Flux Flow Instabilities in Microstructured Amorphous Nb0.7Ge0.3 Thin Films

TL;DR

This study investigates flux flow instabilities in amorphous Nb0.7Ge0.3 thin films, demonstrating the applicability of Larkin-Ovchinnikov theory near Tc and identifying electron heating effects at lower temperatures.

Contribution

It provides a detailed experimental analysis of flux flow instabilities in amorphous NbGe films, highlighting different mechanisms near Tc and at lower temperatures.

Findings

Larkin-Ovchinnikov theory describes flux flow near Tc

Electron heating causes flux flow instability at lower temperatures

Scaling analysis confirms different instability mechanisms

Abstract

We report measurements of the electric field vs. current density [E(J] characteristics in the mixed state of amorphous Nb0.7Ge0.3 microbridges. Close to the transition temperature Tc the Larkin-Ovchinnikov theory of nonlinear flux flow and the related instability describes the data quantitatively up to ~ 70% of the upper critical magnetic field Bc2 and over a wide electric field range. At lower temperatures the nonlinearities of E(J)can be described by electron heating which reduces Bc2 and leads to a second type of flux flow instability, as shown by a scaling analysis of the high-dissipation data.