Above-gap quasiparticle excitations in disordered graphene junctions

The behavior of superconducting graphene junctions is governed by the electrical transparency of the superconductor–graphene interface. When the transparency is reduced, a finite quasiparticle density emerges that strongly modifies charge transport. We show that graphene junctions with reduced contact transparency exhibit above-gap resistance peaks forming complex current- and magnetic field-dependent diamond-shaped interference patterns across devices with different transparencies. These features are quantitatively explained by Tomasch and McMillan–Rowell oscillations, identifying quasiparticle interference as their origin. These findings underscore the limited understanding of quasiparticle processes in diffusive superconducting junctions, which hold implications for research on superconducting quantum information architectures and their applications.