Characterizing the insulator adjacent to the superconductor in Bi$_2$Sr$_{2-x}$La$_{x}$CuO$_{6+\delta}$ ($x=0.3$)

TL;DR

This study investigates the transport noise properties near the superconductor-insulator transition in a La-doped bismuth cuprate thin film, revealing a superconductor embedded in a strong insulator with 2D variable range hopping characteristics.

Contribution

It provides new insights into the nature of the insulator adjacent to the superconductor in Bi-based cuprates, highlighting the role of metallic inclusions and 2D hopping behavior.

Findings

Superconductor embedded in a strong insulator with 2D variable range hopping.

Weak insulator behavior attributed to metallic inclusions.

Transport properties consistent with a superconductor-metal-insulator scenario.

Abstract

The time-averaged and low--frequency noise transport properties were investigated in the vicinity of the superconductor--insulator transition for a Bi$_2$Sr$_{2-x}$La$_{x}$CuO$_{6+\delta}$ ($x=0.3$) thin film. The results are consistent with a superconductor (metal) embedded in a strong insulator, the latter showing two-dimensional variable range hopping properties. The weak insulator behavior -- if any -- is attributed to the metallic inclusions only.