The ubiquity of the new organic conductor ditetramethyldithiadiselenafulvalene-hexafluorophosphate (TMDTDSF )2PF6

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Abstract
Preparation, magnetic and transport properties under pressure of an organic conductor based on the new molecule di-tetramethyldithiadiselenafulvalene (TMDTDSF )2PF6 are reported. This compound is isostructural to the (TMTTF-TMTSF )2X series. At ambient pressure, Coulomb induced localization is observed below 180 K. Spin-Peierls ordering occurs at 20 K and a spin density wave state is stabilized below 7 K. The onset of an antiferromagnetic state has been conclusively established by the vanishing of the ESR spectrum at the Zeeman frequency (X-band) and the concomitant occurrence of a new resonance line at a resonance field (Hr ~ 5 kOe) far above the Zeeman field (g = 2) and whose angular dependence provides the signature for antiferromagnetic resonance. Both charge localization and spin-Peierls states are suppressed under pressure. Above 20 kbar, in spite of the stabilization of the conducting state (metallic-like) at low temperatures no superconductivity can be observed down to 0.56 K. This feature could be related to the existence of structural disorder or to the weakness of the interchain coupling in the title compound. (TMDTDSF)2PF6 can be considered as a prototype material for the study of the instabilities occurring in a quasi 1-D electron gas at low temperatures via an adequate adjustment of the pressure