1. Research Laboratory for Surface Science,


2. Department of Physics,


3. Department of Chemistry, Okayama University, Okayama 700-8530, Japan


4. Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 812-8581, Japan


5. Japan Advanced Institute of Science and Technology, Ishikawa, 923-1292, Japan


6. Department of Chemistry and Chemical Biology, Gunma University, Kiryu 376-8515, Japan


7. Department of Physics, Tokyo Metropolitan University, Hachioji 192-0397, Japan

Correspondence to: Yoshihiro Kubozono¹ Correspondence and requests for materials should be addressed to Y.K. (Email: kubozono@cc.okayama-u.ac.jp).

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 compounds¹, boron-doped diamond² and—most prominently—iron arsenides such as LaO_1–xF_xFeAs (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_xpicene) shows T _c values of 7 K and 18 K, depending on the metal content. The drop of magnetization in K_xpicene solids at the transition temperature is sharp (<2 K), similar to the behaviour of Ca-intercalated graphite¹. The T _c of 18 K is comparable to that of K-intercalated C₆₀ (ref. 4). This discovery of superconductivity in K_xpicene shows that organic hydrocarbons are promising candidates for improved T _c values.

ftp://mail.ihim.uran.ru/localfiles/nature08859.pdf