New Organic Superconductors β-(BDA-TTP) 2 X [BDA-TTP = 2,5-Bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene; X - = SbF 6 - , AsF 6 - , and PF 6 - ] (original) (raw)
Related papers
Physica C: Superconductivity, 1996
We report the first study of the effect of isotopic substitution on the superconducting transition temperature in the K-(ET)2M(CF3)4(l,l,2-trihaloethane) [ET-bis(ethylenedithio)tetrathiafulvalene; M= Cu, Ag, and Au] family of organic superconductors, where M(CF3) 4-is a large, discrete (non-polymeric) anion. This work also represents the first single crystal determinations of T¢ in this series of superconductors. Substitution of the eight hydrogen atoms of the ET electron-donor molecule by deuterium causes the T¢ of KL-(ET)2Ag(CF3)4(1-bromo-l,2-dichloroethane) to increase from 2.90 + 0.04 K to 3.11 + 0.04 K (here K L signifies a phase with a lower T c, between 2 and 6 K, and K H is a different phase with higher To, between 9 and 12 K). Thus, this is the first example which demonstrates that the inverse isotope effect previously observed in K-(ET)2Cu(SCN) 2 (this salt contains a "self-assembled" polymeric anion and was the first organic superconductor with T¢ > 10 K) is also present in a K-phase ET-based superconductor containing a discrete anion. This finding is significant for the future development of organic superconductors with novel physical properties, because entirely new directions for the synthesis of unique superconducting systems are now possible with the use of large discrete anions which can be synthesized in a rational and repeatable fashion (as opposed to randomly synthesized self-assembled polymeric anions).
Physica C, 1996
We report the first study of the effect of isotopic substitution on the superconducting transition temperature in the kappa-(ET) 2M(CF 3) 4(1,1,2-trihaloethane) [ET = bis(ethylenedithio)tetrathiafulvalene; M = Cu, Ag, and Au] family of organic superconductors, where M(CF 3) 4- is a large, discrete (non-polymeric) anion. This work also represents the first single crystal determinations of Tc in this series of superconductors. Substitution of the eight hydrogen atoms of the ET electron-donor molecule by deuterium causes the Tc of kappaL-(ET) 2Ag(CF 3) 4(1-bromo-1,2-dichloroethane) to increase from 2.90 ± 0.04 K to 3.11 ± 0.04 K (here kappaL signifies a phase with a lower Tc, between 2 and 6 K, and kappaH is a different phase with higher Tc, between 9 and 12 K). Thus, this is the first example which demonstrates that the inverse isotope effect previously observed in kappa-(ET) 2Cu(SCN) 2 (this salt contains a ``self-assembled'' polymeric anion and was the first organic superconductor with Tc>10 K) is also present in a kappa-phase ET-based superconductor containing a discrete anion. This finding is significant for the future development of organic superconductors with novel physical properties, because entirely new directions for the synthesis of unique superconducting systems are now possible with the used of large discrete anions which can be synthesized in a rational and repeatable fashion (as opposed to randomly synthesized self-assembled polymeric anions).
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2010
RHF and DFT calculations were carried out to study the optimized molecular geometries and vibrational characteristics of the 4,5-ethylenedithio-1,3-dithiole-2-thione (EDT-DTT) and 4,5-ethylenedithio-1,3dithiole-2-one (EDT-DTO) molecules and their radical cations and anions. It is found that the anionic radical of the EDT-DTO molecule is unstable. Both the neutral molecules and their radical cations have non-planar structures with C 2 symmetry while the radical anion of the EDT-DTT molecule has nonplanar structure with C 1 symmetry. It is found that the most of the vibrational characteristics of the radicals are similar to their corresponding neutral molecules, however, for some of the modes significant changes are noticed. As a result of anionic radicalization of EDT-DTT, the IR intensity and Raman activity increase and Raman band becomes polarized for both the CH 2 twisting modes. Drastic enhancements in the Raman activity and reduced IR intensity are noticed for the C S/O stretching mode in going from neutral molecules to their radical ions consistent with charge separation along this bond. The C S and C C stretching wavenumber changes are consistent with corresponding bond length changes in going from neutral to their radical ions.
Contrasted structural properties of organic superconductors
Synthetic Metals, 1987
We present structural studies of organic conductors and superconductors of the (TMTSF)2X and (BEDT-TTF)2X families. These materials undergo a large variety of structural phase transitions like ordering of non-centrosymmetric anions Xin the (TMTSF)2X salts and commensurate ((BEDT-TTF)2Re04) or incommensurate (8(BEDT-TTF)213, (TMTSF)2SCN) lattice modulations. We shall pay special attention on new results concerning the pressure induced anion-ordering transformation in (TMTSF)2ReO 4 and the two competing phase transitions of (TMTSF)2PF202.
