Single-particle proximity effect between superconductors through a tunneling barrier

Abstract

The single-particle proximity effect between superconductors seperated by a tunneling barrier is observed experimentally in double tunneling junctions. The dependence of the single-particle proximity effect of a small voltage difference across the tunneling barrier is measured. An energy region  E < Δ appears to be typical for this effect because in this region the proximity-effect-induced superconducting density-of-states function is not smeared. It is possible to describe the single-particle proximity effect between superconductors within the extended McMillan tunneling model of the superconducting proximity effect.