Dielectric constant in the incommensurate phase ofRb2ZnCl4

Abstract

The incommensurate-commensurate phase transition in ${\mathrm{Rb}}_2$Zn${\mathrm{Cl}}_4$ is investigated by dielectric measurements. The steep increase of $\epsilon$ and the small difference between the Curie-Weiss and the transition temperature favor the interpretation that the transition is of second order. The Curie-Weiss law is found to be obeyed just above the transition. A Landau-type theory for the linear as well as nonlinear response of a multisoliton lattice is developed which can account very well for $\epsilon \mathrm{}\left(T\right)\mathrm{}$ in the whole incommensurate phase.