Theory of many-body radiative heat transfer without the constraint of reciprocity

Understanding electromagnetic heat transfer in many-body systems is critical to exploring new physics effects that can arise in reciprocal and nonreciprocal many-body systems. Here, the authors develop explicit and compact formulas for electromagnetic heat transfer in systems consisting of a large number of bodies without the constraint of reciprocity. They go on to demonstrate the emergence of a persistent heat current at thermal equilibrium and a directional heat flow at nonequilibrium in systems composed of multiple magneto-optical particles. This opens up possibilities for controlling near-field electromagnetic heat transfer using complex reciprocal and nonreciprocal systems.