The recent discovery of superconductivity with a transition temperature (T_c) at 18 K in K_xpicene has extended the possibility of high-T_c superconductors in organic materials. Previous experience based on similar hydrocarbons, like alkali-metal doped phenanthrene, suggested that even higher transition temperatures might be achieved in alkali-metals or alkali-earth-metals doped such polycyclic-aromatic-hydrocarbons (PAHs), a large family of molecules composed of fused benzene rings. Here we report the discovery of high-T_c superconductivity at 33 K in K-doped 1,2:8,9-dibenzopentacene (C₃₀H₁₈). To our best knowledge, it is higher than any T_c reported previously for an organic superconductor under ambient pressure. This finding provides an indication that superconductivity at much higher temperature may be possible in such PAHs system and is worthy of further exploration.

© 2012 Macmillan Publishers Limited. All rights reserved