Modulated Structures Associated with Charge-Density Waves

We report on the occurrence of periodic lattice distortions associated with charge-density waves in low-dimensional metallic structures. After presenting a brief theoretical background concerning the conditions under which such distortions may occur, we consider a few examples of low-dimensional conductors that undergo such periodic distortions. In particular, we discuss transition-metal dichalcogenides and oxide bronzes. Emphasis is placed on showing how the transition to a charge-density-wave state may be followed not only by structural studies, but also by studies of some of the electronic properties of these compounds, particularly their transport properties. (Author)