Conductance Spectroscopy of Exfoliated Thin Flakes of NbₓBi₂Se₃
We study unconventional superconductivity in exfoliated single crystals of a promising three-dimensional (3D) topological superconductor candidate, Nb-doped Bi2Se3 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 Bi2Se3 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 Bi2Se3. Finally, we observe signatures of multiple superconducting energy gaps, which could originate from multiple Fermi surfaces reported earlier in bulk crystals.
C. Kurter et al., "Conductance Spectroscopy of Exfoliated Thin Flakes of NbₓBi₂Se₃," Nano Letters, vol. 19, no. 1, pp. 38-45, American Chemical Society (ACS), Jan 2019.
The definitive version is available at https://doi.org/10.1021/acs.nanolett.8b02954
Keywords and Phrases
Andreev reflection spectroscopy; doped topological insulators; exfoliated Nb x Bi 2 Se 3; Majorana bound states; p-wave pairing symmetry; Topological superconductivity
International Standard Serial Number (ISSN)
Article - Journal
© 2019 American Chemical Society (ACS), All rights reserved.
01 Jan 2019