Local Measurements of the Superconducting Pairing Symmetry in CuxBi2Se3

Abstract

Topological superconductors represent a newly predicted phase of matter that is topologically distinct from conventional superconducting condensates of Cooper pairs. As a manifestation of their topological character, topological superconductors support solid-state realizations of Majorana fermions at their boundaries. The recently discovered superconductor CuxBi2Se3 has been theoretically proposed as an odd-parity superconductor in the time-reversal-invariant topological superconductor class and point-contact spectroscopy measurements have reported the observation of zero-bias conductance peaks corresponding to Majorana states in this material. Here we report scanning tunneling spectroscopy (STS) measurements of the superconducting energy gap in CuxBi2Se3 as a function of spatial position and applied magnetic field. The tunneling spectrum shows that the density of states at the Fermi level is fully gapped without any in-gap states. The spectrum is well described by the Bardeen-Cooper-Schrieffer (BCS) theory with a momentum independent order parameter, which suggests that Cu0.2Bi2Se3 is a classical s-wave superconductor contrary to previous expectations and measurements.

References in corpus (3)

• Bulk superconducting phase with a full energy gap in the doped topological insulator Cu_xBi_2Se_3
• Electrochemical synthesis and superconducting phase diagram of Cu_xBi2Se3
• Point-contact Andreev reflection spectroscopy of candidate topological superconductor Cu0.25Bi2Se3

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