Scanning tunneling microscopy of superconducting topological surface   states in Bi$_2$Se$_3$
  In this paper we present scanning tunneling microscopy of a large $\textrm{Bi}_2\textrm{Se}_3$ crystal with superconducting PbBi islands deposited on the surface. Local density of states measurements are consistent with induced superconductivity in the topological surface state with a coherence length of order 540 nm. At energies above the gap the density of states exhibits oscillations due to scattering caused by a nonuniform order parameter. Strikingly, the spectra taken on islands also display similar oscillations along with traces of the Dirac cone, suggesting an inverse topological proximity effect. 
Ian M. Dayton, Nicholas Sedlmayr, Victor Ramirez, Thomas Chasapis,   Reza Loloee, Mercouri Kanatzidis, Alex Levchenko, and S...
cond-mat.supr-con cond-mat.mes-hall