Two-Dimensional Superconductivity in Intercalated Bilayer Graphene

Abstract

We have fabricated alkali metal (Li, Rb, Cs) and alkaline-earth metal (Ca) intercalated bilayer graphene on SiC substrate, and characterized them by low-energy electron diffraction, angle-resolved photoemission spectroscopy, and 4-point-probe measurements. We observed a free-electron-like state in the center of the Brillouin zone, called “interlayer state”, as well as the folded π/π^* bands in Rb-, Cs-, and Ca-intercalated graphene, while it was absent in Li counterpart. Ca-intercalated bilayer graphene shows the zero-resistance below 4K, indicative of the two-dimensional superconductivity. These results suggest that the interlayer state plays an important role for the superconductivity in intercalated bilayer graphene.