A Unfied Thermal Transport Picture Across Phases via Spatiotemporal Coherence

The coherence of lattice vibrations in crystals, quantized by phonons, significantly influences thermal transport and its vibrational characteristics in dfferent states of aggregates, extending alike to complex and amorphous matters. However, understanding how transport mechanisms vary with disorder across phases of matters from a common picture of coherence remains a critical issue. Particularly, we unveil that the non-monotonic dependence of thermal conductivity on temperature across different phases in general is governed by spatiotemporal coherence. Our wavelet transform approach demonstrates that spatiotemporal coherence diminishes in the transition from solid to liquid but in contrast is unexpectedly reversely enhanced from liquid to gas, resulting in a delayed dissipation of thermal energy and thereby increasing the thermal conductivity. We emphasize that this enhancement is initiated by atomic diffusion during the phase transition. The general behavior of thermal vibrations and conduction across phases is explained via those underlying drastic changes in the coherence nature of heat carriers, which is crucial for understanding and predicting thermal transport features from a uni ed perspective.