Observation of Chiral Surface Excitons in a Topological Insulator Bi<sub>2</sub>Se<sub>3 </sub>

ORAL

Abstract

Photoluminescence (PL) emission arising due to recombination of excitons in conventional semiconductors is usually unpolarized because of scattering by collective modes during exciton thermalization. Here on the contrary, we observe almost perfectly polarization-preserving PL peak centered at 2.3 eV from the surface of an archetypical three-dimensional topological insulator (TI), Bi2Se3. Based on the dependences of the PL spectra on the energy and polarization of incident photons, we propose that the observed PL can be semi-quantitatively explained by composite particles – chiral excitons – formed by the Coulomb attraction between massless (Dirac) electrons and massive holes, both subject to strong spin-orbit coupling which locks their spins and momenta into chiral textures. We experimentally demonstrate that the chiral excitons can be optically oriented with circularly polarized light in a broad range of excitation energies between 2.5 to 2.8 eV, and that the orientation remains preserved even at room temperature.

*HHK, AL and GB acknowledge support from NSF DMR-1104884. DLM acknowledges support from NSF DMR-1720816. XW and SWC acknowledge support from NSF DMREF-DMR-1629059.

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Presenters

  • Hsiang-Hsi Kung

    • Quantum Matter Institute, University of British Columbia

Authors

  • Hsiang-Hsi Kung

    • Quantum Matter Institute, University of British Columbia

  • Adamya P Goyal

    • Department of Physics, University of Florida

  • Dmitrii Maslov

    • University of Florida
    • Department of Physics, University of Florida

  • Xueyuen Wang

    • Department of Physics, Rutgers University
    • Rutgers University, New Brunswick

  • Alexander Lee

    • Department of Physics, Rutgers University

  • Alexander Kemper

    • North Carolina State University
    • Department of Physics, North Carolina State University
    • Physics, North Carolina State University

  • Sang-Wook Cheong

    • Rutgers University
    • Department of Physics and Astronomy, Rutgers University
    • Rutgers University, New Brunswick
    • Rutgers Center for Emergent Materials and Department of Physics & Astronomy, Rutgers University
    • Center for Quantum Materials Synthesis and Department of Physics and Astronomy, Rutgers, the State University of New Jersey
    • Department of Physics, Rutgers University
    • Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, NJ
    • Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA
    • Physics, Rutgers University
    • Physics and Astronomy, Rutgers University, New Brunswick
    • Department of Physics and Astronomy, Rutgers University, New Jersey
    • Rutgers University, Physics and Astronomy, and Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science
    • RCEM, Department of Physics and Astronomy, Rutgers U.
    • Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University
    • Department of Physics and Astronomy, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA, Rutgers Center for Emergent Materials

  • Girsh E Blumberg

    • Rutgers University, New Brunswick
    • Department of Physics, Rutgers University