Thiourea in an electric field: Birefringence measurements and the Landau-Ginzburg theory

Abstract
We report birefringence measurements of the field-induced commensurate phase in deuterated thiourea in the whole modulated phase part of the (E,T) plane at atmospheric pressure. A simple Landau-Ginzburg approach is shown to account, in a qualitative and semiquantitative way, for the experimental observation.