Electrochemical Na-intercalation-induced high-temperature superconductivity in FeSe

Iron-chalcogenide-based superconductors have attracted much attention due to theft relatively high superconducting transition temperatures (T-c) and their simple layered crystal structures. We have performed electrochemical co-intercalation of Na and propylene carbonate (PC) into FeSe, and successfully synthesized a new superconductor, Na-x(PC)(y)Fe2Se2, with T-c = 43 K. The type and amount of intercalated metal, and the electrolyte used in the intercalation affected the superconductivity. Our electrochemical intercalation method should be a useful tool for discovering new superconductors by controlling the intercalation conditions. (C) 2015 Elsevier B.V. All rights reserved.