Brown-Zak oscillations and second-order magnetic Bloch states in graphene/hBN superlattices

ORAL

Abstract

We report on a novel type of magneto-quantum oscillation which was recently observed and studied in graphene/hexagonal-boron nitride superlattices [1]. Surprisingly, the oscillations only become clearly noticeable above liquid helium temperatures (100 K), after Shubnikov-de Haas oscillations and the associated spectral gaps become smeared. These so-called BZ oscillations are extremely robust with respect to temperature and were found to exist even at 373 K (100oC) in a relatively weak magnetic field (B = 4 T). In addition, the oscillations are periodic in 1/B with a fundamental frequency which is independent on carrier density, and that is governed only by the magnetic field value (B0) when one flux quantum pierces the superlattice unit cell. The effect originates from the magnetic translation group, first proposed by Brown and Zak in the 60’s, which states that translational symmetry is restored in the electron wave function for particular values of B, when the quantum magnetic length is commensurable with the lattice periodicity. The BZ oscillations are also used as a probe to study self-similarity and the zero-effective magnetic field associated with different fractals of the corresponding magnetic Bloch states.
[1] R. Krishna Kumar et al, Science 357, 181-184 (2017)

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Presenters

  • Roshan Krishna Kumar

    School of Physics & Astronomy, University of Manchester

Authors

  • Roshan Krishna Kumar

    School of Physics & Astronomy, University of Manchester

  • Xi Chen

    National Graphene Institute, University of Manchester

  • Gregory Auton

    National Graphene Institute, University of Manchester

  • Artem Mishchenko

    School of Physics & Astronomy, University of Manchester, School of Physics and Astronomy, University of Manchester

  • Denis Bandurin

    School of Physics & Astronomy, University of Manchester, University of Manchester

  • Serge Morozov

    Institute of Microelectronics Technology and High Purity Materials, RAS

  • Yang Cao

    National Graphene Institute, University of Manchester, School of Physics and Astronomy, University of Manchester, University of Manchester

  • Ekaterina Khestanova

    School of Physics & Astronomy, University of Manchester

  • Moshe Ben Shalom

    School of Physics & Astronomy, University of Manchester

  • Andre Kretinin

    National Graphene Institute, University of Manchester

  • Laurence Eaves

    School of Physics & Astronomy, University of Nottingham

  • Konstantin Novoselov

    School of Physics & Astronomy, University of Manchester

  • Irina Grigorieva

    School of Physics & Astronomy, University of Manchester, School of Physics and Astronomy, University of Manchester

  • Leonid Ponomarenko

    Department of Physics, University of Lancaster

  • Vladimir Falko

    National Graphene Institute, University of Manchester, Physics, University of Manchester

  • Andre Geim

    School of Physics & Astronomy, University of Manchester, School of Physics and Astronomy, University of Manchester, University of Manchester