Acoustic chiral mode transfer for symmetry-broken states in anti-parity-time symmetric systems

Dynamic encircling of an anti-parity-time (anti-PT) symmetric exceptional point (EP) leads to chiral transfer of symmetry-broken modes, which has been explored in various systems except acoustics. In this work, acoustic counterpart of this behavior is numerically demonstrated in coupled waveguide systems with anti-PT-symmetric EPs. The model consists of three coupled waveguides designed to mimic a three-state system that can be described by the coupled mode theory. By adiabatically eliminating the intermediate state with high loss, the anti-PT symmetry and associated EP can be formed in an effective system comprising the remaining two states. According to the parametric path enclosing the EP, acoustic propagation model is designed to support the space-driven acoustic mode evolution. Numerical simulations are conducted to demonstrate acoustic chiral transfer of symmetry-broken states.