Tunable moiré bands and strong correlations in small-twist-angle bilayer graphene

Kyounghwan Kim, Ashley DaSilva, Shengqiang Huang, Babak Fallahazad, Stefano Larentis, Takashi Taniguchi, Kenji Watanabe, Brian J. LeRoy, Allan H. MacDonald, Emanuel Tutuc

Research output: Contribution to journalArticlepeer-review

212 Scopus citations

Abstract

According to electronic structure theory, bilayer graphene is expected to have anomalous electronic properties when it has long-period moiré patterns produced by small misalignments between its individual layer honeycomb lattices. We have realized bilayer graphene moiré crystals with accurately controlled twist angles smaller than 1° and studied their properties using scanning probe microscopy and electron transport. We observe conductivity minima at charge neutrality, satellite gaps that appear at anomalous carrier densities for twist angles smaller than 1°, and tunneling densities-of-states that are strongly dependent on carrier density. These features are robust up to large transverse electric fields. In perpendicular magnetic fields, we observe the emergence of a Hofstadter butterfly in the energy spectrum, with fourfold degenerate Landau levels, and broken symmetry quantum Hall states at filling factors ±1, 2, 3. These observations demonstrate that at small twist angles, the electronic properties of bilayer graphene moiré crystals are strongly altered by electron-electron interactions.

Original languageEnglish (US)
Pages (from-to)3364-3369
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number13
DOIs
StatePublished - Mar 28 2017

Keywords

  • Graphene
  • Hofstadter butterfly
  • Moiré band
  • Moiré crystal
  • Twisted bilayer

ASJC Scopus subject areas

  • General

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