Nonreciprocity via nonlinearity-enabled all-acoustic spatiotemporal modulation

Acoustic nonreciprocity has attracted attention for its potential in designing logic devices. One way to break reciprocity is by breaking the time-reversal symmetry by spatiotemporally (ST) altering a system's material properties. In the present study, we derive the equations of motion for a discrete non-linear spatiotemporal modulated spring mass system, where the shear stiffnesses are non-linearly dependent on the longitudinal deformations, and produce a physical realization of such a system. We also provide the geometric design with constraints such that we can control the relative speed and coupling strength of the longitudinal and shear waves, as well as the nonreciprocal band structure. Finally, we will present experimental measurement and numerical simulations of nonrecirpocal acoustic wave propagation in this system.