A new survey of the physical properties of the (TMTTF)2 X series. Role of the counterion ordering

Slowing down of the relaxational dynamics at the ferroelectric phase transition in one-dimensional (TMTTF)2AsF6

“…They are formed of stacks of the organic molecules tetramethyltetrathiofulvalene (TM=TMTTF) [1] or tetramethyltetraselenafulvalene (TM=TMTSF) [2] with X=PF 6 , AsF 6 , SbF 6 , Br, SCN, ClO 4 , ReO 4 , etc. as counterions, which occupy loose cavities formed by the methyl groups of the organic molecules.…”

“…Low dimensional electronic systems, of which the organic charge transfer salts (TM) 2 X [1,2] are paramount examples, serve as model systems for the investigation of strong correlations. They are formed of stacks of the organic molecules tetramethyltetrathiofulvalene (TM=TMTTF) [1] or tetramethyltetraselenafulvalene (TM=TMTSF) [2] with X=PF 6 , AsF 6 , SbF 6 , Br, SCN, ClO 4 , ReO 4 , etc.…”

Charge, spin, and lattice effects in the spin-Peierls ground state of MEM(TCNQ)2

“…In the (TMTTF) 2 PF 6 compound for instance, the transition takes place at T SP ≈ 18 K at ambient pressure for the salt with hydrogenated TMTTF molecule [10][11][12] and at 13 K in the deuterated one [13]. These quasi-1D materials, however, display a slightly dimerized structure leading to a Mott insulating gap below T ρ ≈ 230K [14], followed by a charge ordered superstructure (CO) at T CO ≈ 65K [15,16](T CO ≈ 84K in deuterated [17,18]) whose proximity with the SP transition has prevented the full characterization of its order parameter. Indeed, inhomogeneous dielectric [18] and elastic [19] behaviors were observed in the vicinity of the SP transition for the hydrogenated and deuterated PF 6 salts.…”

Basic considerations on broken-symmetry states of organic superconductors

“…At low pressure, the nature of the transition in (TMTTF) 2 X shows qualitative differences with respect to the Bechgaard salts: antiferromagnetism is stabilized from a paramagnetic state that is insulating. The metal to insulator 'transition' occurs at a characteristic temperature usually denoted as T ρ ∼ 10 2 K (Figure 1), below which electrical transport develops a thermally activated behavior [18]. Since spin degrees of freedom remain unaffected at T ρ − as shown by the absence of anomaly in the spin susceptibility at that temperature [6] − (TMTTF) 2 X are good examples of Mott insulators below T ρ [19].…”