Island formation in disordered superconducting thin films at finite magnetic fields

TL;DR

This paper investigates how superconducting islands form and evolve in disordered thin films under magnetic fields, using numerical simulations to explain experimental observations and predict new behaviors.

Contribution

It provides a detailed numerical analysis of superconducting island formation and evolution in disordered 2D superconductors under magnetic fields, including vortex pinning and Zeeman effects.

Findings

Superconducting islands form in disordered films and persist into the insulating regime.

Magnetic fields influence the size and distribution of these islands.

Islands are uncorrelated domains under Zeeman field.

Abstract

The existence of "superconducting islands" (i.e., locally confined regions with superconducting correlations) in amorphous superconducting thin films can account for numerous experimental findings. Such spatial fluctuations in the superconducting gap were indeed observed experimentally, and were shown to persist into the insulating side of the superconductor-insulator transition. In this work a detailed account on the formation and evolution of superconducting islands in disordered two-dimensional superconductors is presented, using a locally self-consistent numerical solution of the Bogoliubov-de-Gennes equations. Specifically, the formation of SC islands is demonstrated, and their evolution with an applied perpendicular magnetic field is studied in details, along with the disorder-induced vortex-pinning. Simulating the presence of a parallel Zeeman field it is demonstrated that the islands are indeed uncorrelated superconducting domains. Experimental predictions based on this analysis are presented.