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.



Research Center/Lab(s)

Center for High Performance Computing Research

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)

1530-6984; 1530-6992

Document Type

Article - Journal

Document Version


File Type





© 2019 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Jan 2019