Electronic properties of TTF-TCNQ : a connection between theory and experiment

Reinterpretation of the experimentally determined imaginary part of the spin excitation response at q = 2 kF has led to the existence of a maximum in constant volume temperature dependences. This fact, together with the observed similarity between ρ/T and Im χ(2 kF), has triggered the development of a theory based on existing treatments for the intra-chain electron-electron interactions modified by phonon pseudo-gap effects. Parameters for electron-electron and electron-phonon couplings have been derived from a fit with the data of Im χ(2 kF) and the static susceptibility at selected pressures and temperatures. This study shows the importance of both electron-electron and electron-phonon interactions in the electronic properties of TTF-TCNQ. Moreover, it reconciles the large magnetic enhancement with the structural phase transition properties.