Ballistic graphene- Josephson junction in high parallel magnetic field

Einav Grynszpan, Ayelet Zalic, Pradheesh Ramachandran, Takashi Taniguchi, Kenji Watanabe, Anna Keselman and Hadar Steinberg

Planar graphene- Josephson junctions can support supercurrents at high in-plane magnetic fields ( ) due to the robust superconductivity in thin , protected from both orbital and spin-driven decay by a combination of atomic thickness and Ising spin orbit coupling. We fabricate and characterize a clean, flat graphene- junction encapsulated in hexagonal boron nitride. The junction is ballistic, exhibiting Fabry–Pérot oscillations of the critical current, and supports very high critical current densities. The junction is remarkably robust to both in-plane and out-of-plane magnetic fields, and exhibits a clear ballistic Josephson effect up to the maximally available in-plane field of 8 T. We model the suppression of the critical current using a tight-binding model, accounting for the large overlap area between the and graphene. We find that the suppression is governed by both the Zeeman splitting of Andreev bound states and by the flux threading the van-der-Waals gap that separates graphene from the leads.

Grynszpan, E., Zalic, A., Ramachandran, P., Taniguchi, T., Watanabe, K., Keselman, A., & Steinberg, H. (2025). Ballistic graphene-NbSe 2 Josephson junction in high parallel magnetic field. 2D Materials, 12(4), 041004. https://doi.org/10.1088/2053-1583/ae07fa