Wave transmission through acoustic lossy barrier by using non-Hermitian complementary metamaterial

Abstract

Complementary metamaterials (CMMs), characterized by negative effective mass density and moduli within a specific frequency range, hold the promise of significantly enhancing wave energy transmission across acoustic barriers. These materials operate by acoustically counteracting the barrier, thus offering an efficient conduit for wave propagation. However, when the intrinsic loss factor of the acoustic barrier is considered, the transmission performance of CMMs experiences a marked decrease. This decrement is notably severe, surpassing the theoretical expectations based solely on acoustic dissipation within the barrier. Delving into the depth of this issue, our research scrutinizes the far-reaching implications of the loss factor on wave transmission and takes a critical step forward by extending the effective properties of the complementary metamaterials from real to complex domain, an approach embodying the concept of non-Hermitian physics. Subsequently, we introduce a non-Hermitian CMM, a groundbreaking solution that maintains high transmittance despite the barrier's loss. It adeptly reconciles the impedance mismatch between the lossy barrier and the background medium, ultimately enabling perfect transmission.