Impurity-induced multi-bit acoustic topological system

Abstract

Acoustic topological insulators (ATIs) are known to own topologically protected properties similar to their electronic and optical counterparts. However, for the topological insulators (TIs) with intact time-reversal symmetry (TRS), some severe defects can also induce strong backscattering. Many works try to avoid the effects of defects on topological wave transport, merely works explore the functions of the defects. Here, based on the interactions between the impurity and topological edge states, we investigate and experimentally demonstrate the capability of impurity to control and switch the valley Hall edge modes in acoustic systems. The results show the acoustic transmission spectrum is sensitive to the rotation angle of the impurity, which can be regarded as a potential platform for switchable acoustic devices or filters. Based on these discoveries, a multi-bit acoustic transmission system is designed by introducing multiple impurities into a multichannel structure, where the acoustic flows to a designated channel can be controlled by rotating impurities. Our experimental measurements match well with simulation results. The results demonstrated in this paper add a new degree of freedom in controlling ATIs and will expedite the progress of programmable acoustic information processing technology. The method of controlling topological wave transmission by impurity operations can also be applied to other systems.