Scale dependent superconductor-insulator transition

TL;DR

This study investigates how the superconductor-insulator transition in amorphous indium-oxide films depends on sample geometry, revealing that the critical resistance varies with size and shape, supporting an inhomogeneous transition scenario.

Contribution

It demonstrates that the critical sheet resistance for the transition depends on sample geometry, highlighting the importance of inhomogeneity in the transition mechanism.

Findings

Critical resistance varies with sample size and shape.

Superconductivity persists at higher resistance in wide, short samples.

Results support an inhomogeneous transition scenario.

Abstract

We study the disorder driven superconductor to insulator transition in amorphous films of high carrier-concentration indium-oxide. Using thin films with various sizes and aspect ratios we show that the `critical' sheet-resistance $R_{{\small \square}}$ depends systematically on sample geometry; superconductivity disappears when $R_{{\small \square}}$ exceeds $\approx6 $k$\Omega$ in large samples. On the other hand, wide and sufficiently short samples of the same batch exhibit superconductivity (judged by conductivity versus temperature) up to $R_{{\small \square}}$ which is considerably larger. These results support the inhomogeneous scenario for the superconductor-insulator transition.