Infrared studies of thin films of TTF-TCNQ are analyzed to obtain the frequency-dependent conductivity. In the metallic state the results indicate an energy gap (0.14 eV) with a collective mode at zero frequency. Below 58 K the conductivity peak moves away from zero frequency into the far infrared.

• Received 4 March 1974

DOI:https://doi.org/10.1103/PhysRevLett.32.1301