Ballistic graphene-NbSe ₂ Josephson junction in high parallel magnetic field

Abstract Planar graphene-NbSe 2 Josephson junctions can support supercurrents at high in-plane magnetic fields ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>B</mml:mi> <mml:mo>∥</mml:mo> </mml:msub> </mml:mrow> </mml:math> ) due to the robust superconductivity in thin NbSe 2 , 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-NbSe 2 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 NbSe 2 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 NbSe 2 leads.