Superconductivity above 30 K in alkali-metal-doped hydrocarbon

The recent discovery of superconductivity with a transition temperature (Tc) at 18 K in Kxpicene has extended the possibility of high-Tc 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-Tc superconductivity at 33 K in K-doped 1,2:8,9-dibenzopentacene (C30H18). To our best knowledge, it is higher than any Tc 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

How insects survive the cold: molecular mechanisms - a review

Insects vary considerably in their ability to survive low temperatures. The tractability of these organisms to experimentation has lead to considerable physiology-based work investigating both the variability between species and the actual mechanisms themselves. This has highlighted a range of strategies including freeze tolerance, freeze avoidance, protective dehydration and rapid cold hardening, which are often associated with the production of specific chemicals such as antifreezes and polyol cryoprotectants. But we are still far from identifying the critical elements behind over-wintering success and how some species can regularly survive temperatures below -20°C. Molecular biology is the most recent tool to be added to the insect physiologist’s armoury. With the public availability of the genome sequence of model insects such as Drosophila and the production of custom-made molecular resources, such as EST libraries and microarrays, we are now in a position to start dissecting the molecular mechanisms behind some of these well-characterised physiological responses. This review aims to provide a state of the art snapshot of the molecular work currently being conducted into insect cold tolerance and the very interesting preliminary results from such studies, which provide great promise for the future

Bulk superconductivity at 38 K in a molecular system

C60-based solids1 are archetypal molecular superconductors with transition temperatures (Tc) as high as 33 K (refs 2–4). Tc of face-centred-cubic (f.c.c.) A3C60 (A=alkali metal) increases monotonically with inter C60 separation, which is controlled by the A+ cation size. As Cs+ is the largest such ion, Cs3C60 is a key material in this family. Previous studies revealing trace superconductivity in CsxC60 materials have not identified the structure or composition of the superconducting phase owing to extremely small shielding fractions and low crystallinity. Here, we show that superconducting Cs3C60 can be reproducibly isolated by solvent-controlled synthesis and has the highest Tc of any molecular material at 38 K. In contrast to other A3C60 materials, two distinct cubic Cs3C60 structures are accessible. Although f.c.c. Cs3C60 can be synthesized, the superconducting phase has the A15 structure based uniquely among fullerides on body-centred-cubic packing. Application of hydrostatic pressure controllably tunes A15 Cs3C60 from insulating at ambient pressure to superconducting without crystal structure change and reveals a broad maximum in Tc at 7 kbar. We attribute the observed Tc maximum as a function of inter C60separation—unprecedented in fullerides but reminiscent of the atom-based cuprate superconductors—to the role of strong electronic correlations near the metal–insulator transition onset