YBa$_2$Cu$_3$O$_7$ nano-constriction Josephson junctions and SQUIDs fabricated by focused helium-ion-beam irradiation

TL;DR

This paper demonstrates a method to create nanoscale Josephson junctions and SQUIDs in YBa2Cu3O7 thin films using focused helium-ion-beam irradiation, enabling new superconducting device applications.

Contribution

It introduces a novel technique to fabricate superconducting nanostructures in YBCO via helium-ion-beam irradiation, preserving crystallinity while controlling superconductivity.

Findings

Successfully fabricated YBCO Josephson junctions with helium-ion irradiation.

Integrated these junctions into SQUIDs and THz detectors.

Achieved nanoscale control over superconducting properties.

Abstract

By focused $30\,\mathrm{keV}$ He ion beam irradiation, epitaxially grown YBa$_2$Cu$_3$O$_7$ (YBCO) thin films can be driven from the superconducting to the insulating state with increasing irradiation dose. A properly chosen dose suppresses superconductivity down to $4\,\mathrm{K}$, while crystallinity is still preserved. With this approach we create areas of normal-conducting YBCO that can be used to define resistively shunted constriction-type Josephson junctions (cJJs) on the nanometer scale. We also demonstrate that the fabricated cJJs can be incorporated in direct current superconducting quantum interference devices and can be used as detector junctions in THz antennas.