Quasi-Ballistic Heat Conduction of Long-Range Surface Phonon Polaritons Coupled to Thermal Reservoirs

Rigorous thermal control at nanoscales has become essential with the miniaturization of electronic devices. However, heat transfer in such structures is hindered by increased boundary scatterings and the reduced thermal conductivity in nanoscales. Surface phonon polaritons (SPhPs), arising from the coupling of optical phonons and photons in the mid-IR regime, present a promising solution as long-range heat carriers, capable of circumventing the limitations faced by traditional heat carriers like acoustic phonons in nanoscales. However, the detection and utilization of SPhP-mediated thermal conduction have proven to be challenging. Here, we introduce an innovative approach that employs a grating-integrated thermometry platform, specifically designed to enhance the transmission of the long-propagating SPhPs, and detectability of SPhPs over short, ballistic distances. We demonstrate quasi-ballistic, length-dependent thermal conduction, achieving a remarkable thermal conductance of 1.5 nW/K, facilitated by long-range SPhPs in one-dimensional SiO₂ heat channels. Our findings pave the way for advanced thermal management in microelectronics by leveraging the novel heat carrier, SPhPs.