Realization of High-temperature Superconductivity in Nano-carbon Materials and Its Application.

摘要

Superconductivity (SC) is one of the hottest topics in condensed matter physics and also for application to zeroemission energy system. In particular, carbon-based superconductors have attracted significant attention for high transition temperature (Tc). The present work attempts to realize high-Tc SC in thin films of carbon nanotubes (CNTs) by using ionic-gel (liquid) gating. Extremely high carrier density in CNT films caused by the optimized ionicgel gate allows possible Tc as high as 48K, while reproducibility is poor due to non-uniform ionization in the gel. In contrast, reproducible abrupt-resistance drop at T ~47K is observed by ionic-liquid gating, whereas magnitude of the drop is small, but further optimization promises high-Tc SC. On the other hand, edge spin of graphene can be also a good candidate for causing SC. Applying ionic-liquid gate voltage to graphene nanomesh (GNM) allows reconfirmation of induced polarized-spins at pore edges with anti-ferromagnetic (AFM) spin alignment. Moreover, tunnel magnetoresistance structure fabricated utilizing ferromagnetic GNM reveals that AFM alignment between pore-edge spins and spins of Co electrode is possible. AFM spin alignment promises possible SC based on graphene edge spins.