Two-stage dissipation in a superconducting microbridge: Experiment and modeling

TL;DR

This paper investigates the two-step dissipation behavior in a superconducting microbridge using thermal imaging and models the phenomenon considering local inhomogeneities, revealing hot spot formation and global dissipation onset.

Contribution

It provides experimental evidence and a simple inhomogeneous superconductor model explaining the two-step dissipation process in superconducting microbridges.

Findings

First voltage step corresponds to local hot spot formation.

Second voltage step indicates global dissipation across the bridge.

Model successfully explains experimental observations.

Abstract

Using fluorescent microthermal imaging we have investigated the origin of "two-step" behavior in I-V curves for a current-carrying YBa_2Cu_3O_x superconducting bridge. High resolution temperature maps reveal that as the applied current increases the first step in the voltage corresponds to local dissipation (hot spot), whereas the second step is associated with onset of global dissipation throughout the entire bridge. A quantitative explanation of the experimental results is provided by a simple model for an inhomogeneous superconductor, assuming that the hot spot nucleates at a location with slightly depressed superconducting properties.