title: Superconducting Calcium-Intercalated Bilayer Graphene.
abstract: We report the direct evidence for superconductivity in Ca-intercalated bilayer graphene C6CaC6, which is regarded as the thinnest limit of Ca-intercalated graphite. We performed the electrical transport measurements with the in situ 4-point-probe method in ultrahigh vacuum under zero- or nonzero-magnetic field for pristine bilayer graphene, Li-intercalated bilayer graphene (C6LiC6) and C6CaC6 fabricated on SiC substrate. We observed that the zero-resistance state occurs in C6CaC6 with the onset temperature (T(c)(onset)) of 4 K, while the T(c)(onset) is gradually decreased upon applying the magnetic field. This directly proves the superconductivity origin of the zero resistance in C6CaC6. On the other hand, both pristine bilayer graphene and C6LiC6 exhibit nonsuperconducting behavior, suggesting the importance of intercalated atoms and its species to drive the superconductivity.
authors.affiliation: Department of Physics, University of Tokyo , Tokyo 113-0033, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Ichinokura
authors.affiliation: WPI Research Center, Advanced Institute for Materials Research, Tohoku University , Sendai 980-8577, Japan.
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Sugawara
authors.affiliation: Department of Physics, University of Tokyo , Tokyo 113-0033, Japan.
authors.forename: Akari
authors.initials: A
authors.lastname: Takayama
authors.affiliation: WPI Research Center, Advanced Institute for Materials Research, Tohoku University , Sendai 980-8577, Japan.|Department of Physics, Tohoku University , Sendai 980-8578, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Takahashi
authors.affiliation: Department of Physics, University of Tokyo , Tokyo 113-0033, Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Hasegawa
keywords: carbon; electrical transport; graphene; graphite-intercalation-compound; semiconductor surface; superconductivity; ultrahigh vacuum