Nonreciprocal Heat Circulation Meta-Devices.

Thermal nonreciprocity typically stems from nonlinearity or spatiotemporal variation of parameters. However, constrained by the inherent temperature-dependent properties and the law of mass conservation, previous works were compelled to treat dynamic and steady-state cases separately. Here, by establishing a unified thermal scattering theory, we report the creation of a convection-based thermal meta-device which supports both dynamic and steady-state nonreciprocal heat circulation. We observe the non-trivial dependence between the nonreciprocal resonance peaks and the dynamic parameters, and reveal the unique nonreciprocal mechanism of multiple scattering at steady state. This mechanism enables thermal nonreciprocity in the initially quasi-symmetric scattering matrix of our three-port meta-device, and has been experimentally validated with a significant isolation ratio of heat fluxes. Our findings establish a framework for thermal nonreciprocity that can be smoothly modulated for dynamic and steady-state heat signals, it may also offer insight into other heat-transfer-related problems or even other fields such as acoustics and mechanics. This article is protected by copyright. All rights reserved.