Far-field heat transfer and monochromatic thermal currents in a cylindrical nonreciprocal cavity

TL;DR

This paper explores how breaking Kirchhoff's law in cylindrical cavities enables controlled, directional heat transfer and monochromatic currents, with potential applications in thermal management and nonreciprocal photonic devices.

Contribution

It demonstrates the effects of nonreciprocal materials on far-field heat transfer, revealing tunable rectification and circulation, and introduces a specular ray-tracing method for analysis.

Findings

Violation of Kirchhoff's law causes non-zero heat rectification coefficients.

Internal monochromatic currents vanish at equilibrium but can be controlled out of equilibrium.

Rotational heat fluxes can be precisely manipulated using reciprocal and nonreciprocal materials.

Abstract

Breaking Kirchhoff's law of thermal radiation yields new opportunities in one-way radiative thermal transport and circuitry. We investigate its consequences in the far-field regime in cylindrical cavities, by employing a specular ray-tracing algorithm. At thermal equilibrium, we show that violation of Kirchhoff's law yields non-vanishing heat rectification coefficients within different sections of the cavity, which can be tuned for perfect rectification and circulation, while internal monochromatic currents vanish due to the intrinsic coupling between emission and absorption at specular surfaces. This constraint is lifted under nonequilibrium conditions, where rotational heat fluxes within the cavity can be precisely controlled by appropriately combining reciprocal and nonreciprocal materials. These findings open new avenues for thermal management and provide design principles for nonreciprocal photonic devices.