Dynamical Susceptibility in KDP-type Crysals above and below Tc II

TL;DR

This paper uses the path probability method to analyze the dynamical susceptibility of KH2PO4-type ferroelectric crystals, explaining the dip structure at Tc and matching experimental light scattering data.

Contribution

It applies the PPM in the tetrahedron-cactus approximation to derive dynamical susceptibility features in KDP-type crystals, highlighting the finite relaxation times at the transition.

Findings

Identifies a dip in the real part of susceptibility at Tc.

Calculates the light scattering intensity and central peak structure.

Shows consistency with Raman scattering experiments.

Abstract

The path probability method (PPM) in the tetrahedron-cactus approximation is applied to the Slater-Takagi model with dipole-dipole interaction for KH2PO4-type hydrogen-bonded ferroelectric crystals in order to derive a small dip structure in the real part of dynamical susceptibility observed at the transition temperature Tc. The dip structure can be ascribed to finite relaxation times of electric dipole moments responsible for the first order transition with contrast to the critical slowing down in the second order transition. The light scattering intensity which is related to the imaginary part of dynamical susceptibility is also calculated above and below the transition temperature and the obtained central peak structure is consistent with polarization fluctuation modes in Raman scattering experiments.