Single-channel or multi-channel thermal transport? Effect of higher-order anharmonic corrections on the predicted phonon thermal transport properties of semiconductors

TL;DR

This study demonstrates that including higher-order anharmonic corrections significantly alters the predicted phonon thermal conductivities of semiconductors, revealing the importance of multi-channel transport analysis for accurate modeling.

Contribution

The paper introduces a higher-order theoretical framework for phonon thermal transport, highlighting its necessity over lowest-order models for accurate predictions in semiconductors.

Findings

Lower thermal conductivities (<0.5 W/m-K) in several compounds at 300 K.

Higher-order corrections can both increase or decrease thermal conductivity.

Wave-like coherent transport contributes less than 0.05 W/m-K in ultra-low conductivity materials.

Abstract

The phonon thermal transport properties of eight ternary intermetallic semiconductors are investigated by accounting for higher-order four-phonon scattering, phonon renormalization, and multi-channel thermal transport. The commonly used lowest-order theory, which accounts only for three-phonon scattering and without phonon renormalization, fails drastically for considered materials and underpredicts the thermal conductivity by up to a factor of two. The thermal conductivity decreases for three compounds and increases for five compounds with the application of higher-order corrections owing to a contrasting role of four-phonon scattering and phonon stiffening on the predicted thermal conductivity. Using the higher-order theory, at a temperature of 300 K, the lowest obtained thermal conductivity is 0.31 W/m-K for BiCsK2 and three other compounds (SbCsK2, SbRbNa2, and SbRbK2) have thermal conductivities lower than 0.5 W/m-K via the particle-like phonon transport channel. The contribution from the wave-like coherent transport channel is lower than 0.05 W/m-K in all of these ultra-low thermal conductivity compounds. The higher-order theory is a must for the correct description of thermal transport physics, failing which the thermal transport is wrongly characterized as multi-channel transport by the lowest-order theory.