Hydrocarbon superconductor created

Hydrocarbon superconductor created
Molecular structure, crystal structure and physical appearance of picene. Photographs show pristine picene (top; white) and Kxpicene (bottom; black). Image credit: Nature.
(PhysOrg.com) -- Scientists from Okayama University in Japan have discovered that the hydrocarbon picene can be made to superconduct when potassium atoms are interspersed with the picene crystals and the doped picene is cooled.

Electricity flows through a superconductor with no resistance when the material is chilled to below a (Tc). The phenomenon was discovered in 1911 by Dutch scientist Heike Kamerlingh Onnes, who demonstrated the lack of resistance by creating an in a closed loop of a mercury superconductor. After the driving potential was removed, the current continued to flow even on the journey from the Netherlands to England.

Picene (C22H14) is an organic compound found occurring naturally in coal tar, and in residues of the petroleum refining process. It is usually a semiconductor, but the researchers, led by Yoshihiro Kubozono, found that when synthesized picene is doped (intercalated) with atoms of an alkali such as or potassium it became a superconductor with a Tc of 18 kelvin (-255 degrees Celsius) or below, which is a relatively high temperature for superconductors. Professor Kubozono said picene is the first example of a superconductor, although scientists have been able to create superconductors of the carbon compound fullerene (C60) doped with potassium.

The picene molecule resembles five benzene rings joined in a staggered line, and is a flat molecule that stacks into layers to form crystals. The researchers cooked picene with potassium, which forced the alkali atoms between the layers and improved its conductivity in planes parallel to the layers.

The researchers are now trying other metals with picene, including and sodium, and are testing other hydrocarbons for superconductivity. Their research paper is published in Nature. A commentary in the journal, by Kosmas Prassides of Durham University, described the work as "exciting news for superconductivity researchers". He predicted it would stimulate more work on hydrocarbons to confirm the work of the Japanese researchers and to find other hydrocarbons that can be coaxed into becoming .

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More information: Superconductivity in alkali-metal-doped picene, Ryoji Mitsuhashi et al., Nature 464, 76-79 (4 March 2010). doi:10.1038/nature08859

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Mar 10, 2010
Superconductivity does not like warmth. Warmth does nothing else then shakes atoms. From that can be concluded that superconductivity does not like shaking. This mean for high temperature superconductivity shaking must be suppressed. There are only two possibilities to suppress atoms thermal motion: first is using strong chemical bounds (suppress amplitude but increase speed) and second is using really heavy atoms (suppress both amplitude and speed). Anybody ever tray to use depleted Uranium for doping?

Mar 10, 2010
@taka -

your incorrect statements must be because English is not your first language (that's not a criticism of your English, just of your poor understanding of superconductivity). Superconductive states MUST be preceded by specific types of phonon propagation, which are, BY DEFINITION, quantized vibrations of the crystal lattice. The trick is to figure out how to manage these vibrations and, most importantly, to figure out WHY phonon propagation is so critical to superconductivity @ T_c.

Mar 11, 2010
I made no assumptions of how it works. Just pure logic. Sometimes it is better to abstract from details and tray to see the big picture. And it is not in contradiction with phonons, for them the thermal movement may be disturbing noise. But it leaves the question of why it switches on and off so rapidly when temperature changes, thermal movement changes gradually and atoms do not change its arrangement! And yes, English is not my first language.

Mar 12, 2010
While its true that most superconductivity has a very sharp cutoff, other properties such as current carrying capacity do not. Generally speaking, thermal disruption causes defect growth (vortexes), limiting the amount of material available to super conduct (and current carrying capacity), until at the cutoff the defects completely overwhelm the material.

Mar 22, 2010
Existence of quantified phonons may prevent electrons to transform its energy into heat. If electron moves near atom it influence atom by its e field and shake it (it do not need to hit atom directly for that), this shaking generates heat and this mean also resistance. If there is quantified phonon this shaking is too small to push phonon to next energy level and so electron (current) cannot lose its energy. But something must simultaneously prevent electrons from being accelerated (if atoms cannot get energy from electrons they also cannot decrease electrons speed), or electrons will eventually get enough energy to overcome this phonon barrier.

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