Superconductors organic

However, when pressure was applied to these metallic organic systems, the phenomenon of superconductivity was detected. The 

Metallic conduction has recently been observed in specially-prepared organic compounds, such as polyacetylene, polypyrrole, and polyaniline, having conductivities of the order 10 9 (ohm-cm)1 but by proper doping these conductivities can be increased to 102 (ohm-cm)-1. Some of the organic metallic systems have also been converted into the superconducting state by proper doping, but in all cases the Tc remains at very low temperature. 

Several chapters, reviews, and a recent book have been published on these materials, and the area is rapidly growing, becoming known as the Organic Solid State . This supplementary reading is presented as references 34-42. 

Few oxide superconductors were known prior to 1985 and we shall now return to these so that we can discuss these materials in reference to their crystal structure classes. There are only three broad structural categories in which most of the oxide superconductors occur. The important structural types include sodium chloride (rocksalt, or Bl-type), perovskite (E2X), and spinel (Hlx). 

Superconductivity is now known in about 40 charge-transfer (CT) salts, the majority of which are derived from bis-(ethylene dithio)-tetrathiafulvalene (ET). The current record of highest of 12.8 K is held by (ET)2Cu[N(CN)2]Cl (Williams et ai, 1991). In 

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According to the BCS theory, in superconductivity there is a relation between the energy gap A and the critical temperature, 2A(0) = 3.52 Tc (in the case of weak electron-phonon coupling). A(0) is the value of the energy gap at T = 0 K. 

These hopes have, to be sure, not been fulfilled. Instead of an excitonic superconductor, motivated by the suggestion of Little, experimentalists have since found a large number of organic superconductors with conventional, or in any case not excitonic coupling mechanisms. 

The organic superconductors can be divided into three classes  

Readers who wish to study the organic superconductors in detail are especially referred to the book by Ishiguro et al. [Ml]. Other important reviews can be found in [M2] and [3]. 

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Superconductivity has also been discovered in rather exotic materials, including the following Buckminsterfullerene (Cgo) doped with ICI Carbon nanotubes (superconductivity in just one direction) Nickel borocarbides, which contain Ni2 B2 layers alternating with R C sheets, where R is a rare earth element such as Er and organic superconductors that contain planar organic cations and oxoanions. Chemists and physicists continue to study these and other families of superconductors. 

Exactly this approach led to the discovery of the first organic superconductors, the Bechgaard CT salts of tetramethyltetraselenafulvalene (TMTSF, 3) with various counteranions (TMTSF)2PF6 (under pressure) in 1980120 and... 

J.M. Williams, J.R. Ferrero, R.J. Thorn, K.D. Carlson, U. Geiser, H.H. Wang, A.M. Kini and M.-H. Wangbo, Organic Superconductors (Including Fuller enes), Prentice-Hall, Englewood Cliffs, NJ, 1992. 

Keywords Cation-radical salts, Molecular conductors, Organic superconductors, Organometallic anions, Tetrakis(trifluoromethyl)metallates, Tetrathiafulvalene... 

Williams JM, Ferraro JR, Thom RJ, Carlson KD, Geiser U, Wang HH, Kini AM, Whangbo MH (1992) Organic superconductors (including fullerenes). Prentice Hall, Englewood Cliffs, New Jersey... 

Ishiguro T, Yamaji K, Saito G (1998) Organic superconductors, vol 88, 2nd edn. Springer, Berlin Heidelberg New York... 

The first organic superconductor (Bechgard and Jerome, 1980) with a critical temperature Tc- 0.9 K other organic superconductors later reached Tc 13 K. 

Ishiguro, T. Yamaji, K. Saito, G. (1998) Organic Superconductors, Springer-Verlag, Berlin. 

TMTSF)2C104 exhibits Tc - 1 -4 K at P = 0 GPa, hence becoming the hrst organic superconductor at ambient pressure (Bechgaard etal, 1981). The tetrahedral... 

Table 1.8. Material, P and of selected molecular organic superconductors classified according to the point group of the donor...

