New Mechanism for a Phonon Anomaly and Lattice Distortion in Quasi One-Dimensional Conductors

It is shown that for sufficiently strong repulsive electron-electron interactions a quasi one-dimensional conductor has a phonon anomaly with wave vector component $4k_{\mathrm{F}}$ and an associated phase transition to a new kind of correlated charge-density wave state and lattice distortion, which can account for recent x-ray experiments on tetrathiafulvalene-tetracyanoquinodimethane. In the ordered state, the charge-density excitations are solitons and there is a gap in their spectrum.