Geometry Effects on Switching Currents in Superconducting Ultra Thin Films

TL;DR

This paper investigates how the geometry of ultra-thin superconducting films influences their switching currents and vortex dynamics, which are crucial for optimizing superconducting device performance.

Contribution

It provides experimental insights into the impact of geometry on switching currents in ultra-thin NbN and NbTiN films, highlighting material-specific behaviors at low magnetic fields.

Findings

Different behaviors observed in NbN and NbTiN films at low magnetic fields.

Geometry significantly influences the transport properties of ultra-thin superconducting films.

Material-dependent vortex dynamics affect the stability and switching currents.

Abstract

Vortex dynamics is strongly connected with the mechanisms responsible for the photon detection of superconducting devices. Indeed, the local suppression of superconductivity by photon absorption may trigger vortex nucleation and motion effects, which can make the superconducting state unstable. In addition, scaling down the thickness of the superconducting films and/or the width of the bridge geometry can strongly influence the transport properties of superconducting films, e.g. affecting its critical current as well as its switching current into the normal state. Understanding such instability can boost the performances of those superconducting devices based on nanowire geometries. We present an experimental study on the resistive switching in NbN and NbTiN ultra-thin films with a thickness of few nanometers. Despite both films were patterned with the same microbridge geometry, the two superconducting materials show different behaviors at very low applied magnetic fields. A comparison with other low temperature superconducting materials outlines the influence of geometry effects on the superconducting transport properties of these materials particularly useful for devices applications.