Local spectroscopy of a gate-tunable energy gap in monolayer 1T’-WTe<sub>2</sub>

ORAL

Abstract

The interplay between strong correlation and topology leads to new quantum phases. In monolayer 1T’-WTe2 non-trivial topology gives rise to a quantum spin Hall insulator (QSHI) phase, characterized by helical 1D edge-states surrounding an insulating 2D bulk. Experimental evidence supports quantized conductance through such edge-states, but the nature of the insulating bulk and whether it is dominated by spin-orbit coupling (SOC) or strong correlation remains under debate. Here we have employed scanning tunneling microscopy and spectroscopy (STM/S) on gate-tunable 1T’-WTe2 devices to explore this issue. Our samples were fabricated using a combination of molecular beam epitaxy (MBE) and van der Waals (vdW) stacking, which allows us to synthesize high-quality monolayer 1T’-WTe2 films on a gate-tunable graphene field-effect transistor supported by hBN. Gate-dependent STS reveals a substantial energy gap in 1T’-WTe2 at charge neutrality, but the gap diminishes when the Fermi level is tuned into either the conduction or valence band. STS across the sample edges shows that edge-states persist at all gate voltages, and Fourier-Transform-STM measurement of the bulk states shows an evolution of the bulk band structure with carrier density. We will discuss the comparison of our data with existing theoretical models such as SOC-induced gapping and a proposed excitonic insulator phase.

–

Presenters

  • Tiancong Zhu

    • University of California, Berkeley

Authors

  • Tiancong Zhu

    • University of California, Berkeley

  • Zehao He

    • University of California, Berkeley

  • Michal Papaj

    • University of California, Berkeley

  • Samuel Stolz

    • University of California, Berkeley

  • Tianye Wang

    • University of California Berkeley

  • Yalong Yuan

    • Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS)

  • Canxun Zhang

    • University of California, Berkeley

  • Yan-Qi Wang

    • University of Maryland, College Park

  • Kenji Watanabe

    • National Institute for Materials Science
    • NIMS
    • Research Center for Electronic and Optical Materials, National Institute for Materials Science
    • Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
    • National Institute for Material Science

  • Takashi Taniguchi

    • Kyoto Univ
    • National Institute for Materials Science
    • Research Center for Materials Nanoarchitectonics
    • Research Center for Materials Nanoarchitectonics, National Institute for Materials Science
    • National Institute for Materials Sciences
    • NIMS
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
    • National Institute for Material Science
    • International Center for Materials Nanoarchitectonics, NIMS, Japan
    • International Center for Materials Nanoarchitectonics, Tsukuba
    • National Institue for Materials Science
    • Kyoto University
    • National Institute of Materials Science
    • International Center for Materials Nanoarchitectonics and National Institute for Materials Science

  • Alex K Zettl

    • University of California, Berkeley

  • Guangyu Zhang

    • Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences (CAS)

  • Joel E Moore

    • University of California, Berkeley

  • Zi Q. Qiu

    • University of California at Berkeley
    • University of California, Berkeley

  • Feng Wang

    • University of California, Berkeley & LBNL
    • University of California, Berkeley

  • Michael F Crommie

    • University of California, Berkeley