The neutral insulator TMTSF, which shows field-effect conduction with /Th — 0.2 cm s (Nam et al, 2003), when transformed into a Bechgaard salt also becomes superconducting, but at lower temperatures. In this case the perfect segregation of organic and inorganic molecular planes leads to confined electronic systems, which in the normal state are quasi ID. Organic superconductors based on the BEDT-TTF molecule represent the case of pure 2D electronic systems. 

Elastic-inelastic collision model, Szilard-Chalmers reaction and, 1 269 Electrical conduction, in organic superconductors, 29 278-286 Electrical conductivity of chalcogenide halide compounds, 23 331 of Group IB, 23 337-339, 342, 346-349 photoelectric effects, 23 368, 410 semiconductors, 23 368, 390, 395-396, 400-402, 410-412 superconductors, 23 375-377 of graphite intercalation compounds, 23 290, 294, 309-310, 312, 317-318 Electric discharges arc type, 6 146-147 chemical reactions in, 6 189-191 chemical reactions in, 6 143-206... 

Magnetie susceptibility, 46 383-384 organic superconductors, 29 286-290 spin-equilibrium complexes, 32 4-6 temperature dependence, 41 310 Magnetism, 43 180-181, see also Heterobime-tallics... 

Keywords Charge transfer solid Electronic dimensionality Functional organic solid Ionicity diagram Organic metal Organic superconductor Phase transition Quantum spin liquid state Switching... 

Metallic Doped Polymers and Unidentified Organic Superconductors. 101... 

There are several comprehensive textbooks and review articles devoted to organic superconductors [3,4,182-186] which describe design and preparation, crystal and band structures, chemical, transport, magnetic, optical, and thermal properties, and theory. 

These experimental facts indicate that this system can be an excellent model of band-filling control, and will be a good candidate for making a superlattice composed of Mott insulator/superconductor hetero-junctions. It should be emphasized that their lattice parameters are nearly kept constant through such an anion modification, which is the most essential feature for achieving the successful tuning of Tc in an organic superconductor. 

Kahlich S, Schweitzer D, Heinen I, Lan SE, Nuber B, Keller HJ, Winzer K, Heiberg FIW (1991) (BED0-TTF)2Re04 (H20) a new organic superconductor. Solid State Commun... 

Mori H (2006) Materials viewpoint of organic superconductors. J Phys Soc Jpn 75 051003/1-15... 

Jerome D (1991) The physics of organic superconductors. Science 252 1509-1514. A more detailed diagram was then proposed Dumm M, Loidl A, Travel BW, Starkey KP, Montgomery LK, Dressel M (2000) Electron spin resonance studies on the organic linear-chain compounds (TMTCF)2X (C = S, Se X = PFg, AsFg, CIO4, Br). Phys Rev B61 511-521... 

Urayama H, Yamochi H, Saito G, Nozawa K, Sugano T, Kinoshita M, Sato S, Oshima K, Kawamoto A, Tanaka J (1988) A new ambient pressure organic superconductor based on BEDT-TTF with higher than 10 K (T = 10.4 K). Chem Lett 17 55-58... 

Komatsu T, Nakamura T, Matsukawa N, Yamochi H, Saito G (1991) New ambient pressure organic superconductors based on BEDT-TTF, Cu, N(CN)2 and CN with = 10.7 and 3.8 K. Solid State Commun 80 843-847... 

Komatsu T, Matsukawa N, Nakamura T, Yamochi H, Saito G (1992) Isotope effect on physical properties of BEDT-TTF based organic superconductors. Phosphorus Sulfur Silicon Relat Elem 67 295-300... 

Ishiguro T, Ito H, Yamauchi Y, Ohmichi E, Kubota M, Yamochi H, Saito G, Kartsovnik MV, Tanatar MA, Sushko YV, Logvenov GY (1997) Electronic phase diagrams and Fermi surfaces of k-(ET)2X, the high T organic superconductors. Synth Met 85 1471-1478... 

Ito H, Watanabe M, Nogami Y, Ishiguro T, Komatsu T, Saito G, Hosoito N (1991) Magnetic determination of Ginzburg-Landau coherence length for organic superconductor /c-(BEDT-TTF)2X (X = Cu(NCS)2, Cu[N(CN)2]Br) effect of isotope substitution. J Phys Soc Jpn 60 ... 

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