Nature of Phase Transitions of Superconducting Wire Networks in a Magnetic Field

TL;DR

This study investigates the phase transition behavior of superconducting Nb wire networks under magnetic fields, revealing scaling behavior and exponential $I$-$V$ characteristics indicative of domain-wall excitations across different incommensurability levels.

Contribution

It provides experimental evidence of continuous phase transitions and domain-wall excitations in superconducting wire networks at finite temperatures.

Findings

Scaling behavior of $I$-$V$ characteristics suggests continuous phase transition.

Exponential $I$-$V$ characteristics indicate domain-wall excitations.

Results consistent across different incommensurability levels.

Abstract

We study $I$-$V$ characteristics of periodic square Nb wire networks as a function of temperature in a transverse magnetic field, with a focus on three fillings 2/5, 1/2, and 0.618 that represent very different levels of incommensurability. For all three fillings, a scaling behavior of $I$-$V$ characteristics is found, suggesting a finite temperature continuous superconducting phase transition. The low-temperature $I$-$V$ characteristics are found to have an exponential form, indicative of the domain-wall excitations.