Suppression of lattice thermal conductivity by mass-conserving cation mutation in multi-component semiconductors

TL;DR

This paper demonstrates that in multi-component semiconductors, lattice thermal conductivity can be suppressed through cation mutation without changing the average atomic mass, by enhancing phonon interactions.

Contribution

It introduces a first-principles approach showing how cation mutation controls thermal conductivity independently of mass and coordination.

Findings

Phonon interactions are enhanced in multi-component materials.

Lattice thermal conductivity can be tuned independently of average mass.

Cation mutation affects phonon scattering mechanisms.

Abstract

In semiconductors almost all heat is conducted by phonons (lattice vibrations), which is limited by their quasi-particle lifetimes. Phonon-phonon interactions represent scattering mechanisms that produce thermal resistance. In thermoelectric materials, this resistance due to anharmonicity should be maximised for optimal performance. We use a first-principles lattice-dynamics approach to explore the changes in lattice dynamics across an isostructural series where the average atomic mass is conserved: ZnS to CuGaS$_2$ to Cu$_2$ZnGeS$_4$. Our results demonstrate an enhancement of phonon interactions in the multernary materials, and confirm that lattice thermal conductivity can be controlled independently of the average mass and local coordination environments.