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

•Nax(PC)yFe2Se2, with Tc = 43 K has been synthesized•The co-intercalation of Na and PC into FeSe greatly increases the distance between Se layers, leading to the high Tc•The electrochemical intercalation method, in which various combinations of metal and solvent are possible, allows for the synthesis of new iron-chalcogenide-based superconductors.

Iron-chalcogenide-based superconductors have attracted much attention due to their relatively high superconducting transition temperatures (Tc) 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, Nax(PC)yFe2Se2, with Tc = 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.