Electric field-dependent phonon spectrum and heat conduction in ferroelectrics

Area of Science:

• Condensed matter physics
• Materials science
• Thermodynamics

Background:

• Thermal conductivity in ferroelectrics is primarily governed by phonons.
• Understanding phonon behavior is crucial for controlling thermal properties.
• Previous studies suggested field-dependent phonon scattering influenced thermal transport.

Purpose of the Study:

• To experimentally investigate the effect of external electric fields on phonon velocity, thermal conductivity, and diffusivity in lead zirconium titanate-based ferroelectrics.
• To elucidate the underlying mechanisms responsible for field-induced changes in thermal transport.
• To develop a theoretical model explaining these observed phenomena.

Main Methods:

• Experimental measurements of phonon velocity, thermal conductivity, and diffusivity under an external electric field.
• Analysis of phonon dispersion and scattering mechanisms.
• Development and application of a quantitative theoretical model.

Main Results:

• External electric fields significantly affect longitudinal acoustic phonon velocity, thermal conductivity, and diffusivity.
• Observed changes are attributed to alterations in phonon dispersion, not scattering.
• A theoretical model accurately predicts these field dependencies without adjustable parameters.

Conclusions:

• Phonon dispersion is the key mechanism for electric-field-induced thermal transport modulation in ferroelectrics.
• Identified 'ferrons' as heat- and polarization-carrying phonons.
• The findings pave the way for electrically driven all-solid-state heat switches and improved solid-state heat engines.