Topologically robust sound propagation in an angular-momentum-biased graphene-like resonator lattice

• Published in: Nature communications Vol. 6; no. 1; p. 8260
• Main Authors: Khanikaev, Alexander B., Fleury, Romain, Mousavi, S. Hossein, Alù, Andrea
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.10.2015; Nature Publishing Group; Nature Pub. Group
• Subjects: 639/301/119/2792; 639/301/357/918; 639/766/25/3927; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms9260

Topological insulators do not allow conduction in the bulk, yet they support edge modes that travel along the boundary only in one direction, determined by the carried electron spin, with inherent robustness to defects and disorder. Topological insulators have inspired analogues in photonics and optics, in which one-way edge propagation in topologically protected two-dimensional materials is achieved breaking time-reversal symmetry with a magnetic bias. Here, we introduce the concept of topological order in classical acoustics, realizing robust topological protection and one-way edge propagation of sound in a suitably designed resonator lattice biased with angular momentum, forming the acoustic analogue of a magnetically biased graphene layer. Extending the concept of an acoustic nonreciprocal circulator based on angular-momentum bias, time-reversal symmetry is broken here using moderate rotational motion of air within each element of the lattice, which takes the role of the electron spin in determining the direction of modal edge propagation. Topological order for sound remains largely unexplored. Here, Khanikaev et al . introduce the concept of topological order in classical acoustics, realizing robust topological protection and one-way edge propagation of sound in a suitably designed resonator lattice, thus expanding the ability to tailor acoustic waves.