Fig. 4: Ballistic Andreev transport.
From: Shadow-wall lithography of ballistic superconductor–semiconductor quantum devices
a False-colour SEM image of an exemplary N–S junction. The W bottom gates (brown) underneath the 100-nm-wide InSb nanowire (green) are covered by 18 nm of Al2O3 dielectric. b Differential conductance, G, as a function of source–drain voltage, VSD, and bottom tunnel-gate voltage, VTG. The so-called super gate, which controls the chemical potential of the hybrid nanowire segment, is grounded. c G versus VSD line-cuts of the data in panel b at the locations designated by the coloured lines. d Subgap conductance (green) and above-gap conductance (red) averaged over the VSD intervals designated in panel b. e GS (subgap conductance at zero bias) as a function of GN (normal-state conductance at VSD = 650 μV) together with the theoretically predicted dependence, which assumes Andreev-dominated transport in a single channel (blue line trace).
