Disorder-Induced Inhomogeneities of the Superconducting State Close to the Superconductor-Insulator Transition

Abstract

Scanning tunneling spectroscopy at very low temperature on homogeneously disordered superconducting Titanium Nitride thin films reveals strong spatial inhomogeneities of the superconducting gap $Δ$ in the density of states. Upon increasing disorder, we observe suppression of the superconducting critical temperature $T_c$ towards zero, enhancement of spatial fluctuations in $Δ$, and growth of the $Δ/T_c$ ratio. These findings suggest that local superconductivity survives across the disorder-driven superconductor-insulator transition.

4 pages, 3 figures. Minor changes. Accepted for publication in Phys. Rev. Lett