Ferroelectric quantum Hall phase revealed by visualizing interference of Landau level wavefunctions

ORAL

Abstract

Novel broken symmetry states can spontaneously form due to Coulomb interactions in electronic systems with multiple internal degrees of freedom. A powerful approach to distinguish among such states in two-dimensional systems is to visualize their wavefunctions with a scanning tunneling microscope (STM)1. Here we investigate bismuth surface states, where strong spin-orbit coupling leads to six degenerate teardrop-shaped hole pockets. Our spectroscopic measurements reveal that this valley degeneracy is fully lifted at high magnetic field as a result of exchange interactions. We image the corresponding Landau level (LL) wavefunctions with a STM to address the nature of valley ordering for the case of a singly degenerate LL. The spatial patterns we observe around isolated defects contain unique signatures of interference between spin-textured valleys, which identifies the electronic ground state as a quantum Hall ferroelectric. Our observations confirm the recent prediction2 that interactions in strongly anisotropic valley systems favor the occupation of a single valley, which gives rise to ferroelectricity in bismuth.
1B. E. Feldman*, M. T. Randeria* et al., Science 354, 316 (2016)
2I. Sodemann et al., arxiv:1701.07836

*We acknowledge the Moore Foundation, DOE, NSF-DMR and NSF-MRSEC

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Presenters

  • Mallika Randeria

    • Joseph Henry Laboratories & Department of Physics, Princeton University
    • Princeton University

Authors

  • Mallika Randeria

    • Joseph Henry Laboratories & Department of Physics, Princeton University
    • Princeton University

  • Benjamin Feldman

    • Joseph Henry Laboratories & Department of Physics, Princeton University
    • Princeton University

  • Fengcheng Wu

    • Argonne National Laboratory
    • Department of Physics, Univerisity of Texas at Austin
    • Argonne National Lab

  • Hao Ding

    • Joseph Henry Laboratories & Department of Physics, Princeton University
    • Princeton University

  • Andras Gyenis

    • Department of Electrical Engineering, Princeton University
    • Princeton University, Department of Electrical Engineering
    • Princeton University
    • Electrical Engineering, Princeton University

  • Huiwen Ji

    • Department of Chemistry, Princeton University
    • Princeton University

  • Robert Cava

    • Department of Chemistry, Princeton University
    • Princeton
    • Princeton University
    • Chemistry, Princeton Univ
    • Princeton Univ

  • Allan MacDonald

    • Physics department, University of Texas at Austin
    • Physics, University of Texas, Austin
    • Department of Physics, The University of Texas at Austin
    • Physics , Univ of Texas, Austin
    • Univ of Texas at Austin
    • Physics, The University of Texas at Austin
    • Department of Physics, Univerisity of Texas at Austin
    • The University of Texas at Austin
    • University of Texas

  • Ali Yazdani

    • Physics department, Princeton Univ
    • Joseph Henry Laboratories & Department of Physics, Princeton University
    • Physics Department, Princeton University
    • Physics, Princeton University
    • Princeton University