Glasslike phonon excitation caused by ferroelectric structural instability

TL;DR

This study reveals that near the ferroelectric phase boundary, Ba1-xSrxAl2O4 exhibits glasslike phonon excitations due to critical acoustic phonon behavior, linking structural instability to amorphous-like properties.

Contribution

It demonstrates the emergence of glasslike phonon excitations caused by ferroelectric structural instability in a crystalline material.

Findings

Enhanced low-energy acoustic phonons near FE phase boundary

Phonon spectrum becomes glasslike and damped near the FE transition

Links structural instability to amorphous-like lattice dynamics

Abstract

Quest for new states of matter near an ordered phase is a promising route for making modern physics forward. By probing thermal properties of a ferroelectric (FE) crystal Ba1-xSrxAl2O4, we have clarified that low-energy excitation of acoustic phonons is remarkably enhanced with critical behavior at the border of the FE phase. The phonon spectrum is significantly damped toward the FE phase boundary and transforms into glasslike phonon excitation which is reminiscent of a boson peak. This system thus links long-standing issues of amorphous solids and structural instability in crystals to pave the way to controlling lattice fluctuation as a new tuning parameter.