Strong Orbital-Lattice Coupling Induces Glassy Thermal Conductivity in High-Symmetry Single Crystal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>BaTiS</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Abstract

In this work, we investigated glassy lattice thermal conductivity in high-symmetry <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mrow><a:mrow><a:mi mathvariant="normal">BaTi</a:mi></a:mrow><a:mrow><a:msub><a:mrow><a:mi mathvariant="normal">S</a:mi></a:mrow><a:mrow><a:mn>3</a:mn></a:mrow></a:msub></a:mrow></a:mrow></a:mrow></a:math> crystals, with a particular focus on the critical interplay between orbital electrons and lattice dynamics. Strong orbital-lattice coupling was found to induce spontaneous symmetry breaking through the Ti-S octahedral distortions, leading to the formation of a unique 1D order–2D disorder lattice structure. With neuroevolution potentials, molecular dynamics simulation of this structure successfully reproduced the glasslike in-plane lattice thermal conductivity observed in experiments. The predicted out-of-plane thermal conductivity decreases with temperature, exhibiting a crystalline trend that is consistent with our measurements. Our findings provide fundamental insights into the mechanism of anomalous amorphous thermal conductivity in single crystals, which arises from the coexistence of overall high symmetry and local structural disorder in specific regions.