Clarifying superconducting proximity effects in topological insulating (Bi<sub>1-x</sub>Sb<sub>x</sub>)<sub>2</sub>Te<sub>3</sub> films on niobium

ORAL

Abstract

Coupling a topological insulator (TI) with an s-wave superconductor (SC) can initiate p-wave-like pairing in the nontrivial surface states. However, this proximity-induced pairing is still not well understood and challenging to realize, possibly due to a short superconducting coherence length and/or Fermi surface/lattice mismatch at the TI/SC interface. Using a novel cleavage-based “flip-chip” method, we have successfully prepared single-crystalline (Bi1-xSbx)2Te3 thin films with a predetermined thickness (2-5 quintuple layers) on bulk Nb substrate. By carefully tuning the composition x, we confirm using angle-resolved photoemission spectroscopy (ARPES) that the Fermi level lies in the band gap for all (Bi1-xSbx)2Te3 films, thus yielding a lightly n-doped TI on a SC even in the thin-film limit. Proximity-induced superconducting gaps in these samples are measured by ultrahigh-resolution laser ARPES. The results will be compared with those from prior studies of heavily n-doped TI films on Nb. Our study helps to reveal the mechanisms of proximity-induced pairing in TIs and also underscores the limitations of using the proximity effect to realize topological superconductivity.

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Presenters

  • Joseph Hlevyack

    • Department of Physics, University of Illinois at Urbana-Champaign
    • University of Illinois at Urbana-Champaign

Authors

  • Joseph Hlevyack

    • Department of Physics, University of Illinois at Urbana-Champaign
    • University of Illinois at Urbana-Champaign

  • Sahand Najafzadeh

    • Institute for Solid State Physics, University of Tokyo

  • Meng-Kai Lin

    • Department of Physics, University of Illinois at Urbana-Champaign
    • University of Illinois at Urbana-Champaign

  • Takahiro Hashimoto

    • Institute for Solid State Physics, University of Tokyo

  • Akihiro Tsuzuki

    • Institute for Solid State Physics, University of Tokyo

  • Tsubaki Nagashima

    • Institute for Solid State Physics, University of Tokyo

  • Weilu Zhang

    • Shangzhi University

  • Akiko Fukushima

    • Institute for Solid State Physics, University of Tokyo

  • Yang Bai

    • University of Illinois at Urbana-Champaign

  • Peng Chen

    • Shanghai Jiao Tong University

  • Ro-Ya Liu

    • University of Illinois at Urbana-Champaign

  • Yao Li

    • University of Illinois at Urbana-Champaign

  • David Floetotto

    • Center for Soft Nanoscience, University of Muenster

  • José Avila

    • Synchrotron SOLEIL
    • Synchrotron SOLEIL and Universite Paris-Saclay
    • SOLEIL

  • James N Eckstein

    • University of Illinois at Urbana-Champaign

  • Kozo Okazaki

    • Institute for Solid State Physics, University of Tokyo
    • Univ of Tokyo-Kashiwanoha

  • Shik Shin

    • Univ of Tokyo
    • University of Tokyo
    • Institute for Solid State Physics, University of Tokyo
    • Univ of Tokyo-Kashiwanoha
    • Institute for Solid State Physics, The University of Tokyo

  • Tai-Chang Chiang

    • Department of Physics, University of Illinois at Urbana-Champaign
    • University of Illinois at Urbana-Champaign