Exploring 2D Isotope Heterostructures for Atomic-Scale Control of Thermal Radiation

Abstract

Two-dimensional (2D) materials with their characteristic layered structures and weak van der Waals interlayer interactions provide a versatile platform for manipulating emergent phenomena and engineering novel functionalities in the thermal near field. Recently, it has been revealed that the energy-momentum dispersions and photonic density of states of 2D materials can be effectively modulated by isotope engineering. Here, we explore the impact of isotope composition on thermal radiation for 2D heterostructures based on hexagonal boron nitride (hBN). By systematically varying the number of layers, we discover that few-layer hBN amplifies the isotope-induced spectral match and mismatch between the hyperbolic phonon polaritons. The largest isotope effect is observed in monolayer hBN, where the ratio of the heat transfer coefficient between isotopically identical and maximally distinct hBN pairs reaches approximately 300. Interestingly, for emitters and receivers of different layer counts, the heat flux between isotopically distinct hBN pairs can surpass that for identical pairs. Furthermore, we reveal that thermal transport is highly sensitive to the stacking order at sub-10 nm gap sizes, as demonstrated by bilayer isotope heterostructures. Finally, to facilitate experimental study, the substrate and temperature dependence of the isotope effect are investigated. Our findings highlight the unique potential of 2D materials for isotopically engineering near-field thermal radiation with single-atomic-layer precision.