Vortex Pinning in Niobium covered by a thin polycrystalline Gold

TL;DR

This study investigates vortex pinning in niobium films covered with a thin polycrystalline gold layer, revealing a highly transparent interface and demonstrating that gold capping preserves superconductivity while enabling vortex imaging.

Contribution

It provides new insights into vortex pinning mechanisms and interface transparency in Nb/Au heterostructures using scanning tunneling microscopy and spectroscopy.

Findings

Gold capping preserves Nb superconductivity.

Vortex pinning occurs at the polycrystalline gold grain boundaries.

The Nb/Au interface is highly transparent, beneficial for device applications.

Abstract

Owing to its superconducting properties, Niobium (Nb) is an excellent candidate material for superconducting electronics and applications in quantum technology. Here we perform scanning tunneling microscopy and spectroscopy experiments on Nb films covered by a thin gold (Au) film. We investigate the minigap structure of the proximitized region and provide evidence for a highly transparent interface between Nb and Au, beneficial for device applications. Imaging of Abrikosov vortices in presence of a perpendicular magnetic field is reported. The data show vortex pinning by the granular structure of the polycrystalline Au film. Our results show robust and homogeneous superconducting properties of thin Nb film in the presence of a gold capping layer. The Au film not only protects the Nb from surface oxidation but also preserves its excellent superconducting properties.