Molecular superconductors

The discovery of the first molecular superconductor containing a transition metal complex, TTFJNi (dmit)2]2 (386), initiated a significant effort into the search for more of these fascinating materials.10 9... 

Since the discovery of the first organic semiconductor perylene-bromine complex in 1954 [1], a large number of molecular conductors, including more than 100 molecular superconductors, have been prepared. Conducting molecular materials are characterized by the following features ... 

Scheme 15 Component molecules for molecular superconductors except TMTSF, TMTTF, FT and BO systems. Numbers in bracket are the total members of each superconductor and the highest (in K)...

There are three kinds of superconductors based on acceptor molecules M(dmit)2 (Scheme 15, M = Ni, Pd) [293], picene [294], and Ceo [141-143], Cgo system has the highest Tc for molecular superconductors (Tc = 38 K) followed by the picene one Tc = 18 K) however, those two systems are very unstable chemically (caused partly by very weak electron accepting ability) and decompose immediately at ambient condition. 

Kobayashi A, Kato R, Kobayashi H, Moriyama S, Nishio Y, Kajita K, Sasaki W (1987) Crystal and electronic structures of a new molecular superconductor, K-(BEDT-TTF)2l3. Chem Lett 16 459 62... 

Gritsenko V, Tanaka H, Kobayashi H, Kobayashi A (2001) A new molecular superconductor, K-(BETS)2T1C14 [BETS = bis(ethylenedithio)tetraselenafulvalene]. J Mater Chem 11 2410-2411... 

Molecular superconductors are of more immediate practical interest. Experimental evidence indicates superconductivity is incipient at 30 K, a temperature above the critical temperature for other known materials. Superconductors have a major potential use in providing two distinguishable states associated with tunneling of electron pairs through a... 

Figure 1 Prototype molecules TTF (tetrathiafulvalene and TMTSF (tetramethyl-tetraselenafulvalene) which are used for the elaboration of organic conductors TTF-TCNQ or superconductors (TMTSF)2X. View of the crystal structure of some molecular superconductors (a) (TMTSF)2PF6 (b) (alkali)3 C (c) (BEDT-TTF)2Cu(SCN)2 side view (d) view along the axis perpendicular to the conducting plane.

Table 3 Parameters Describing the Superconducting Phase of Molecular Superconductors...

Several important and recent aspects of the physical properties of these molecular superconductors have been left by the roadside. It is the case, for example, for the physics of quasi-one-dimensional conductors at very high magnetic field when the undistorted phase exhibiting a metal-like behavior at zero field should become localized [152]. Reentrance of a superconducting instability is also expected at very low temperature under... 

I gratefully acknowledge the constructive and fruitful cooperation which has been very active between Orsay and several laboratories in physics and chemistry all over Europe, Quebec, and South Korea. The list of colleagues and co-workers who have been involved in the research on molecular superconductors is so long that I would rather refer the reader to the reference list, where the names of colleagues who should be thanked for their cooperation can easily be found. This research has been supported partially by EEC Esprit Basic Research Action 3121, Stimulation Program CI-CT 90-0863 at DG XII, DRET contract 88/198, and CNRS-GDR Qo-... 

Kobayashi, A., Kato, R., Kobayashi, H., Moriyama, S Nishio, Y, Kajita, K. and Sasaki, W. (1987). Crystal and electronic structure of a new molecular superconductor-(BEDT-TTF)2l3. Chem. Lett., 459-62. [192]... 

The synthesis of macroscopic amounts of C o and C70 (fullerenes) has stimuiated a variety of studies on their chemical and physical properties. We recently demonstrated that C o and C70 become conductive when doped with alkali metals. Here we describe iow-temperature studies of potassium-doped both as films and bulk samples, and demonstrate that this material becomes superconducting, Superconductivity is demonstrated by microwave, resistivity and Melssner-effect measurements. Both polycrystalline powders and thin-flim samples were studied. A thin film showed a resistance transition with an onset temperature of 16 K and essentially zero resistance near 5 K. Bulk samples showed a well-defined Meissner effect and magnetic-field-dependent microwave absorption beginning at 18 K. The onset of superconductivity at 18 K is the highest yet observed for a molecular superconductor. 

The universally accepted tests for superconductivity, namely a transition to zero resistance and a Meissner effect showing the expulsion of magnetic field, demonstrate unequivocally the existence of superconductivity in K Cso. The 18-K transition temperature is the highest yet reported for a molecular superconductor. This may be compared with the previously reported occurrence of superconductivity at 0.55 K in potassium-intercalated graphite. We expect that optimization of composition and crystallinity will lead to further improvement in the superconducting properties. ... 

---