On the dielectric susceptibility calculation in the incommensurate phase of K_2SeO_4

TL;DR

This paper revises the calculation of dielectric susceptibility in the incommensurate phase of K_2SeO_4 by including the local Lorentz electric field, leading to different phase transition predictions from previous models.

Contribution

It introduces a modified thermodynamic potential accounting for the local Lorentz electric field, changing prior susceptibility calculations and phase transition outcomes.

Findings

Revised dielectric susceptibility calculation for K_2SeO_4 in IC phase.

Identification of the impact of local electric fields on phase transition predictions.

Correction of previous models' results regarding ferroelectric IC phase.

Abstract

It is shown that the thermodynamic potential of the domain-like incommensurate (IC) phase of the K_2SeO_4 crystal should be supplemented with a term, taking into account the local, Lorentz electric field. The latter qualitatively changes the result of calculation of the dielectric susceptibility for this IC structure by Nattermann and Trimper, J. Phys. C: Solid State Phys. 14, 1603, (1981), and gives phase transition to the ferroelectric IC phase obtained by Aslanyan, Phys. Rev. B 70, 024102, (2004).