Acoustic suppressed topological refraction in valley sonic crystals

Abstract

We report both experimentally and numerically that an acoustic suppressed topological refraction is realized by two kagome-lattice valley sonic crystals (VSCs). By simply rotating triangle rods in the VSCs, acoustic valley Hall phase transitions can be obtained. In a designed topological waveguide composed of two VSCs with distinct valley topological phases, two types of valley edge states can be observed in the domain wall. Furthermore, the topological waveguide can support a suppressed topological refraction of sound, which arises from the excitation of an acoustic dipole mode at the exit of the domain wall. Such a phenomenon is experimentally demonstrated by scanning topological refractions of the edge states from a zigzag termination, in which the theoretical prediction of a negative refraction almost overlaps with the perpendicular bisector of the dipole mode, and thus it is suppressed totally. Finally, the robustness of the suppressed topological refraction is demonstrated experimentally. Our work can find potential applications in designing the devices of robust directional sound transports and communications.

Theory of complex-coordinate transformation acoustics for non-Hermitian metamaterials

“…Non-Hermitian physics can be verified by using acoustics and electromagnetics, which not only provide a better understanding [20][21][22] but also bring non-Hermitian physics closer to practical applications. [23,24] Several interesting re-searches have shown unique features of exceptional point and exceptional ring [25,26] and the extraordinary capabilities in manipulating wavefronts asymmetrically. [27][28][29] Recent explorations of loss and gain within the framework of non-Hermitian systems play important roles in controlling acoustic transport, especially amplitude modulation.…”

Manipulation of elastic wave by reconfigurable elastic topological waveguide

“…of valley pseudospin into the subfields of physics, such as photonics [1][2][3][4][5][6][7][8][9][10][11], acoustics [12][13][14][15][16][17][18][19][20][21][22], and mechanics . In the field of mechanics, by breaking the mirror [27,29,39,43] or inversion [23-26, 28, 30-38, 40-42, 44] symmetry, the band inversion and valley Hall phase transitions caused by elastic phononic crystals (EPCs) have been realized, and the edge states which support robust topological valley transports can be observed at a domain wall (DW) between the two EPCs with opposite valley Chern numbers.…”