Isotope Effect on Radiative Thermal Transport

Isotope effects on heat conduction and convection have been known for decades. However, whether thermal radiation can be isotopically engineered remains an open question. Here, we first predict up to 4-orders-of-magnitude variation of radiative heat flow with varying isotopic compositions for parallel polar dielectric plates at room temperature. We reveal this as an isotope mass effect which induce phonon line shift and broadening that in turn affect phonon-mediated resonant absorption both in the near and far field. In contrast, the isotope effect is negligible for metals and doped semiconductors which largely depend on free carriers. We also discuss the role of temperature with regard to surface mode excitation. Our work can inject momentum into the isotope physics and provide new pathways to control the nanoscale thermal transport.