4 research outputs found
Robust Fabry-Perot interference in dual-gated BiSe devices
We study Fabry-Perot interference in hybrid devices, each consisting of a
mesoscopic superconducting disk deposited on the surface of a three-dimensional
topological insulator. Such structures are hypothesized to contain protected
zero modes known as Majorana fermions bound to vortices. The interference
manifests as periodic conductance oscillations of magnitude .
These oscillations show no strong dependence on bulk carrier density or sample
thickness, suggesting that they result from phase coherent transport in surface
states. However, the Fabry-Perot interference can be tuned by both top and back
gates, implying strong electrostatic coupling between the top and bottom
surfaces of topological insulator.Comment: 5 pages, 3 figures. Accepted by Appl. Phys. Let
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