Isotope effect on radiative thermal transport: From two-body to many-body systems

Recent studies show that isotope engineering can lead to orders-of-magnitude variations of thermal radiation between two parallel plates. Considering the complexities introduced by many-body interactions, here we explore how the isotope effect on radiative thermal transport varies upon transition from two-body to many-body systems. A variety of basic geometrical configurations consisting of plates and particles are considered. With cubic boron nitride as a representative material, we demonstrate that the isotope effect in many-body systems can reach beyond ${10}^{4}$, which exceeds the maximum value in the parallel-plate geometry by more than sixfold. In addition, we find that for objects of different geometries, the radiative heat flow between isotopically identical materials is not necessarily the largest. These observations are attributed to the distinct and isotope-dependent phonon polaritons of the particles and plates, together with the configurational resonances between multiple closely spaced objects. We also systematically analyze the influence of a few geometrical parameters including the particle-particle distance, particle-plate distance, and plate thickness, as well as some key material properties. Our findings highlight the richness of isotope physics and provide an avenue for controlling thermal transport in many-body systems.