Temperature dependence of the transfer integrals in the (TMTSF)₂X and (TMTTF)₂X families

Organic Superconductors: When Correlations and Magnetism Walk in

“…the conduction band is quarter-filled. However, non-uniformity of the intermolecular spacing had been noticed from the early structural studies of (TMTTF) 2 X crystals [62] due to the periodicity of the anion packing twice the periodicity of the molecluar packing. This non-uniformity provides a dimerization of the intrastack overlap which is important in the sulfur series (prominent 1/2 Umklapp scattering) but still present although less developed in some members of the (TMTSF) 2 X series.…”

“…is characterized by an intrachain or longitudinal Fermi energy E F = v F k F which revolves around 3000 K in (TMTSF) 2 X [62,118]; here v F and k F are the longitudinal Fermi velocity and wave vector. This energy is much larger than the interchain hopping integral t ⊥ (≈ 200K), in turn much bigger than the second-nearest neighbor transverse hopping amplitude t ⊥ .…”

One-dimensional electronic properties of the Bechgaard salts

“…The first one comes from X-ray and neutron measurements which have provided accurate values for the structural parameters of these compounds [4]. Using them as inputs, quantum chemistry calculations [5] have provided values for various hopping integrals, in particular for the hopping integrals along the stacks tl and t2, for a few compounds (see table 1). The integrals relative to TMTSF compounds are roughly twice as large as those relative to TMTTF compounds mainly because the selenium 4 p orbitals are more extended than the sulfur 3p ones.…”

One Dimensional Organic Superconductors

“…Consequently, according to the single particle band calculation all compounds in the X (TM) 2 series should be found conducting. On Table 1 we have reported the band parameters of different members of the X (TM) 2 family as they can be computed from the crystallographic data [46]. The sulfur compounds exhibit bands which are significantly narrower and more dimerized than the selenide ones.…”

“…the conduction band is quarter-filled. However, non-uniformity of the molecular packing had been noticed from the early structural studies of X (TMTTF) 2 crystals [46]. There exists a dimerization of the overlap between molecules along the stacks, a situation which is more developed in the sulfur series although it is still encountered in some members of the X (TMTSF) 2 , see Table 1.…”