Synthetic exceptional points and unidirectional zero reflection in non-Hermitian acoustic systems

Exceptional points (EPs) are responsible for a number of interesting phenomena in non-Hermitian wave systems. Here we show, both theoretically and experimentally, that EPs can be synthesized in non-Hermitian acoustic systems with unbalanced loss factors in different sections. Numerical simulations and measurements confirm that unidirectional zero reflection, one of the hallmarks of EPs, can be realized in such a compact system with controlled Willis coupling and loss. When approached from one direction in the parameter space, the material slab mimics a conventional parity-time (PT) symmetric system. Our findings provide an efficient way for advanced engineering of scattering properties of artificial acoustic materials with EP-related physics.