Odd Integer Quantum Hall States with Interlayer Coherence in Twisted Bilayer Graphene

Youngwook Kim, Pilkyung Moon, Kenji Watanabe, Takashi Taniguchi, Jurgen H. Smet

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14 Scopus citations

Abstract

We report on the quantum Hall effect in two stacked graphene layers rotated by 2°. The tunneling strength among the layers can be varied from very weak to strong via the mechanism of magnetic breakdown when tuning the density. Odd-integer quantum Hall physics is not anticipated in the regime of suppressed tunneling for balanced layer densities, yet it is observed. We interpret this as a signature of Coulomb interaction induced interlayer coherence and Bose-Einstein condensation of excitons that form at half filling of each layer. A density imbalance gives rise to reentrant behavior due to a phase transition from the interlayer coherent state to incompressible behavior caused by simultaneous condensation of both layers in different quantum Hall states. With increasing overall density, magnetic breakdown gains the upper hand. As a consequence of the enhanced interlayer tunneling, the interlayer coherent state and the phase transition vanish.

Original languageEnglish
Pages (from-to)4249-4254
Number of pages6
JournalNano Letters
Volume21
Issue number10
DOIs
StatePublished - 26 May 2021

Bibliographical note

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Keywords

  • Bose-Einstein condensation
  • interlayer coherence
  • quantum Hall effect
  • twisted bilayer graphene

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