title: Experimental evidence for s-wave pairing symmetry in superconducting Cu(x)Bi2Se3 single crystals using a scanning tunneling microscope.
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 Cu(x)Bi(2)Se(3) 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 microscopy measurements of the superconducting energy gap in Cu(x)Bi(2)Se(3) 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 theory with a momentum independent order parameter, which suggests that Cu(x)Bi(2)Se(3) is a classical s-wave superconductor contrary to previous expectations and measurements.
authors.affiliation: Center for Nanoscale Science and Technology, NIST, Gaithersburg, Maryland 20899, USA and Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: Niv
authors.initials: N
authors.lastname: Levy
authors.affiliation: Center for Nanoscale Science and Technology, NIST, Gaithersburg, Maryland 20899, USA and Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, USA.
authors.forename: Tong
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Center for Nanoscale Science and Technology, NIST, Gaithersburg, Maryland 20899, USA and Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, USA and Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
authors.forename: Jeonghoon
authors.initials: J
authors.lastname: Ha
authors.affiliation: Center for Nanoscale Science and Technology, NIST, Gaithersburg, Maryland 20899, USA.
authors.forename: Fred
authors.initials: F
authors.lastname: Sharifi
authors.affiliation: Center for Nanoscale Science and Technology, NIST, Gaithersburg, Maryland 20899, USA.
authors.forename: A Alec
authors.initials: AA
authors.lastname: Talin
authors.affiliation: Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
authors.forename: Young
authors.initials: Y
authors.lastname: Kuk
authors.affiliation: Center for Nanoscale Science and Technology, NIST, Gaithersburg, Maryland 20899, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Stroscio