The coupling between an electric field and mechanical stress in the incommensurate phase

The coupling between an electric field and mechanical stress was investigated, focusing on the incommensurate (IC) phase of K2ZnCl4 with the ferroelectric commensurate (C) phase. The coupling by both external fields is derived theoretically by the Landau theory. In order to prove the theoretical results, the electric field dependence of dielectric constants was studied under the mechanical stress of 0 Mpa, 1.5 MPa and 2.5 MPa. Under the stress of 2.5 Mpa, the electric field dependence of X shows the anomalous behavior from the IC phase, and it corresponds to the phase transition from the IC phase to the pseudo-C phase. Such a behavior suggests the coupling between the polarization and the strain in the IC phase.