Spectroscopic evidence for strong correlations between local superconducting gap and local Altshuler-Aronov density of states suppression in ultrathin NbN films

Abstract

In metallic films, disorder localizes the electronic wave functions. A consequence is that electronic screening often diminishes. In this situation, a characteristic signature develops in the electronic density of states: a large depletion appears at the Fermi level, an effect predicted by Altshuler and Aronov. Here, the authors show that this depletion presents nanoscale spatial variations in NbN thin films that are spatially strongly correlated to the local superconducting energy gap. This provides a direct link between local Coulombic effects and local superconducting properties.