Critical temperatures and critical currents of wide and narrow quasi-one-dimensional superconducting aluminum structures in zero magnetic field

TL;DR

This study measures critical temperatures and currents in aluminum superconducting structures, revealing that narrower structures have lower critical parameters and exhibit Josephson junction behavior near transition temperatures.

Contribution

It is the first to demonstrate the dependence of critical temperature and current on structure width and to identify Josephson junction formation at specific temperatures.

Findings

Narrower structures have lower critical temperatures and currents.

Switching current behavior fits two models depending on temperature.

Josephson SNS junctions form near the N-S transition temperature.

Abstract

We measured the critical temperatures and critical switching and retrapping currents of wide and narrow thin-film quasi-one-dimensional superconducting aluminum structures of the same thickness in zero magnetic field. For the first time, we found that the narrower the structure, the lower the critical temperature and critical current density in the structure. Probably, the influence of depairing centers that are on dirty longitudinal boundaries of the structure, is the stronger than the narrower the structure. It is found for the first time that, in most cases, the temperature-dependent switching critical current in both structures is approximated by two functions. At temperatures below the temperature corresponding to the bottom of the resistive N-S transition of structures, the switching critical current is described by the Kupriyanov-Lukichev theory. At temperatures close to the top of the N-S transition, the switching current is linear with temperature and coincides with the critical Josephson current. At these temperatures, Josephson SNS junctions are formed in structures.