Measurement of the Localization Length through the superconductor-insulator transition of ultrathin amorphous beryllium films

TL;DR

This study measures the localization length in ultrathin amorphous beryllium films through the superconductor-insulator transition, revealing an exponential increase in localization length with film thickness and its critical role in superconductivity onset.

Contribution

It provides a novel experimental method to determine localization length and dielectric constant in disordered superconducting films using Efros-Shklovskii behavior.

Findings

Localization length increases exponentially with film thickness.

Superconductor-insulator transition occurs when localization length equals coherence length.

Results shed light on superconductivity in strongly disordered regimes.

Abstract

Based on the Efros-Shklovskii behavior observed in electron transport and tunneling, we have determined, independently and up to a constant on the order of unity, the localization length and the dielectric constant for quench-condensed ultrathin amorphous beryllium films. As the normal-state sheet resistance of the films at 20 K is reduced with increasing film thickness, the localization length increases exponentially. The superconductor-insulator transition occurs when the localization length crosses the Ginzburg-Landau coherence length. We discuss the implication of these results on a number of issues regarding superconductivity in the strongly disordered regime.