Optical phonon contribution to the thermal conductivity of a quantum paraelectric

TL;DR

This paper investigates how quantum critical optical phonons influence thermal conductivity in paraelectric materials, revealing a low-temperature power law behavior that aligns with experimental observations and highlights quantum fluctuations' role.

Contribution

It introduces a theoretical calculation of optical phonon contributions to thermal conductivity near a quantum critical point, emphasizing quantum fluctuations' significance.

Findings

Thermal conductivity follows a $T^{eta}$ power law with $1<\beta<2$ at low temperatures.

Results agree with recent experimental data.

Quantum fluctuations significantly affect thermal transport in paraelectrics.

Abstract

Motivated by recent experimental findings, we study the contribution of a quantum critical optical phonon branch to the thermal conductivity of a paraelectric system. We consider the proximity of the optical phonon branch to transverse acoustic phonon branch and calculate its contribution to the thermal conductivity within the Kubo formalism. We find a low temperature power law dependence of the thermal conductivity as $T^{\alpha}$, with $1 < \alpha < 2$, (lower than $T^3$ behavior) due to optical phonons near the quantum critical point. This result is in accord with the experimental findings and indicates the importance of quantum fluctuations in the thermal conduction in these materials.