Fragile topologically protected perfect reflection for acoustic waves

Abstract

The paper reveals that acoustical topological edge states can be perfectly reflected by a coupled acoustic cavity as long as its resonant frequency falls into the topological band gap. This perfect reflection is protected by the system topology and thus robust against the fabrication defects, behaved as the topologically protected perfect reflection (TPPR). The TPPR paves the way for broad applications of topology in acoustic, such as topological acoustic switches, sensors, and phase modulators.