Incommensurate-commensurate transition in TaS3

Abstract

Careful electron diffraction measurements show that the Peierls distortion, which appears in TaS3 with the orthorhombic structure at To = 215 K, is weakly incommensurate with the underlying lattice. The periodicity of the distortion is temperature dependent and locks at T'0 = 140 K to a value equal to four times the lattice constant. This incommensurate-commensurate transition is observable in transport measurements and also in dynamical properties of the charge density wave. We explain this transition with a model where the charge density waves on two sets of chains are strongly coupled.