Superconductivity in alkali-metal-doped picene

• Published in: Nature (London) 2010-03, Vol.464 (7285), p.76-79
• Main Authors: Mitsuhashi, Ryoji, Suzuki, Yuta, Yamanari, Yusuke, Mitamura, Hiroki, Kambe, Takashi, Ikeda, Naoshi, Okamoto, Hideki, Fujiwara, Akihiko, Yamaji, Minoru, Kawasaki, Naoko, Maniwa, Yutaka, Kubozono, Yoshihiro
• Format: Article
• Language: English
• Subjects: 639/766/119/1003; Alkali metals; Analysis; Boron nitride; Clathrate compounds; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Crystals; Dielectric films; Diffraction; Electrical conductivity; Exact sciences and technology; Graphite; Humanities and Social Sciences; Hydrocarbons; letter; Magnetic properties; Mineralogy; Molecular structure; multidisciplinary; Organic superconductors; Phase diagrams; Physical properties; Physics; Properties of type I and type II superconductors; Science; Science (multidisciplinary); Structure; Superconducting materials (excluding high-tc compounds); Superconductivity; Superconductors; Thin films; Transition temperatures
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature08859

Superconductors go organic New high-temperature superconductors continue to arrive on the scene — the most recent noteworthy additions being the iron arsenides — but there have been no new organic superconductors the past decade. Now the discovery of superconductivity at temperatures up to 18 K is reported in crystals of a simple hydrocarbon molecule doped with potassium or rubidium. The basis for the new compound is picene (C 22 H 14 ), a molecule consisting of five benzene rings sharing edges with one another, which crystallizes into an ordered molecular solid. Intercalation of the alkali metals into the crystal lattice induces metallic behaviour and superconductivity in what is normally a semiconducting material. The T c of 18 K in potassium-doped picene is high for an organic superconductor — only alkali-metal-doped C 60 achieves higher. And as picene is one of a large family of molecules based on fused benzene rings, other superconducting hydrocarbons may be awaiting discovery. The phenomenon of superconductivity continues to intrigue, and several new superconducting materials have been discovered in recent years — but in the case of organic superconductors, no new material system with a high superconducting transition temperature has been identified in the past decade. Now it has been shown that the introduction of potassium into crystals of organic molecule picene can yield superconductivity at temperatures as high as 18 K. Efforts to identify and develop new superconducting materials continue apace, motivated by both fundamental science and the prospects for application. For example, several new superconducting material systems have been developed in the recent past, including calcium-intercalated graphite compounds 1 , boron-doped diamond 2 and—most prominently—iron arsenides such as LaO 1– x F x FeAs (ref. 3 ). In the case of organic superconductors, however, no new material system with a high superconducting transition temperature ( T c ) has been discovered in the past decade. Here we report that intercalating an alkali metal into picene, a wide-bandgap semiconducting solid hydrocarbon, produces metallic behaviour and superconductivity. Solid potassium-intercalated picene (K x picene) shows T c values of 7 K and 18 K, depending on the metal content. The drop of magnetization in K x picene solids at the transition temperature is sharp (