Imaging Topologically Emergent Dirac States of a Kondo Insulator

Invited

Abstract

Correlated topological matter is a frontier in the search for exotic quantum phases. Theory now predicts that heavy fermion systems, fertile grounds for discovery in strongly interacting electronic materials, may host such novel phases in the form of topological Kondo insulators. Within these systems, a correlation-driven gap protected by a bulk topological invariant is predicted to harbor emergent surface modes that are entangled with f-electrons, spawning heavy Dirac fermions. In stark contrast to conventional surface states of the non-interacting topological insulators, heavy Dirac fermions are expected to give rise to exotic Dirac liquid states, non-Abelian quantum statistics and topological order. In search of these strongly interacting topological states SmB6 has recently emerged as the most promising candidate. However, no experiments have directly observed the correlated ground state and its emergent heavy Dirac fermions. Here we report the use of heavy fermion quasiparticle interference imaging and co-tunneling spectroscopy to resolve the topological nature of SmB6. On cooling through TΔ* ≈ 35 K we observe the opening of a Kondo insulator gap that expands to Δ* ≈ 10 meV at 2 K, in agreement with transport studies. Within the gap, momentum space imaging reveals flatly dispersing Dirac surface states with effective masses reaching m* = (330 ±20)me. Collectively, our observations demonstrate existence of a strongly correlated topological phase hosting the heaviest known Dirac fermions. The prodigious density of the Dirac states observed near zero energy magnifies their susceptibility to novel orders anticipated for interacting topological matter. Further, direct access at the material surface lifts prospects for manipulation and interface engineering necessary for next-generation quantum devices and universal topological quantum computation.

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Presenters

  • Mohammad Hamidian

    Harvard University, University of California at Davis, Physics, Harvard University

Authors

  • Mohammad Hamidian

    Harvard University, University of California at Davis, Physics, Harvard University

  • Harris Pirie

    Physics, Harvard University

  • Yang He

    Department of Physics, Harvard University, Physics, Harvard University

  • Anjan Soumyanarayanan

    Physics, Harvard University

  • Michael Yee

    Physics, Harvard University

  • Dae-Jeong Kim

    Physics, University of California, Irvine

  • Priscila Rosa

    Los Alamos National Laboratory, Condensed Matter and Magnetic Science Group, Los Alamos National Laboratory, Condensed Matter and Magnet Science Group, Los Alamos National Laboratory

  • Joe Thompson

    MPA-CMMS, Los Alamos National Laboratory, Los Alamos National Laboratory, Condensed Matter and Magnetic Science Group, Los Alamos National Laboratory, Los Alamos Natl Lab, Condensed Matter and Magnet Science Group, Los Alamos National Laboratory

  • Zachary Fisk

    Physics and Astronomy, University of California, Department of Physics and Astronomy, Univ of California - Irvine, Department of Physics and Astronomy, University of California - Irvine, University of California Irvine, University of California, Irvine, Physics, University of California, Los Alamos National Laboratory, Department of Physics, University of California, Physics, University of California, Irvine, Department of Physics and Astronomy, University of California, Irvine

  • Dirk Morr

    Physics, Univ of Illinois - Chicago, Physics, University of Illinois at Chicago

  • Jennifer Hoffman

    Physics, Harvard University, Department of Physics, Harvard University