Posted on 03/04/2010 6:44:19 PM PST by neverdem
Researchers in Japan have created the first superconducting material based on a molecule of carbon and hydrogen atoms. Although the superconducting transition occurs at a chilly 18K, the simplicity of the molecule, which consists of just five benzene rings, suggests that it will open the door to other molecules that have higher transition temperatures.
Superconductivity occurs when a material is cooled below a certain transition temperature (Tc) so that its electrical resistance disappears. The first superconductors were pure metals and had Tc values close to absolute zero, but over the past 25 years scientists have begun to discover various 'high-Tc' materials, including cuprates and, most recently, iron arsenides. Ideally, the material would have a Tc at or above room temperature, so that it could be used without cooling in technologies such as lossless power transmission and magnetic levitation.
Since the early 1990s scientists have been working on organic superconductors in which conductivity arises in the pi-electrons of unsaturated bonds. But the charge-carrying electrons in these molecules have typically been derived from sulfur or selenium atoms, rather than carbon atoms. Now, however, Yoshihiro Kubozono and colleagues at Okayama University and other Japanese institutions have created the first organic superconductor based on a simple aromatic molecule, picene (C22H14), doped with an alkali metal.
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Picene; right: doped with potassium
© Nature
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The researchers make the superconductor by passing potassium vapour over solid picene, which absorbs the potassium atoms into its lattice. The potassium atoms donate electrons to unoccupied pi-electronic states in the picene molecules, thereby providing the necessary charge carriers for superconductivity. Depending on the potassium content, the material's Tc varies from 7 to 18K.
'Certainly it is an extremely important discovery and one which I think will raise huge interest,' says Neal Skipper, a condensed-matter researcher at University College London, UK. 'There are many other candidate aromatic molecules that may need to be revisited - perhaps Tc can be pushed up even further.' Skipper adds that the mechanism for superconductivity could relate more to doped 3D carbon 'fullerides' than doped graphite, which actually shares a similar herringbone structure.
The Japanese researchers are now studying the effect of different metal atoms in picene, and of metals in other aromatic hydrocarbons. 'The key to making a higher Tc organic superconductor may be an increase in the density of states on the Fermi level,' explains Kubozono. 'In other words, it may be important to use more expanded aromatic hydrocarbons that consist of more than five benzene rings.'
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Although the superconducting transition occurs at a chilly 18K, the simplicity of the molecule, which consists of just five benzene rings, suggests that it will open the door to other molecules that have higher transition temperatures.If experience is any guide, it won't prove to be significantly higher temps.
Think what this superconductivity and a large Tesla Coil could do!
Improve your mind -- employ Laphroiag. *\;-)
If they can get it to the temp of liquid nitrogen, it supports a resonable current density and it is ductile, it will be worth a fortune.
Currently machines that require superconductors (MRI units) require liquid helium, an expensive and recently scarce comodity.
A superconducting ceramic powder of Bi/Sr/Ca/Cu/O system are formed in a film and the c-axes are uniformly aligned with the normal of the film. The alignment of the axes is accomplished by dripping Jack Daniels containing the ceramic powder into ethyl alcohol contained in a reservoir. The ceramic powder is settled on a substrate arranged in the reservoir in film form. After removing ethylalcohol, the ceramic film is fired.
Down in MotownA gritty section of Detroit surrounds one of the city's oldest electric power stations. But the technology that Detroit Edison is installing at the Frisbie substation is pure 21st century -- underground superconducting cables that can transmit immense currents of electricity with near perfect efficiency.
by Peter Fairley
July/August 2001
While increasing energy demands are putting more and more stress on the nation's long-distance power transmission network, cities are suffering their own version of electric gridlock; in many locations, underground transmission lines are fast reaching capacity and are literally burning up. Superconducting cables, like the ones being installed in Detroit, could safely triple the power moving through existing conduits, avoiding the need to dig up the streets -- even making room for fiber-optic communications lines.
The Frisbie demonstration marks a milestone in electricity know-how -- one of the first commercial applications of high-temperature superconductors. These ceramics, first fashioned by IBM researchers in 1986, now transmit alternating currents with nearly zero resistance at temperatures as high as -139 °C (the materials can be cheaply cooled to that temperature using liquid nitrogen). In contrast, conventional copper cables dissipate as much as 10 percent of the power they carry because of resistance; that lost power escapes as heat, which limits just how much juice can flow before the cable melts.
