Waveguides induced by replacing defects in phononic crystal

Abstract

Phononic crystal, the artificial material, has shown the ability to guide the waves. In this paper, we theoretically and experimentally realize interface transports by doping replacing defects in the acoustic valley insulators. Each cell of the valley insulators has a large resonator and a small resonator. The valley insulators exhibit a complete band gap. The bands are divided into two groups respectively below and above the gap. If the small resonators are replaced by the large resonators, the bands above the gap, will move down and submerge into the valley band gap. If the large resonators are replaced by the small resonator, the bands below the gap, will move up and submerge into the valley band gap. The eigenmodes of the evolving bands show that the acoustic pressure energy is concentrated on the interfaces formed by the replacing defects. The frequency-selective transports can be induced by the band evolution. The replacing defects can be doped everywhere in the bulk, forming various waveguides completely wrapped by the valley insulators. Our works reveal the mechanism of guiding waves by the replacing defects in the acoustic valley insulator. The replacing defects can be doped conveniently and can manipulate the waves flexibly.