| Popis: |
The x-ray crystal structure of the bromide salt of tetrathiafulvalene (TTF)-${\mathrm{Br}}_{0.79}$ shows incommensurate cation and anion sublattices, with a static modulation of each stack at the periodicity of the opposing stack. If the on-site Coulomb interactions were very small compared with the bandwidth, this modulation would induce an energy gap at twice the Fermi wave vector and hence a commensurate Peierls transition would be possible. If the Coulomb interactions were very large, (TTF)-${\mathrm{Br}}_{x}$ would be a room-temperature semiconductor. Transport, magnetic, thermal, and optical measurements are presented, which indicate that the Coulomb interactions are not very large compared with the bandwidth, estimated at $4t\ensuremath{\sim}1.1$ eV. Hence, the system can be viewed as undergoing a commensurate Peierls transition at \ensuremath{\sim} 170 K. |
