We study the consequences of the previously overlooked fact that in most quasi-one-dimensional materials with a Peierls-Fröhlich ground state the lattice zero-point motion is comparable to the lattice distortion. The density of states deviates significantly from that of a rigid lattice, containing a tail of strongly localized states below the gap. Moreover, thermal lattice motion causes the tail to increase significantly with temperature. This is consistent with the subgap optical absorption seen in these materials.

• Received 2 March 1992

DOI:https://doi.org/10.1103/PhysRevLett.69.1085