org/10.1021/acs.nanolett.6b02548
Freitag, Nils M. ; Chizhova, Larisa A. ; Nemes-Incze, P. ; Woods, Colin R. ; Gorbachev, Roman V. ; Cao, Yang ; Geim, Andre K. ; Novoselov, Kostya S. ; Burgdörfer, Joachim ; Libisch, Florian ; Morgenstern, Markus. / Electrostatically Confined Monolayer Graphene Quantum Dots with Orbital and Valley Splittings. In: Nano Letters. 2016 ; Vol. 16, No. 9. pp. 5798-5805.
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