The Thermal Transport in Twin Superlattice: From Phonon Coherence Phenomenon to Anomalous Excitation of High-Energy Phonons at Twin Boundaries

Abstract

Twinning technology has attracted increasing attention due to its ability to endow materials with exceptional mechanical properties. In this study, we investigate the thermal transport properties, which are closely related to mechanical performance, of twin superlattice. The results show that not all superlattice structures formed by twin boundaries (TBs) exhibit enhanced thermal conductivity (TC) due to phonon coherence effects. Among them, only ∑3 twin structure demonstrates a non-monotonic TC trend, however, analysis of the modal contributions to TC reveals that long-wavelength phonons in ∑5 and ∑9 structures also display coherence effects. This confirms the universality of coherence induced by superlattice structures, although the effectiveness of such coherence is influenced by the morphology of TBs. Further in-depth analysis reveals that ∑5 and ∑9 TBs can anomalously excite higher-energy phonons, which demonstrate enhanced delocalization and higher contribution to glass-like TC, this is an effect that positively contributes to thermal transport. Our study reveals the complex thermal transport behaviors of twin structures cannot be fully explained by phonon transport or localization theories alone. This work offers a strong theoretical and data foundation for broadening the application of twinning technology in chip cooling, semiconductor packaging, and other interface-dominated fields.