Source of the metallic conductivity in tetrathiafulvalene- tetracyanoquinodimethane (TTF-TCNQ)

The optical-conductivity data have been reinterpreted and shown to have the same form as the dc conductivity in the region above the transition temperature. The apparent energy gap at 1000 cm-1 seems to have little influence on the conduction electrons since there is no difference between the conductivity on either side of the gap. From the absence of any linear temperature dependence, the maximum electron-phonon coupling constant is estimated at 0.2. Analysis of the conductivity in terms of the electron-electron interaction provides a plausible description of data. © 1976 The American Physical Society.