Thanks for the ping. I think cSinha has the best theory of superconductivity.
High Temperature Superconductivity In $Pd-[H(D)]_X$ System (2005)
Sinha, KP
Abstract
High Temperature Superconductivity D System Sinha Department Physics Indian Institute Science Bangalore Sterling Residence Dollar colony Bangalore mail kpsinha gmail com Abstract theoretical model involving phonon and lochon local charged boson mediated pairing electrons D suggested explain the possible observation superconductivity the range when exceeds unity the combined mechanism the lochons have transient existence resulting species The coupling parameter for lochon induced processes depend linearly The model explains the observation the enhancement for varying from While the experimental observations are great importance desirable that other experimental groups confirm the results Keywords Local Charged Bosons x system HTSC Introduction Palladium hydride has been known superconductor from but the low temperature regime with the critical ranging from for the ratio varying from Palladium loaded with hydrogen its isotope deuterium diffusion from gas electrolytic means enter interstitial sites the host lattice leading expansion lattice structure Increased loading produces displacement host metal atoms resulting vacant host sites This renders the deformed host lattice very mobile for which shed their electrons the shell which has positive holes with the same number electrons the band one takes into account that the lattice there are twelve interstitial sites taking both octahedral and tetrahedral which can occupied the value can boosted This ideal situation motivated some wo
Publication details
Download http://eprints.iisc.ernet.in/archive/00005519/
http://eprints.iisc.ernet.in/archive/00005519/01/High_Temperature.pdf
Repository ePrints@iisc (India)
Keywords Physics
Type Preprint
The Fermion-Lochon model and the pseudogap in cuprate superconductors
Sinha, KP (1999) The Fermion-Lochon model and the pseudogap in cuprate superconductors. In: 1999 University of Miami Conference on High Temperature Superconductivity, 7-13 Jan. 1999, Coral Gables, FL, USA, pp. 122-125.
Full text not available from this repository.
Abstract
The interaction mechanism involving fermions and lochons (local charged bosons) located at polarizable dielectric regions in the layered cuprate systems is discussed in the context of the pairing symmetry, the appearance of the resonance peak and the pseudogap which is seen above . It is found that the mechanism allows both s and d waves and the dominance of one or the other depends on the relative values of the Fermi energy and the nearest neighbor hopping integral. The model accounts for the pseudogap and the resonance peak is identified with the local pair fluctuation state. The mechanism, along with a weak phonon contribution, emerges as an acceptable model for NTSC
Item Type: Conference Paper
Additional Information: Copyright of this article belongs to AIP- American Institute of Physics
Keywords: dielectric polarisation;Fermi level;fermions;high temperature superconductors;phonons;resonance
Department/Centre: Division of Physical & Mathematical Sciences > Physics
ID Code: 10297
Deposited By: Srinivas B
Deposited On: 26 Jul 2007
Last Modified: 27 Aug 2008 18:13
Lochon-induced Interlayer Pairing and Gap Anisotropy in Cuprate Superconductors
Sinha, KP and Vytheeswaran, AS (1996) Lochon-induced Interlayer Pairing and Gap Anisotropy in Cuprate Superconductors. In: Solid State Communications, 99 (11). pp. 845-848.
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Abstract
The mechanism involving phonons and lochons (local charged bosons, local pairs) developed earlier for cuprate superconductors is applied for the study of the gap anisotropy in these systems. It is found that besides intraplanar pairing the lochon-induced interlayer pairing gives rise to an anisotropic s-wave gap which is capable of changing sign in some regions on the Fermi surface.
Item Type: Journal Article
Additional Information: Copyright of this article belongs to Elsevier.
Related URLs: http://dx.doi.org/10.1016/0038-1098(96)0...
http://www.sciencedirect.com/science?_ob...
Department/Centre: Division of Physical & Mathematical Sciences > Physics
ID Code: 9307
Deposited By: Sumana K
Deposited On: 17 Jan 2007
Last Modified: 27 Aug 2008 18:01
Why does a low temperature make any difference? The answer is important. If the answer is that the cold slows the physical movement of electrons, we need to know. If the answer is that the cold reduces molecular bond vibrations, we need to know.
Ceramic superconductors have improved tremendously.
I remember when they thought room temp super conduction was within reach. The other holy grail is a ductile SC. To reach full potential, you need a material that can be drawn into wire.
Maybe a metglas manufacturing approach would work, using known (or currently unknown) materials.
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