Visualization and Manipulation of Bilayer Graphene Quantum Dots with Broken Rotational Symmetry and Nontrivial Topology

Zhehao Ge, Frederic Joucken, Eberth Quezada, Diego R. Da Costa, John Davenport, Brian Giraldo, Takashi Taniguchi, Kenji Watanabe, Nobuhiko P. Kobayashi, Tony Low, Jairo Velasco

Research output: Contribution to journalArticlepeer-review

Abstract

Electrostatically defined quantum dots (QDs) in Bernal stacked bilayer graphene (BLG) are a promising quantum information platform because of their long spin decoherence times, high sample quality, and tunability. Importantly, the shape of QD states determines the electron energy spectrum, the interactions between electrons, and the coupling of electrons to their environment, all of which are relevant for quantum information processing. Despite its importance, the shape of BLG QD states remains experimentally unexamined. Here we report direct visualization of BLG QD states by using a scanning tunneling microscope. Strikingly, we find these states exhibit a robust broken rotational symmetry. By using a numerical tight-binding model, we determine that the observed broken rotational symmetry can be attributed to low energy anisotropic bands. We then compare confined holes and electrons and demonstrate the influence of BLG's nontrivial band topology. Our study distinguishes BLG QDs from prior QD platforms with trivial band topology.

Original languageEnglish (US)
Pages (from-to)8682-8688
Number of pages7
JournalNano letters
Volume20
Issue number12
DOIs
StatePublished - Dec 9 2020

Bibliographical note

Funding Information:
J.V.J. acknowledges support from the National Science Foundation under award DMR-1753367 and the Army Research Office under contract W911NF-17-1-0473. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, Grant Number JPMXP0112101001, JSPS KAKENHI Grant Numbers JP20H00354 and the CREST(JPMJCR15F3), JST.

Keywords

  • Berry curvature
  • bilayer graphene
  • quantum dots
  • quantum information
  • scanning tunneling microscopy

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