Valley Topological Phases In Bilayer Sonic Crystals

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Abstract

Recently, the topological physics in artificial crystals for classical waves has become an emerging research area. In this Letter, we propose a unique bilayer design of sonic crystals that are constructed by two layers of coupled hexagonal array of triangular scatterers. Assisted by the additional layer degree of freedom, a rich topological phase diagram is achieved by simply rotating scatterers in both layers. Under a unified theoretical framework, two kinds of valley-projected topological acoustic insulators are distinguished analytically, i.e., the layer-mixed and layer-polarized topological valley Hall phases, respectively. The theory is evidently confirmed by our numerical and experimental observations of the nontrivial edge states that propagate along the interfaces separating different topological phases. Various applications such as sound communications in integrated devices can be anticipated by the intriguing acoustic edge states enriched by the layer information.

Description

Includes supplementary material

Keywords

Graphene, Photonic crystals, Phase diagrams, Brillouin zones, Dirac equation, Quantum Hall effect

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National Basic Research Program of China (Grant No. 2015CB755500); National Natural Science Foundation of China (Grants No. 11704128, No. 11774275, No. 11674250, No. 11534013, and No. 11747310); National Postdoctoral Program for Innovative Talents (BX201600054); China Postdoctoral Science Foundation (2017M610518)

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©2018 American Physical Society

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