Some electronic properties of the organic superconductor β - (BEDT-TTF )2I3
Journal de Physique, 1989
2014 Nous avons mesuré de 300 K à 4,2 K la magnétorésistance, la susceptibilité et l'anisotropie magnétique de monocristaux du supraconducteur organique bi-dimensionnel 03B2L-(BEDT-TTF)2I3. A partir de la magnétorésistance suivant c*, nous avons calculé une valeur de 0,5 meV pour l'intégrale de transfert tc dans un modèle de liaisons fortes. De plus, ces mesures indiquent que l'anisotropie de conductivité dans le plan a-b à basse température est d'un facteur cinq. La faible valeur du temps de relaxation (0,5 ps à 9 K) indique que le transport électronique entre plans devient incohérent, ce qui peut affecter la température de transition supraconductrice. La densité d'états dérivée de la susceptibilité de spin est en bon accord avec celle obtenue par chaleur spécifique. Lorsque le champ magnétique est dirigé perpendiculairement aux plans conducteurs, l'anisotropie magnétique provient en partie d'un diamagnétisme des électrons de conduction qui varie avec la température.
New Journal of Physics, 2012
We perform a first principles band calculation for a group of quasi-twodimensional organic conductors β-(BDA-TTP) 2 M F 6 (M =P, As, Sb, Ta). The ab-initio calculation shows that the density of states (DOS) is correlated with the band width of singly occupied (highest) molecular orbital (SOMO), while it is not necessarily correlated with the unit cell volume. The direction of the major axis of the cross section of the Fermi surface lies in the Γ-B direction, which differs from that obtained by the extended Hückel calculation. Then, we construct a tight-binding model which accurately reproduces the ab-initio band structure. The obtained transfer energies give smaller dimerization than in the extended Hückel band. As for the difference of the anisotropy of the Fermi surface, the transfer energies along the inter-stacking direction are smaller than those obtained in the extended Hückel calculation. Assuming spinfluctuation-mediated superconductivity, we apply random phase approximation (RPA) to a two-band Hubbard model. This two-band Hubbard model is composed of the tight-binding model derived from the first principles band structure and an on-site (intra-molecule) repulsive interaction taken as a variable parameter. The obtained superconducting gap changes sign four times along the Fermi surface like in a dwave gap, and the nodal direction is different from that obtained in the extended Hückel model. Anion dependence of T c is qualitatively consistent with the experimental observation.
Some electronic properties of the organic superconductor &# 946;-(BEDT-TTF) 2I3
2011
2014 Nous avons mesuré de 300 K à 4,2 K la magnétorésistance, la susceptibilité et l'anisotropie magnétique de monocristaux du supraconducteur organique bi-dimensionnel 03B2L-(BEDT-TTF)2I3. A partir de la magnétorésistance suivant c*, nous avons calculé une valeur de 0,5 meV pour l'intégrale de transfert tc dans un modèle de liaisons fortes. De plus, ces mesures indiquent que l'anisotropie de conductivité dans le plan a-b à basse température est d'un facteur cinq. La faible valeur du temps de relaxation (0,5 ps à 9 K) indique que le transport électronique entre plans devient incohérent, ce qui peut affecter la température de transition supraconductrice. La densité d'états dérivée de la susceptibilité de spin est en bon accord avec celle obtenue par chaleur spécifique. Lorsque le champ magnétique est dirigé perpendiculairement aux plans conducteurs, l'anisotropie magnétique provient en partie d'un diamagnétisme des électrons de conduction qui varie avec la température.
Synthetic Metals, 1997
A new approach to the synthesis of organic superconductors has recently been pioneered which involves the use of large, discrete, molecular anions as the charge-compensating entities in these charge transfer salts. The organic electron-donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) has been electrocrystallized with the novel organometallic M(CF 3 ) 4~ (M = Cu, Ag, and Au) anions in a variety of 1,1,2-trihaloethane solvents. Over twenty organic superconductors have been synthesized which can be described by the general formula (ET)2Af(CF 3 ) 4 (l,l,2-trihaloethane). These solvated salts are shown to have highly anisotropic physical properties which can be tuned via modifications of each of their three molecular components: ET electron donor molecule, M(CF 3 ) 4ã nion, and neutral 1,1,2-trihaloethane solvent molecule. Superconductivity has also been observed in an ET salt containing the discrete SF5CH 2 CF2SO 3~ anion with an onset temperature near 5.2 K.