Ballistic graphene-NbSe₂Josephson junction in high parallel magnetic field

Planar graphene-NbSe₂ Josephson junctions can support supercurrents at high in-plane magnetic fields (B ∥) due to the robust superconductivity in thin NbSe₂, 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-NbSe₂ junction encapsulated in hBN. 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 NbSe₂ 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 NbSe₂ leads.