• 文献标题:   Competing ordered states with filling factor two in bilayer graphene
  • 文献类型:   Article
  • 作  者:   VELASCO J, LEE Y, ZHANG F, MYHRO K, TRAN D, DEO M, SMIRNOV D, MACDONALD AH, LAU CN
  • 作者关键词:  
  • 出版物名称:   NATURE COMMUNICATIONS
  • ISSN:   2041-1723
  • 通讯作者地址:   Univ Penn
  • 被引频次:   13
  • DOI:   10.1038/ncomms5550
  • 出版年:   2014

▎ 摘  要

The quantum Hall effect, in which a two-dimensional sample's Hall conductivities become quantized, is a remarkable transport anomaly commonly observed at strong magnetic fields. However, it may also appear at zero magnetic field if time-reversal symmetry is broken. Charge-neutral bilayer graphene is unstable to a variety of competing and closely related broken symmetry states, some of which have non-zero quantized Hall conductivities. Here we explore those states by stabilizing them with external fields. Transport spectroscopy measurements reveal two distinct states that have two quantum units of Hall conductivity, stabilized by large magnetic and electric fields, respectively. The majority spins of both phases form a quantum anomalous Hall state, and the minority spins constitute a Kekulestate with spontaneous valley coherence for phase I and a quantum valley Hall state for phase II. Our results shed light on the rich set of competing ordered states in bilayer graphene.