Nonreciprocal acoustic transmission in space-time modulated coupled resonators

Systems that break reciprocity offer new possibilities for controlling wave propagation. Here we study the scattering properties of coupled resonator systems that are under dynamic modulation. Strong linear nonreciprocal transmission is manifested in the acoustic regime by introducing an initial spatial phase bias to the space-time modulated coupled resonators. A theoretical model is developed to characterize the system and the results are in good agreement with experimental observations. Our work opens up new opportunities for designing compact nonreciprocal devices and developing acoustic topological insulators.