Spatially resolved tunneling spectroscopy of superconducting wires with artificial pinning centers

We used scanning tunneling microscopy and spectroscopy to study with nanometer resolution the spatial variation of superconductivity in the vicinity of the interface between normal and superconductor regions. The samples were novel superconducting wires consisting of ordered arrays of sub-micron diameter normal metal filaments, either Cu or Ni, embedded in a NbTi superconducting matrix. By taking topographic images simultaneously with current–voltage curves, we obtain information about the local quasi-particle density of states on both sides of the interface.