Fig. 1
Main panel: Differential conductance-versus-voltage characteristics for a planar three-dimensional N-I-n-S(s-wave) junction with various thicknesses of the normal n interlayer in the tunneling regime (D I << 1); parameters α = 2d n Δ s /(ℏv F) and β = d n/l n. Inset: Effect of the electron mean free path on the conductance spectra of a tunneling N-I-n-S(s-wave) four-layered device; the three arrows show the main elements of the peak-dip-hump structure discussed in the text