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Magneto-optical reflectance studies of a quasi-one-dimensional topological insulator $\alpha-Bi_4I_4$

POSTER

Abstract

$\alpha-Bi_4I_4$, a small-bandgap, quasi-one-dimensional topological insulator, was predicted to host a rare high-order-topological order and helical hinge states. Recent high-resolution ARPES measurements found that the quasi-1D Dirac-like surface state on the (100) surface opens a gap of $\approx$ 35 meV within the bulk bandgap, consistent with the theoretic predictions. Here we report high-magnetic-field optical reflectance measurements of the (100) surfaces in the Voigt geometry ($B//E//(100)$) at liquid helium temperatures. The reflectance referenced to the zero-field data exhibits multiple prominent inter-band transitions both in the far-infrared and mid-infrared range, with constant, linear, quadratic, or non-monotonic dependences on the magnetic field. This allows the identification of Landau level dispersions and inverted band gaps. The observation of the two lowest energy band transitions at 14.2 meV and 16.4 meV may be related to the topological surface states.

Authors

  • Youcheng Wang

    National High Magnetic Field Laboratory

  • Robert Grzywacz

    Moscow Institute of Physics and Technology, University of Virginia, California Institute of Technology, National High Magnetic Field Laboratory, University and Student Affairs; Oak Ridge Laboratory, Brookhaven National Laboratory, Physicist, Brookhaven National Laboratory, Oak Ridge National Laboratory, USA, Center for Nuclear Study, University of Tokyo, Advanced Science Research Center, Japan Atomic Energy Agency, Florida State University, Presidency University, Kolkata, INDIA, VECC,Kolkata, INDIA, SINP,Kolkata, INDIA, UGC-DAE CSR (Kolkata), INDIA, IFIN-HH, ELI-NP, Romania, Variable Energy Cyclotron Centre,Kolkata, INDIA, IEM, Kolkata, India, Victoria Institution (College), Kolkata, INDIA, Variable Energy Cyclotron Centre, Kolkata, INDIA, NHMFL; Florida State University, FAMU-FSU College of Engineering, Florida State University, Physics Department, Florida State University, Mississippi State University, NHMFL-FSU, U. Colorado at Boulder, NHMFL, University of Alabama at Birmingham, Oak Ridge National Laboratory, Argonne National Laboratory, Alabama School of Math and Science, University of South Alabama, University of Florida, University of Notre Dame, University of Texas at Dallas, Bob Jones University, University of Tennessee at Chattanooga, The Autonomous University of San Luis Potosí, Northern Arizona University, Flagstaff, AZ, Harvard-Smithsonian Center for Astrophysics, Cambridge, National Institute of Standards and Technology, Clemson University, University of South Florida, Phenikaa University, University of Ulsan, Ohio University, University of Hawaii, University of California, Davis, University of California, Davis., Saleh Research Centre, Department of Physics, Florida State university, Tallahassee, FL32306, USA, WestCHEM, School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK, Professor, facility manager, Student, Florida State University(Former), Hebrew University, Israel \& Ioffe Institute, St.\ Petersburg, Russia, University of Tennessee, Knoxville

  • Robert Grzywacz

    Moscow Institute of Physics and Technology, University of Virginia, California Institute of Technology, National High Magnetic Field Laboratory, University and Student Affairs; Oak Ridge Laboratory, Brookhaven National Laboratory, Physicist, Brookhaven National Laboratory, Oak Ridge National Laboratory, USA, Center for Nuclear Study, University of Tokyo, Advanced Science Research Center, Japan Atomic Energy Agency, Florida State University, Presidency University, Kolkata, INDIA, VECC,Kolkata, INDIA, SINP,Kolkata, INDIA, UGC-DAE CSR (Kolkata), INDIA, IFIN-HH, ELI-NP, Romania, Variable Energy Cyclotron Centre,Kolkata, INDIA, IEM, Kolkata, India, Victoria Institution (College), Kolkata, INDIA, Variable Energy Cyclotron Centre, Kolkata, INDIA, NHMFL; Florida State University, FAMU-FSU College of Engineering, Florida State University, Physics Department, Florida State University, Mississippi State University, NHMFL-FSU, U. Colorado at Boulder, NHMFL, University of Alabama at Birmingham, Oak Ridge National Laboratory, Argonne National Laboratory, Alabama School of Math and Science, University of South Alabama, University of Florida, University of Notre Dame, University of Texas at Dallas, Bob Jones University, University of Tennessee at Chattanooga, The Autonomous University of San Luis Potosí, Northern Arizona University, Flagstaff, AZ, Harvard-Smithsonian Center for Astrophysics, Cambridge, National Institute of Standards and Technology, Clemson University, University of South Florida, Phenikaa University, University of Ulsan, Ohio University, University of Hawaii, University of California, Davis, University of California, Davis., Saleh Research Centre, Department of Physics, Florida State university, Tallahassee, FL32306, USA, WestCHEM, School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK, Professor, facility manager, Student, Florida State University(Former), Hebrew University, Israel \& Ioffe Institute, St.\ Petersburg, Russia, University of Tennessee, Knoxville

  • Bing Lv

    University of Texas at Dallas

  • Fan Zhang

    University of Texas at Dallas

  • Guangxin Ni

    National High Magnetic Field Laboratory, Florida State University