• 文献标题:   High-order fractal states in graphene superlattices
  • 文献类型:   Article
  • 作  者:   KUMAR RK, MISHCHENKO A, CHEN X, PEZZINI S, AUTON GH, PONOMARENKO LA, ZEITLER U, EAVES L, FAL KO VI, GEIM AK
  • 作者关键词:   graphene, superlattice, hofstadter butterfly
  • 出版物名称:   PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
  • ISSN:   0027-8424
  • 通讯作者地址:   Univ Manchester
  • 被引频次:   5
  • DOI:   10.1073/pnas.1804572115
  • 出版年:   2018

▎ 摘  要

Graphene superlattices were shown to exhibit high-temperature quantum oscillations due to periodic emergence of delocalized Bloch states in high magnetic fields such that unit fractions of the flux quantum pierce a superlattice unit cell. Under these conditions, semiclassical electron trajectories become straight again, similar to the case of zero magnetic field. Here, we report magnetotransport measurements that reveal second-, third-, and fourth-order magnetic Bloch states at high electron densities and temperatures above 100 K. The recurrence of these states creates a fractal pattern intimately related to the origin of Hofstadter butterflies. The hierarchy of the fractal states is determined by the width of magnetic minibands, in qualitative agreement with our band-structure calculations.