Investigation of supercurrent transport near the satellite Dirac point in monolayer graphene Josephson junctions

Moiré superlattice originates from the slight misalignment between stacked two-dimensional layers, providing a platform to explore new physical phenomena. In hexagonal Boron Nitride (hBN)-encapsulated graphene devices, the alignment between hBN and graphene is often overlooked. However, moiré superlattices in hBN/graphene/hBN heterostructures can form minibands manifested as satellite Dirac points (SDPs), which significantly modify the density of states and Fermi velocity. While their effects on normal-state transport have been studied, their influence on Josephson coupling remains largely unexplored.

In this work, we fabricate gate-tunable Josephson junctions using hBN-encapsulated graphene with a graphite bottom gate and NbTi superconducting contacts. The high quality of the graphite gate enables clear access to SDP features in the encapsulated graphene. By sweeping the gate voltage across the SDP, we observe a pronounced suppression of the supercurrent accompanied by an increase in the normal-state resistance, resulting in a local maximum in the I_CR_N product. These behaviors indicate a reduced Fermi velocity and enhanced phase fluctuations near the miniband edge, consistent with a diminished Josephson energy E_J. Our results demonstrate that moiré minibands can modulate not only the electronic structure but also the superconducting phase, opening a new avenue to engineer Josephson dynamics through the SDP in graphene-based Josephson junctions.