Probing the superconducting proximity effect in NbSe2 by scanning tunneling microscopy

Cryogenic scanning tunneling microscopy has been used as a local probe of the superconducting proximity effect across a normal metal-superconductor interface of a short coherence length superconductor. Both the topography and the local electronic density of states were measured on a superconducting NbSe2 crystal decorated with nanometer-size Au islands. The presence of a quasiparticle bound state could be inferred even when the probe was located directly on the bare NbSe2 surface near an Au island, indicating a severe depression of the pair potential inside the superconductor due to the proximity effect.