Conductance Spectroscopy of Exfoliated Thin Flakes of Nb x Bi 2 Se 3

C. Kurter, A. D.K. Finck, E. D. Huemiller, J. Medvedeva, A. Weis, J. M. Atkinson, Y. Qiu, L. Shen, S. H. Lee, T. Vojta, P. Ghaemi, Y. S. Hor, D. J. Van Harlingen

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Abstract

We study unconventional superconductivity in exfoliated single crystals of a promising three-dimensional (3D) topological superconductor candidate, Nb-doped Bi 2 Se 3 through differential conductance spectroscopy and magneto-transport. The strong anisotropy of the critical field along the out-of-plane direction suggests that the thin exfoliated flakes are in the quasi-2D limit. Normal metal-superconductor (NS) contacts with either high or low transparencies made by depositing gold leads onto Nb-doped Bi 2 Se 3 flakes both show significant enhancement in zero bias conductance and coherence dips at the superconducting energy gap. Such behavior is inconsistent with conventional Blonder-Tinkham-Klapwijk theory. Instead, we discuss how our results are consistent with p-wave pairing symmetry, supporting the possibility of topological superconductivity in Nb-doped Bi 2 Se 3 . Finally, we observe signatures of multiple superconducting energy gaps, which could originate from multiple Fermi surfaces reported earlier in bulk crystals.

Original languageEnglish (US)
Pages (from-to)38-45
Number of pages8
JournalNano letters
Volume19
Issue number1
DOIs
StatePublished - Jan 9 2019

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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    Kurter, C., Finck, A. D. K., Huemiller, E. D., Medvedeva, J., Weis, A., Atkinson, J. M., Qiu, Y., Shen, L., Lee, S. H., Vojta, T., Ghaemi, P., Hor, Y. S., & Van Harlingen, D. J. (2019). Conductance Spectroscopy of Exfoliated Thin Flakes of Nb x Bi 2 Se 3 Nano letters, 19(1), 38-45. https://doi.org/10.1021/acs.nanolett.8b02954