Broadband topological valley transport of elastic wave in reconfigurable phononic crystal plate

Abstract

Topological insulators have attracted intensive attention due to their robust properties of path defect immunity, with diverse applications in electromagnetic, acoustic, and elastic systems. The recent development of elastic topological insulators (ETIs), based on artificially structured phononic crystals, has injected new momentum into the manipulation of elastic waves. Earlier ETIs with unreconfigurable geometry and narrow frequency bandgaps hinder the exploration and design of adaptable devices. In this work, a tunable phononic crystal plate with Y-shaped prisms is designed to support valley transport of elastic waves, based on the analogy of the quantum valley Hall effect. By rotating the prisms to reconstruct the configuration, the mirror symmetry is broken to open a new bandgap. Based on this characteristic, we design an interface between two ETIs with different symmetry-broken geometries, which supports topologically protected edge states. We further design a reconfigurable device for elastic wave channel switching and beam splitting and demonstrate it both numerically and experimentally. In addition, in order to meet the requirement of the wide frequency range, the genetic algorithm is adopted to optimize the geometry so as to achieve the broadband valley transportation of elastic waves. The results obtained in this paper can promote the practical applications of tunable broadband elastic wave transmission.

Underwater metamaterial absorber with impedance-matched composite

“…The absorption performance of a large-size sample was verified by measurements in a water pool, with an averaged absorption of 90.3% from 4 kHz to at least 20 kHz. The materials and the design methodology adopted in this work may provide a new route in designing versatile devices with broadband features, such as camouflage stealth materials ( 2 , 3 , 54 ), tunable waveguides ( 55 , 56 ), metamaterial-based lens ( 8 , 57 , 58 ), impedance transformer ( 59 , 60 ), etc.…”

Conceptual-based design of an ultrabroadband microwave metamaterial absorber

“…Our absorber breaks this limit by introducing self-similar structures attendant with the absorption of the diffracted beams by dissipative foam, thereby extending the absorption capability to a much higher frequency regime. The basic conceptual elements adopted in this work may have potential in designing versatile devices with broadband performance, such as tunable waveguides ( 55 – 57 ), electromagnetic cloak ( 58 , 59 ), metamaterial-based antenna ( 60 ), achromatic metalens ( 61 ), etc.…”

Progress in Topological Mechanics

“…A new degree of freedom, valley, has been introduced into the classical wave systems. The QVHE has been theoretically and experimentally demonstrated in photonic crystals [38][39][40][41]84,85], sonic crystals [42,49,50,53] and mechanical structures [55,[69][70][71][72][73][74][75][76][77][78][79]86,87]. In particular, topologically valley-polarized states in elastic systems have been proposed via bi-layered lattices [69,74], hexagonal lattices [55,70,73,[75][76][77][78][79][88][89][90] and triangular lattices [71,72,86].…”