Thermal Transport at Reduced Dimensions: From Fundamentals to Functional Materials

ABSTRACT: As device dimensions shrink and power densities increase in post-Moore electronics, thermal transport has become a critical challenge for next-generation technologies. At reduced dimensions, classical Fourier heat conduction becomes inadequate due to phonon confinement, interfacial scattering, and quantum effects. This review summarizes recent advances in phonon-mediated thermal transport in low-dimensional materials, particularly two-dimensional (2D) materials and van der Waals (vdW) heterostructures. Fundamental mechanisms, including phonon scattering, dimensional confinement, and interfacial thermal resistance, are discussed together with representative 2D systems such as graphene, hexagonal boron nitride, transition metal dichalcogenides, and black phosphorus. Particular attention is devoted to interfacial thermal transport and twist-angle-dependent phonon engineering in vdW heterostructures, which enable effective control of thermal transport through tunable interlayer coupling. Emerging phenomena, including phonon hydrodynamics and asymmetric thermal transport, are also highlighted. In addition, the growing role of materials informatics and machine learning in designing thermal functional materials is discussed. By connecting fundamental phonon physics with data-driven materials engineering, this review provides perspectives for thermal management, thermoelectric energy conversion, and next-generation energy-efficient technologies.