Observation of topological bulk-boundary correspondence in a strong-coupling charge density wave state

ORAL

Abstract

The interplay between topology and charge order is at the frontier of condensed matter research. However, there is no direct experimental evidence for a topological bulk-boundary correspondence within a fully gapped charge-ordered state yet. Here, using scanning tunneling microscopy, we directly visualize the topological bulk-boundary correspondence in a topological charge density wave (CDW) material. Below the CDW transition temperature, tunneling spectra on an atomically resolved lattice reveals a large insulating gap (over 500 meV) whose △/kBTc≈20, suggesting a strong coupling nature of the CDW. Remarkably, in an atomically sharp monolayer step edge, we find an in-gap gapless helical state. Both the insulating gap and the gapless edge state disappear above the CDW transition temperature. The presence of the edge state within the insulating CDW gap indicates the topological bulk-boundary correspondence, pointing to the realization of a topological CDW state.

*Funding: Experimental and theoretical work at Princeton University: Gordon and Betty Moore Foundation (GBMF4547 and GBMF9461). Crystal growth: European Research Council (ERC) Advanced Grant No. 742068 (“TOPMAT”), Deutsche Forschungsgemeinschaft (DFG) under SFB 1143 (Project No. 247310070), and Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter—ct.qmat (EXC 2147, Project No. 39085490) and National Science Foundation of China (NSFC) (11734003), the National Key Research and Development Program of China (2016YFA0300600). Y.G.Y. is supported by NSFC (11574029) and the Strategic Priority Research Program of Chinese Academy of Sciences (XDB30000000).

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Presenters

  • Maksim Litskevich

    • Princeton University

Authors

  • Maksim Litskevich

    • Princeton University

  • Md. Shafayat Hossain

    • Princeton University

  • Qi Zhang

    • Princeton University

  • Zijia Cheng

    • Princeton University
    • Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey, USA.

  • Zhiwei Wang

    • Beijing Institute of Technology

  • Satya N Guin

    • Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
    • Max Planck Institute for Chemical Physics of Solids

  • Nitesh Kumar

    • Max Planck Institute for Chemical Physics of Solids

  • Chandra Shekhar

    • Max Planck Institute for Chemical Physics of Solids

  • Yongkai Li

    • Beijing Institute of Technology

  • Ying Yang

    • Beijing Institute of Technology

  • Guoqing Chang

    • Nanyang Technological University
    • Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University

  • Jia-Xin Yin

    • Princeton University
    • Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey, USA.

  • Nana Shumiya

    • Princeton University

  • Yuxiao Jiang

    • Princeton University

  • Guangming Cheng

    • Princeton University

  • Tyler A Cochran

    • Princeton University

  • Daniel Multer

    • Princeton University

  • Xian Yang

    • Princeton University

  • Nan Yao

    • Princeton Institute for Science and Technology of Materials, Princeton University
    • Princeton University

  • Yugui Yao

    • Beijing Institute of Technology

  • Claudia Felser

    • Max Planck Institute for Chemical Physic
    • Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
    • Max Planck Institute for Chemical Physics of Solids

  • Zahid M Hasan

    • Princeton University
    • Laboratory for Topological Quantum Matter and Advanced Spectroscopy (B7), Department of Physics, Princeton University, Princeton, New Jersey, USA.