Nonreciprocity and isolation induced by an angular momentum bias in convection-diffusion systems

Inspired by the electronic and acoustic Zeeman effects in wave systems, we demonstrate here that an angular momentum bias generated by a volume force can also lead to modal splitting in convection-diffusion systems but with different features. We further reveal the thermal Zeeman effect by studying the temperature propagation in an angular-momentum-biased ring with three ports (one for input and two for output). In the presence of an optimal volume force, temperature propagation is allowed at one output port but isolated at the other, so rectification coefficient can reach a maximum value of 1. The volume forces corresponding to rectification coefficient peaks can also be predicted by scalar (i.e., temperature) interference quantitatively. Compared with existing mechanisms of thermal nonreciprocity, an angular momentum bias does not require temperature-dependent and phase-change materials, which has an advantage in wide-temperature-range applicability. These results may provide insights into thermal stabilization and thermal topology. The related mechanism is also general for other convection-diffusion systems such as mass transport, chemical mixing, and colloid aggregation.