Ultrahigh-contrast and large-bandwidth thermal rectification in near-field electromagnetic thermal transfer between nanoparticles

We exploit the unique properties of optical waves in nanophotonic structures to enhance the capabilities for active control of electromagnetic thermal transfer at nanoscale. We show that the near-field thermal transfer between two nanospheres can exhibit a thermal rectification effect with very high contrast and large operating bandwidth. In this system, the scale invariance properties of the resonance modes result in a large difference in the coupling constants between relevant modes in the forward and reverse scenarios. Such a difference provides a mechanism for thermal rectification. The two-sphere system can also exhibit negative differential thermal conductance.