Symmetry-breaking strain drives significant reduction in lattice thermal conductivity: A case study of boron arsenide

TL;DR

This study demonstrates that uniaxial tensile strain significantly reduces the lattice thermal conductivity of boron arsenide by altering phonon properties and scattering mechanisms, offering new ways to control heat transport in materials.

Contribution

It reveals that uniaxial strain causes a monotonic decrease in thermal conductivity of BAs, contrasting with isotropic strain effects, and elucidates the underlying phonon scattering mechanisms involved.

Findings

Uniaxial strain reduces BAs thermal conductivity by nearly 80% at room temperature.

Strain lifts phonon band degeneracy and softens phonon spectrum, increasing scattering.

Thermal conductivity suppression is more pronounced perpendicular to the strain direction.

Abstract

Recent research has revealed that cubic boron arsenide (BAs) exhibits a non-monotonic pressure dependence of lattice thermal conductivity ($\kappa_{\rm L}$) under isotropic strain. Here, through rigorous first-principles calculations, we unveil that uniaxial tensile strain induces a monotonic reduction in the $\kappa_{\rm L}$ of BAs -- a striking contrast to the isotropic scenario. The results show that applying uniaxial (100) strain leads to the lifting of phonon band degeneracy, accompanied by an overall softening of the phonon spectrum. These modifications significantly increase phonon-phonon scattering channels by facilitating the fulfillment of selection rules, resulting in a concurrent increase in both three- and four-phonon scattering rates. Consequently, $\kappa_{\rm L}$ exhibits a dramatic suppression of nearly 80\% under large tension at room temperature. Meanwhile, we unexpectedly observe that the uniaxial strain suppresses $\kappa_{\rm L}$ much more strongly in the direction perpendicular to the strain than along the stretching direction. This work establishes the fundamental understanding of the thermal conductivity behavior of BAs under uniaxial strain and opens a promising avenue for manipulating solid-state heat transport by tuning crystal symmetry.