Improved measurement of the far-infrared optical properties of semiconducting tetrahiafulvalene tetracyanoquinodimethane

Improved far-infrared reflectivity data are presented of tetrathiafulvalene tetracyanoquinodimethane in its insulating phase, for radiation polarized withE∥b. The conductivity spectrum obtained shows a pinned charge-density wave at 35 ${\mathrm{cm}}^{-1\mathrm{}}$, less intense than that obtained previously, and an asymmetric peak at the energy gap of 300 ${\mathrm{cm}}^{-1\mathrm{}}$ in good agreement with that predicted theoretically. The agreement with powder spectra is also improved.