Electric Field Tuned Quantum Phase Transition from Topological to Conventional Insulator in Few-Layer Na3Bi

ORAL

Abstract

Na3Bi in bulk is a zero-bandgap topological Dirac semimetal (TDS), but when confined to a few layers it is predicted to be a large-gap (~300 meV) topological insulator. Application of an electric field to few-layer Na3Bi has been predicted to drive a band inversion due to Stark effect and induce a topological phase transition, which could be the basis of a topological transistor. Here we demonstrate the growth of epitaxial few-layer Na3Bi via MBE, and probe its electronic structure and response to an electric field using scanning probe microscopy/spectroscopy (STM/STS) and angle-resolved photoelectron spectroscopy, and compare with results from DFT.1 Both monolayer and bilayer Na3Bi show bandgaps >300 meV in STS, and the observation of an edge state with exponential decay into the bulk confirms their topological nature, consistent with DFT. With application of an electric field via potassium doping or approach of the STM tip the bandgap can be tuned to semi-metallic and then re-opened to greater than 100 meV. The electric fields required to induce this transition are below the breakdown field of many conventional dielectrics, making the creation of a topological transistor based on a few-layer TDS within reach.


1 J.L. Collins et al., arXiv:1805.08378 (to appear in Nature)

–

Presenters

  • James Collins

    Department of Physics and Astronomy and Centre for Future Low Energy Electronics Technologies, Monash University, ARC Centre of Excellence in Future Low-Energy Electronics Technologies

Authors

  • James Collins

    Department of Physics and Astronomy and Centre for Future Low Energy Electronics Technologies, Monash University, ARC Centre of Excellence in Future Low-Energy Electronics Technologies

  • Anton Tadich

    Australian Synchrotron

  • Lidia Gomes

    Department of Physics and Centre for Advanced 2D Materials, National University of Singapore, University of Illinois at Urbana-Champaign

  • João Rodrigues

    Department of Physics and Centre for Advanced 2D Materials, National University of Singapore, Department of Physics, University of Illinois at Urbana Champaign

  • John Hellerstedt

    School of Physics and Astronomy, Monash University, Institute of Physics, ASCR, v.v.i., Department of Physics and Astronomy and Centre for Future Low Energy Electronics Technologies, Monash University

  • Chang Liu

    Department of Physics and Astronomy and Centre for Future Low Energy Electronics Technologies, Monash University, ARC Centre of Excellence in Future Low-Energy Electronics Technologies

  • Hyejin Ryu

    Lawrence Berkeley National Laboratory, Lawrance Berkeley National Laboratory, Lawrence Berkeley Nat. Lab

  • Shujie Tang

    ALS, Lawrence Berkeley National Laboratory, Lawrance Berkeley National Laboratory, Stanford University, SIMES, Stanford University, Advanced Light Source, Lawrence Berkeley National Laboratory

  • Weikang Wu

    Singapore University of Technology and Design

  • Shengyuan Yang

    Singapore University of Technology and Design, Engineering Product Development, Singapore University of Technology and Design, Science and Math, Singapore University of Technology and Design, Research Laboratory for Quantum Materials, Singapore University of Technology and Design

  • Shaffique Adam

    Department of Physics and Centre for Advanced 2D Materials, National University of Singapore, Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Department of Physics, National University of Singapore, Yale-NUS College, National University of Singapore

  • Sung-Kwan Mo

    ALS, Lawrence Berkeley National Laboratory, Lawrance Berkeley National Laboratory, Lawrence Berkeley Nat. Lab, Advanced Light Source, Lawrence Berkeley National Laboratory

  • Michael Fuhrer

    Department of Physics and Astronomy and Centre for Future Low Energy Electronics Technologies, Monash University, Physics and Astronomy, Monash Univ, School of Physics & Astronomy, Monash University, ARC Centre of Excellence in Future Low-Energy Electronics Technologies

  • Mark T Edmonds

    School of Physics and Astronomy, Monash University, Department of Physics and Astronomy and Centre for Future Low Energy Electronics Technologies, Monash University, ARC Centre of Excellence in Future Low-Energy Electronics Technologies