Sound wave has been thoroughly studied for centuries as one of the most well-known type of classical waves and close partner of our everyday life. Is there any undiscovered phenomenon associated with sound, especially whether we can find new ways to manipulate sound wave based on ideas inspired from quantum-classical mechanics analogue, has been a well sought-after topic for the last decade.

A new study conducted by Dr Jie Zhu, the Assistant Professor of Department of Mechanical Engineering, and his team has made significant progress towards expanding such investigation. With passive acoustic system, Dr Zhu’s team and his collaborator from Huazhong University of Science and Technology present the first experimental study of PT symmetry physics beyond one dimension. A two-dimensional intrinsic PT symmetric potential is demonstrated with an all passive acoustic metamaterials crystal. As an example, the two-dimensional unidirectional sound focusing effect is experimentally realized.

This progress breaks through the most essential roadblock to observing the evolution of non-Hermitian Hamiltonians respecting PT symmetry with acoustic system: the absence of natural gain medium. This all passive acoustic PT-symmetric material requires no electricity supply nor feedback control mechanism. It provides a much more compact and robust solution, when pushing the PT-symmetry acoustic research into practice in the future to build new devices for sound imaging and sensing.

This work was recently accepted for publication in Physical Review Letters. ME PhD student Tuo Liu is the first author. Dr Jie Zhu is the corresponding author.

Learn more at Physical Review Letters