Bechgaard organic 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... 

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... 

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. 

Attempts have also been made to design one-dimensional organic superconductors based on donor-acceptor interaction (Bechgaard Jerome, 1982). For this purpose it... 

At birth, the molecular metal was the one-dimensional metal. KCP and TTF-TCNQ are typical examples. The one-dimensional metal, however, is not a metal in the low temperature region due to the instability of the planar Fermi surface. Of course, this instability has provided rich physics [3], but is not favorable to the superconductivity. Therefore, chemists made efforts to increase the dimensionality of the electronic structure by the chemical modification with great success. The first organic superconducting system, the Bechgaard salt, is a quasi-one-dimensional system [4]. BEDT-TTF salts, the second-generation organic superconductors, have typical two-dimensional Fermi surfaces [5]. Three-dimensional Fermi surface has been found in the DCNQI-Cu salt [6]. 

TMTSFljX or Bechgaard Salts the First Organic Superconductors... 

By using the donor TMTSF (tetramethyltetraselenafulvalene, 11b) and the newly developed technique of electrocrystallization, the groups of Bechgaard and Jerome found in 1990 the first organic superconductor, (TMTSF)2PF5, with Tj = 0.9 K at an applied pressure of 10 kbar [29]. Here the lateral two-dimensional Se-Se interactions and the applied pressure together defeat the Peierls transition. The first ambient-pressure superconductor, (TMTSF)2C104, followed quickly Fig. 4 shows its crystal structure. 

Fig. 10.2 The crystal structure of the Bechgaard salt (TMTSF)2PF6, the first organic superconductor. The H atoms are - as usual -left off for clarity. The PFg anions are arranged between the stacks of the organic molecules. The perpendicular spacing within the stacks...

Bechgaard-Jerome group finds first organic superconductor (TMTSeF)2PFg [34]... 

To be useful in ET, the DNA bases should be substituted with simpler orgauic moles of the type involved in the superconducting Bechgaard salts (Eigure 18.24). PFg molecules, which are easily reduced, should be used to create positive carriers in the same way as in the case of organic superconductors. 

A. Contraction of lattice members in the wake of a passing electron. B. Attraction of a second electron to the lattice contraction of the first electron. C. Oscillation of the two electrons in the Cooper pair in response to vibrations of the lattice members. Figure adopted from Bechgaard, B., and Jerome, D. "Organic Superconductors." Set. Am., 247,52-61 (1982). 

Takahashi, T., Jerome, D., and Bechgaard, K., Observation of a magnetic state in the organic superconductor (TMTSE)2C104, J. Phys. (Paris) Lett., 43, L565, 1982. 

In the 1960s, a completely new form of organic conductors was found. Structurally, these new conductors turned out to be one-dimensional stacks of planar molecules. The conductivity is in the direction perpendicular to the tt-system. In the 1980s, Klaus Bechgaard, and Denis Jerome discovered organic, one-dimensional superconductors. 

Bechgaard later used the even stronger electron acceptor molecule, perchlorate (CIO4), instead of PFg". He obtained a superconductor below Tc = 1.4 K at ambient pressure. All these organic conductors show magnetic ordering above the critical temperature up to several tens of kelvin, the transition temperature. 

Jensen was an efficient transmitter of the tradition of sulfur chemistry in Denmark, and several young scientists were inspired by him. For example, Bechgaard became a leading figure in the successful search for organic metals and superconductors ("Bechgaa salts") via his deep insight into sulto and selenium chemistry. 

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