Band conductivity oscillations in a gate-tunable graphene superlattice

Electrons exposed to a two-dimensional (2D) periodic potential and a uniform, perpendicular magnetic field exhibit a fractal, self-similar energy spectrum known as the Hofstadter butterfly. Recently, related high-temperature quantum oscillations (Brown-Zak oscillations) were discovered in graphene m...

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Bibliographic Details
Published in:Nature communications 2022-05, Vol.13 (1), p.2856-2856, Article 2856
Main Authors: Huber, Robin, Steffen, Max-Niklas, Drienovsky, Martin, Sandner, Andreas, Watanabe, Kenji, Taniguchi, Takashi, Pfannkuche, Daniela, Weiss, Dieter, Eroms, Jonathan
Format: Article
Language:English
Subjects:
639/766/119/544
639/766/119/995
639/925/918/1052
Conductivity
Cyclotrons
Electrons
Energy spectra
Graphene
Heat resistance
High temperature
Humanities and Social Sciences
Magnetic fields
Magnetic flux
multidisciplinary
Oscillations
Science
Science (multidisciplinary)
Self-similarity
Superlattices
Unit cell
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Summary:Electrons exposed to a two-dimensional (2D) periodic potential and a uniform, perpendicular magnetic field exhibit a fractal, self-similar energy spectrum known as the Hofstadter butterfly. Recently, related high-temperature quantum oscillations (Brown-Zak oscillations) were discovered in graphene moiré systems, whose origin lies in the repetitive occurrence of extended minibands/magnetic Bloch states at rational fractions of magnetic flux per unit cell giving rise to an increase in band conductivity. In this work, we report on the experimental observation of band conductivity oscillations in an electrostatically defined and gate-tunable graphene superlattice, which are governed both by the internal structure of the Hofstadter butterfly (Brown-Zak oscillations) and by a commensurability relation between the cyclotron radius of electrons and the superlattice period (Weiss oscillations). We obtain a complete, unified description of band conductivity oscillations in two-dimensional superlattices, yielding a detailed match between theory and experiment. Experiments in a tunable graphene superlattice show that the unusual 1/B periodic resistance oscillations at high temperatures in the energy spectrum of electrons in a 2D periodic potential, known as the Hofstadter butterfly, coexist with oscillations due to commensurability between the electron cyclotron radius and the superlattice’s period.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-022-30334-3