Strain-coupled charge-density waves in a linear conductor

X-ray studies of tetrathiafulvalenium-thiocyanate [TTF(SCN)0.588] show a Peierls instability with one-dimensional charge-density waves near 300 K followed by three-dimensional order at Tc=180 K. Below Tc, an interchain competition between both elastic forces and Coulomb interactions drives a temperature-dependent monoclinic strain. A Landau theory including both charge-density and strain order parameters describes the relative TTF chain slip and the superlattice phase variation.