Brillouin Scattering of Paraelectric KH2PO4 under Applied Uniaxial Stress

Abstract

The Brillouin scattering spectra of XY shear phonon in KH2PO4 under an applied XY shear stress have been studied in the neighborhood of the ferroelectric transition temperature. The acoustic phonon is overdamped near Tc, but become underdamped under the applied shear stress. The observed increase of elastic constant C66 with increasing XY shear stress is similar to dependence on electric fields. In the case of ΔT(≡T-Tc)<∼0.05 K, application of stress caused a transition not to have a soft acoustic phonon.