Transport properties of dynamically disordered chains and applications to TTF-TCNQ and related compounds

Abstract

A model for the high-temperature transport properties of one-dimensional conductors with very narrow bands and strong electron-phonon couplings is discussed. It is argued that electronic states can be viewed as effectively localised over some characteristic time scale and that the conductivity is due to dynamic rearrangement of the localisation region. For a series of charge-transfer complexes like tetrathiofulvalene-tetracyanoquinodimethane (TTF-TCNQ) it is argued that a consistent interpretation of the almost identical temperature dependences of the high-temperature conductivities and yet apparently totally dissimilar temperature dependences of the thermopowers is possible if one regards both the donor and the acceptor stacks as conducting. In particular, for TTF-TCNQ where most of the relevant parameters are known, quantitative calculations of the magnitudes and the temperature dependences of the conductivity and the thermopower are presented. The results are in excellent agreement with the observed values.