Dimensional crossover in thermal radiation: From three-to two-dimensional heat transfer between metallic membranes

Abstract

Based on fluctuational electrodynamics, we reveal a dimensional crossover in far-field thermal radiation between subwavelength gold membranes. As the membrane thickness decreases from the bulk to the nanoscale, we observe a transition from three-dimensional to two-dimensional heat transfer, which is characterized by a distinct minimum plateau in thermal conductance for intermediate subwavelength thicknesses. This behavior, absent in polar dielectrics, stems from the coupling and decoupling of long-range surface plasmon-polariton modes. The thermal conductance exhibits a T^3 dependence for thick membranes at high temperature and transitions to a T^2 dependence for ultrathin films at low temperature, reflecting the dimensional shift in the photon density of states. Notably, the minimum plateau falls below the black-body limit, demonstrating the potential for tailoring far-field thermal radiation in metallic nanostructures through dimensional confinement and plasmonic effects.

Physical Review Applied 22, L031006 (2024)