Robust nonreciprocal acoustic propagation in a compact acoustic circulator empowered by natural convection

The development of the quantum Hall effect in condensed matter physics that breaks time-reversal symmetry by magnetic biasing has inspired its analog in classical nonreciprocal acoustics. Nonreciprocal acoustic propagation is highly desirable to control acoustics in isolation, broadband unidirectional transmission, and topologically robust to structural disorders or defects. So far, these fascinating properties have been investigated through fan-induced moving media, acoustic capacitance adjustment and acoustic metamaterials. However, these may be associated with disadvantages including extra noise and limited dynamic controlling performance. Here we overcome these limitations by introducing heat-induced natural convection into acoustic circulator, and demonstrate that the classical acoustic circulator with thermal management can realize robust nonreciprocal acoustic propagation. The concept of combining heat-induced natural convection and aeroacoustics creates a new practical paradigm and increases the feasibility for nonreciprocal acoustics due to merits of dynamic control, versatile topological structures, and miniaturization in the absence of moving parts.