Unidirectional Negative Refraction at an Exceptional Point of Acoustic PT-Symmetric Systems

Abstract

In this work, we demonstrate a method to realize the unidirectional negative refraction in an acoustic parity-time (PT)-symmetric system, which is composed of a pair of metasurfaces sandwiching an air gap. The pair of metasurfaces possesses loss and gain modulations, respectively. The unidirectional negative refraction, which is strictly limited to the case of incident wave imposing on the lossy end of the metasurface, is demonstrated at the exception point (EP) in this PT-symmetric system, while the incidence from the other side will lead to strong reflection. Based on the rigorous calculations, we explicitly show the underlying mechanism of this model to achieve unidirectional wave scatterings around the EP in the parametric space. In addition, the perfect imaging of a point source in the three-dimensional space, as a signature of negative refraction, is simulated to provide a verification of our work. We envision that this work may sharpen the understanding of PT-symmetric structures and inspire more acoustic functional devices.

Localization Dynamics at the Exceptional Point of Non-Hermitian Creutz Ladder

“…[14][15][16] The EPs in non-Hermitian physics have found extensive applications in optical sensing, [17][18][19][20][21][22][23] robust energy transfer, [24] and unidirectional dynamics. [25][26][27][28][29][30][31][32][33][34] Photonic structures are favorable in the investigation of the non-Hermitian physics. Recent advances in non-Hermitian physics have highlighted deviations from the established principle of bulk-boundary correspondence, [35][36][37][38] with new phenomena such as the non-Hermitian skin effect fundamentally changing the understanding of edge states.…”