Disordered Superconductivity in Graphene Oxide Nanocomposite Systems

We introduce a novel system comprising transition metal (Palladium or Platinum) nanoparticles randomly intercalated in a regularly spaced graphene oxide bilayer [ Sugak et. al. ‘Controlling the spacing of the linked graphene oxide system with dithiol linkers under confinement’, Nanoscale Advances, 5, 4553, (2023)].   Samples synthesized at pressures of ~5 GPa and exposed to a hydrogen source at high temperature (1000°C) showed superconductivity with T_c’s ranging from 1.5 to 5 K depending on the nanoparticle type. In contrast, superconductivity in Moire-based graphene systems occur with a T_c of a few hundred millikelvin.  Superconductivity is retained when the samples were brought back to ambient pressures without any complex pressure quenching protocols. We use SQUID magnetometry, resistance and specific heat measurements to probe the transition. The randomly distributed nanoparticles had diameters ~ 5 nm but correlation lengths determined from H_c2 measurements were around 200 nm which points to the significant role of the linked graphene oxide in enabling and sustaining superconductivity. X-ray diffraction measurements performed at the Argonne National Lab and high-resolution TEM measurements will be presented to elucidate the structural details of the samples . We will discuss how these details help to understand the emergence of superconductivity in these highly disordered linked graphene oxide systems.