Current dependent fluctuations in a Bi$_2$Sr$_2$CuO$_{6+\delta}$ thin film

TL;DR

This study investigates how excess conductivity in a Bi$_2$Sr$_2$CuO$_{6+eta}$ thin film varies with current and doping, revealing universal behavior and sensitivity linked to granular superconductor properties.

Contribution

It demonstrates the universal current-dependent excess conductivity behavior across doping levels in a cuprate superconductor, suggesting a granular, gapless-like superconducting state.

Findings

Excess conductivity is highly sensitive to transport current.

Behavior follows a universal function of T/Tc across doping.

Results support a granular superconductor model with gapless features.

Abstract

The current dependence of the excess conductivity is measured up to $\simeq 3 T_c$ for a Bi$_2$Sr$_2$CuO$_{6+\delta}$ thin film, as a function of doping. It is found to be anomalously sensitive to the transport current and to behave as a universal function of $T/T_c$ in the whole doping range. We discuss these results in the perspective of a granular superconductor with a gapless-like behavior.