Controlling the exceptional points of parity-time symmetric acoustics

Parity-time (PT) symmetric systems experience phase transition between PT “exact” and “broken” phases at exceptional point. These PT phase transitions contribute significantly to the design of single mode lasers, coherent perfect absorbers, isolators, diodes, etc. However, such exceptional points are extremely difficult to access in practice because of the dispersive behavior of most loss and gain materials required in PT symmetric systems. Here, we introduce a method to systematically tame these exceptional points and control PT phases. Our experimental demonstration hinges on an active acoustic element that realizes a complex-valued potential and simultaneously controls the multiple interference in the structure. The manipulation of exceptional points offers new routes to broaden applications for PT symmetric physics in acoustics, optics, microwaves, and electronics, which are essential for sensing, communication, and imaging.