Origins of Giant Anisotropic Phonon Heat Transfer in True‐1D van der Waals Material

Abstract Thermal rectification devices, which facilitate preferential heat flow in a singular direction, stands as pivotal tools in the realization of solid‐state thermal circuits. 1D atomic chains, exhibit heightened thermal rectification efficiency owing to their exceptional directional heat conduction properties. These will find widespread utility in many applications, encompassing areas such as cooling, energy harvesting, and thermal isolation systems. However, unlike quasi‐1D materials, the intrinsic anisotropic heat transport in true‐1D atomic chains is yet to be systematically studied. Herein, the origins of the anisotropic heat transfer in three representative 1D structures (TaSe 3 and BaTiS 3 marked as quasi‐1D, MoI 3 labeled as true‐1D) is first investigated by integrating a first‐principles density functional theory‐based framework of two‐channel heat conduction model. In contrast to quasi‐1D, MoI 3 exhibits a giant anisotropy of lattice thermal conductivity ( κ L ) in chain‐ and cross chain‐directions with a high ratio up to ≈20, which far exceeds the previous report for HfTe 5 and ZrTe 5 . Such unique heat transfer reveals comprehensively by charge‐sharing and transferred charges, p‐ ‐ d orbital hybridization and Young's modulus changes, induces an exceptionally large anisotropy. This study presents a high‐performance implementation of thermal rectification designed to regulate directional heat current, demonstrating its potential applicability in solid‐state thermal circuits.