title: Superconductivity in Ca-doped graphene laminates.
abstract: Despite graphene's long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures (Tc) between ≈4 and ≈6 K, with Tc's strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp.
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: J
authors.initials: J
authors.lastname: Chapman
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: Y
authors.initials: Y
authors.lastname: Su
authors.affiliation: Department of Physics and Astronomy, University College London, London, WC1E 6BT, UK.
authors.forename: C A
authors.initials: CA
authors.lastname: Howard
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: D
authors.initials: D
authors.lastname: Kundys
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: A N
authors.initials: AN
authors.lastname: Grigorenko
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.|Imdea Nanociencia, Faraday 9, 28015 Madrid, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Guinea
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: A K
authors.initials: AK
authors.lastname: Geim
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: I V
authors.initials: IV
authors.lastname: Grigorieva
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: R R
authors.initials: RR
authors.lastname: Nair