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

TL;DR

This study uses scanning tunneling spectroscopy to reveal that inhomogeneities in the superconducting gap increase with disorder in Titanium Nitride films, indicating local superconductivity persists near the superconductor-insulator transition.

Contribution

It demonstrates that local superconductivity survives across the disorder-driven superconductor-insulator transition, highlighting the role of inhomogeneities in disordered superconductors.

Findings

Superconducting gap $$ becomes more inhomogeneous with disorder.

Superconducting critical temperature $T_c$ decreases towards zero as disorder increases.

The ratio $/T_c$ increases with disorder, indicating enhanced inhomogeneity.

Abstract

Scanning tunneling spectroscopy at very low temperature on homogeneously disordered superconducting Titanium Nitride thin films reveals strong spatial inhomogeneities of the superconducting gap $\Delta$ 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 $\Delta$, and growth of the $\Delta/T_c$ ratio. These findings suggest that local superconductivity survives across the disorder-driven superconductor-insulator transition.