Tuning superconductivity utilizing induced strain in a 2D confined system with encapsulated palladium nanoparticles via effect of confinement and transient pressurization*

Significant advancements in nanotechnology, particularly in enhancing essentials for quantum information systems and superconductivity, are due to deeper understanding of nanoparticle behavior within confined spaces and under high pressure. Induced pressure can stabilize structures formed or transformed at lower pressure conditions, leading to the emergence of novel phases and properties. It is yet known how these pressure-induced effects on superconductivity in 2D materials is preserved when the pressure is relieved. Here, we present how a strained and linked confined 2D graphene system raises the superconducting critical temperature of in situ generated palladium (Pd) nanoparticles formed at high pressure, functioning as a nanoscale reactor at high pressures. We reproducibly retained superconducting properties when the material was depressurized to ambient conditions. This phenomenon occurs due to an "induced pressure" created by strain on the 2D confined graphene system via encapsulation of Pd nanoparticles trapped between the linked and flexible graphene oxide layers and transient pressurization up to 25 GPa. After 5 GPa pressurization at 1100°C, the system showed a reproducible superconducting transition at 2.3K, while at 900°C the system measured a superconducting transition at 5K and 10K. These superconducting transitions are measured utilizing SQUID after the pressure is released, meaning that these properties formed then can be used in practical applications under lower pressure requirements. HRTEM, XPS, and Raman were performed to identify the phase transition, morphological changes, and structural transformation responsible for the superconductivity. This 2D graphene-based confined system with induced strain via transient pressurization offers a new platform to be utilized for emergent superconductive materials.