title: Formation of Nanofoam carbon and re-emergence of Superconductivity in compressed CaC6.
abstract: Pressure can tune material's electronic properties and control its quantum state, making some systems present disconnected superconducting region as observed in iron chalcogenides and heavy fermion CeCu2Si2. For CaC6 superconductor (Tc of 11.5 K), applying pressure first Tc increases and then suppresses and the superconductivity of this compound is eventually disappeared at about 18 GPa. Here, we report a theoretical finding of the re-emergence of superconductivity in heavily compressed CaC6. The predicted phase III (space group Pmmn) with formation of carbon nanofoam is found to be stable at wide pressure range with a Tc up to 14.7 K at 78 GPa. Diamond-like carbon structure is adhered to the phase IV (Cmcm) for compressed CaC6 after 126 GPa, which has bad metallic behavior, indicating again departure from superconductivity. Re-emerged superconductivity in compressed CaC6 paves a new way to design new-type superconductor by inserting metal into nanoporous host lattice.
authors.affiliation: 1] School of Physics and Electronic Engineering, Jiangsu Normal University, 221116, Xuzhou, People's Republic of China [2] Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden.
authors.forename: Yan-Ling
authors.initials: YL
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Luo
authors.forename: Xiao-Jia
authors.initials: XJ
authors.lastname: Chen
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zeng
authors.forename: Hai-Qing
authors.initials: HQ
authors.lastname: Lin
authors.forename: Rajeev
authors.initials: R
authors.lastname: Ahuja