Phonon soft modes and para- to ferroelectric phase transitions

TL;DR

This paper reviews the theory of soft phonons with nonlinear interactions and applies it to understand the para- to ferroelectric phase transition in BaTiO3, highlighting the role of phonon soft modes.

Contribution

It introduces a theoretical framework for soft phonons with quartic nonlinearities and applies it specifically to BaTiO3's phase transition, offering insights into ferroelectric behavior.

Findings

Identification of soft phonon modes in BaTiO3

Role of nonlinear interactions in phase transition

Theoretical explanation of para- to ferroelectric transition

Abstract

In this special issue of Physica A in memory of Professor Dietrich Stauffer, I first recall my impression on him while being his postdoc for a year at HLRZ. In the following scientific part, I discuss the theory of soft phonons with quartic nonlinear interactions. This is applied to the cubic crystal BaTiO$_3$ for phase transition from para- to ferroelectric phase.