Observation of even denominator fractional quantum Hall states in monolayer graphene

ORAL

Abstract

We report magneto-capacitance measurements of high quality monolayer graphene encapsulated in boron-nitride (hBN) and few-layer graphite. In addition to the usual odd-denominator hierarchy states at partial fillings ν=p/(2p±1), we observe even-denominator ν=±½ and ±¼ states, which appear only for a narrow range of magnetic fields. Similar behavior is observed in 3 different samples, but at dramatically different B: in two of the samples, the even-denominator states appear at B≈28 T, while in the third sample they appear at B≈5.5 T. We trace the difference to the measured zero-magnetic field sublattice splitting, which arises due to the interaction with the hBN subtrate. The ν=±½,¼ FQH states are accompanied by a series of phase transitions and crossovers in the neighboring odd-denominator states, indicative of an underlying isospin phase transition. Mean field analysis suggests this transition is between a low-field valley ordered Kekule phase and a high field canted antiferromagnetic phase. The observed behavior cannot be explained within the composite fermion picture, suggesting a possible intermediate phase between the Kekule distorted phase and the antiferromagnet.

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Presenters

  • Alexander Zibrov

    University of California - Santa Barbara, Department of Physics, University of California, Santa Barbara, Physics Department, University of California, Univ of California - Santa Barbara

Authors

  • Alexander Zibrov

    University of California - Santa Barbara, Department of Physics, University of California, Santa Barbara, Physics Department, University of California, Univ of California - Santa Barbara

  • Eric Spanton

    University of California - Santa Barbara, Stanford Univ, California Nanosystems Institute, University of California, Santa Barbara, California Nanosystems Institute, University of California, Univ of California - Santa Barbara

  • Haoxin Zhou

    University of California - Santa Barbara, Physics Department, University of California, Univ of California - Santa Barbara

  • Carlos Kometter

    Department of Physics, University of California, Santa Barbara, Physics Department, University of California

  • Takashi Taniguchi

    National Institute for Materials Science, NIMS, National Institute for Material Science, Advanced Materials Laboratory, National Institute for Materials Science, National Institute of Materials Science, Research Center for Functional Materials, National Institute for Materials Science, National Institute for Materials Science (NIMS, Advanced Materials Laboratory, NIMS, National Institute for Materials Science, Advanced Materials Laboratory, National Institue for Materials Science, National Institute of Material Science, National Institute for Matericals Science, Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, NIMS-Japan

  • Kenji Watanabe

    National Institute for Materials Science, NIMS, National Institute for Material Science, Advanced Materials Laboratory, National Institute for Materials Science, National Institute of Materials Science, Research Center for Functional Materials, National Institute for Materials Science, National Institute for Materials Science (NIMS, Advanced Materials Laboratory, NIMS, National Institute for Materials Science, Advanced Materials Laboratory, National Institue for Materials Science, National Institute of Material Science, National Institute for Matericals Science, Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Advanced materials laboratory, National institute for Materials Science, NIMS-Japan

  • Andrea Young

    Physics, University of California Santa Barbara, Physics, Univ of California - Santa Barbara, University of California - Santa Barbara, Univ of California - Santa Barbara, Department of Physics, University of California, Santa Barbara, Physics Department, University of California