# Strain-driven phonon topological phase transition impedes thermal transport in titanium monoxide

## TL;DR

This study demonstrates how strain-induced topological phonon phase transitions in titanium monoxide can significantly reduce thermal conductivity by breaking symmetry and increasing phonon scattering, offering new ways to control heat transport in materials.

## Contribution

It reveals the impact of topological phonon phase transitions on thermal transport and shows how uniaxial strain can effectively tune thermal conductivity in TiO.

## Key findings

- Applying 10% tension reduces thermal conductivity by up to 77%.
- Symmetry breaking lifts degeneracy of acoustic phonon branches.
- Enhanced phonon scattering increases thermal resistance.

## Abstract

Topological phonon states in crystalline materials have attracted significant research interests due to their importance for fundamental physical phenomena, yet their implication on phonon thermal transport remains largely unexplored. Here, we use density functional theory calculations and symmetry analyses to explore topological phonon phase transitions under uniaxial strains and their tuning effects on thermal transport in titanium monoxide (TiO). Our calculation shows that application of 10% tension significantly diminishes lattice thermal conductivity of TiO by 77% and 66% along the a and c axes, respectively, at room temperature. This suppression is found to result largely from the breaking of symmetry protected degeneracy of acoustic branches, which induces a substantial enhancement of phonon scattering phase space due to the easier fulfillment of scattering selection rules. Our study provides evidence for the importance of phononic band topology in modulating thermal conductivity and offers a promising route towards controlling solid-state heat transport.