Preserving the Josephson Coupling of Twisted Cuprate Junctions via Tailored Silicon Nitride Circuits Boards

TL;DR

This paper introduces a cryogenic, inert assembly method using silicon nitride nanomembranes to fabricate high-quality twisted BSCCO Josephson junctions, preserving their superconducting properties and improving reproducibility.

Contribution

The study presents a novel dry, cryogenic fabrication protocol combining silicon nitride nanomembranes with pre-patterned electrodes and cryogenic stacking to enhance junction quality and reproducibility.

Findings

Achieved twist-angle-dependent Josephson coupling comparable to top devices.

Suppressed wire-bonding vibrations with asymmetric membrane designs.

Demonstrated scalable, versatile contact method for superconducting heterostructures.

Abstract

Controlled fabrication of twisted van der Waals heterostructures is essential to unlock the full potential of moire materials. However, achieving reproducibility remains a major challenge, particularly for air-sensitive materials such as $Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}$ (BSCCO), where it is crucial to preserve the intrinsic and delicate superconducting properties of the interface throughout the entire fabrication process. Here, we present a dry, inert and cryogenic assembly method that combines silicon nitride nanomembranes (NMBs) with pre-patterned electrodes and the cryogenic stacking technique (CST) to fabricate high-quality twisted BSCCO Josephson junctions (JJs). This protocol prevents thermal and chemical degradation during both interface formation and electrical contact integration. We also find that asymmetric membrane designs, such as a double cantilever, effectively suppress vibration-induced disorder due to wire bonding, resulting in sharp and hysteretic current-voltage characteristics. The junctions exhibit a twist-angle-dependent Josephson coupling with magnitudes comparable to the highest-performing devices reported to date, but achieved through a straightforward and versatile contact method, offering a scalable and adaptable platform for future applications. These findings highlight the importance of both interface and contact engineering in addressing reproducibility in superconducting van der Waals heterostructures.