Thermal Rectification Mediated by Polaritonic Heat Conduction

The pursuit of advanced thermal management solutions for applications spanning electronics, buildings, and energy conversion/storage has intensified with the exploration of thermal rectification. While previous studies have several approaches using phase-change materials, heterostructures, or mechanical deformation, thermal rectification ratios have consistently lagged behind those observed in electrical or optical transport. This challenge origins from the diffusive nature of heat conduction mediated by classical heat carriers, e.g., phonons and electrons. Here, we leverage surface phonon polaritons (SPhPs), a coupled energy carrier arising from the interaction between optical phonons and photons, to enhance thermal rectification. Theoretical predictions suggest that these distinctive heat carriers exhibit anomalously long propagation length over 100s μm. In our study, various long and thin polar dielectric nanostructures, e.g., SiO₂ nanowalls, were designed and integrated into a suspended thermometry platform to facilitate the probe of polaritonic thermal conductance. To demonstrate the asymmetric heat transfer across forward and reverse directions, we controlled the coupling coefficient of surface-guided waves by incorporating grating structures into one side of the thermometry platform. In this presentation, we will discuss the rationale behind the design of nanostructured heat channels and thermometers, showcasing their critical role in realizing asymmetric transmittance of quasi-ballistic heat transport.