Magnetic flux disorder and superconductor-insulator transition in nanohole thin films

TL;DR

This study uses numerical simulations of a Josephson-junction array model to explore how geometrical flux disorder affects the superconductor-insulator transition and resistivity in nanohole ultrathin films under a magnetic field.

Contribution

It introduces a model linking nanohole positional disorder to flux disorder and analyzes its impact on critical behavior and resistivity at the transition.

Findings

Resistivity increases with disorder for noninteger flux quanta.

Resistivity decreases with disorder for integer flux quanta.

A vortex-glass regime emerges at high flux disorder, reaching a universal resistivity value.

Abstract

We study the superconductor-insulator transition in nanohole ultrathin films in a transverse magnetic field by numerical simulation of a Josephson-junction array model. Geometrical disorder due to the random location of nanoholes in the film corresponds to random flux in the array model. Monte Carlo simulation in the path-integral representation is used to determine the critical behavior and the universal resistivity at the transition as a function of disorder and average number of flux quanta per cell, $f_o$. The resistivity increases with disorder for noninteger $ f_o$ while it decreases for integer $ f_o$, and reaches a common constant value in a vortex-glass regime above a critical value of the flux disorder $D_f^c$. The estimate of $D_f^c$ and the resistivity increase for noninteger $ f_o$ are consistent with recent experiments on ultrathin superconducting films with positional disordered nanoholes.