Abstract
The conductivity and the thermoelectric power have been studied experimentally on the organic conductors bis-tetramethyltetraselenafulvalenium hexafluorophosphide [P] and bis-tetramethyltetrathiafulvalenium hexafluorophosphide [P] and their solid solutions: . Dramatic effects are seen in already when dilute concentrations of TMTTF molecules are introduced in the TMTSF chains, and for , shows generally activated behavior. The thermopower, on the contrary, remains basically unaffected for at least as large as 0.25. These unusual findings are attributed to the small transverse transfer integral associated with the TMTTF molecule, which leads to large on-site Coulomb repulsion. The parallel transfer integrals appear to be very similar for the two constituent molecules. A slight dependence of , appearing below approximately 100 K, is attributed to enhanced one-dimensionality when the amount of TMTTF is increased. Close to and below the spin-density-wave ordering temperature, more marked dependences appear, indicative of impurities. The salt behaves generally similar to the pristine TMTTF material, though dominated by additional impurity levels.
- Received 19 August 1983
DOI:https://doi.org/10.1103/PhysRevB.29.842
©1984 American Physical Society