Strain-Coupled Charge-Density Waves in a Linear Conductor

X-ray studies of tetrathiafulvalenium-thiocyanate [TTF${\mathrm{}\left(\mathrm{SCN}\right)\mathrm{}}_{0.588}$] show a Peierls instability with one-dimensional charge-density waves near 300 K followed by three-dimensional order at $T_c=180\mathrm{}$ K. Below $T_c$, 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.