Nonlocal Acoustic Moiré Hyperbolic Metasurfaces

Abstract

The discovery of the topological transition in twisted bilayer (tBL) materials has attracted considerable attention in nano‐optics. In the analogue of acoustics, however, no such topological transition has been found due to the inherent nondirectional scalar property of sound pressure. In this work, by using a theory‐based nonlocal anisotropic design, we transform the in‐plane acoustic pressure into a spatially distributed vector field using twisted multilayer metasurfaces. So‐called “acoustic magic angle”‐related acoustic phenomena occur, such as nonlocal polariton hybridization and the topological Lifshitz transition. The dispersion becomes flat at the acoustic magic angle, enabling polarized excitations to propagate in a single direction. Moreover, the acoustic topological transition (from hyperbolic to elliptic dispersion) is experimentally observed for the first time as the twist angle continuously changes. This unique characteristic facilitates low‐loss tuneable polariton hybridization at the subwavelength scale. We also experimentally demonstrate a twisted trilayer acoustic metasurface, and find more possibilities for manipulating acoustic waves. These discoveries not only enrich the concepts of moiré physics and topological acoustics but also provide a complete framework of theory and methodologies for explaining the phenomena we observed.This article is protected by copyright. All rights reserved

Twist-induced Casimir Attractive-Repulsive Transition Based on Lithium Iodate

“…Twisted systems are characterized by their unique physical properties resulting from the relative rotational angles in multilayer structure. − In these systems, the twisting of the layers alters the electronic structure and optical properties of the materials, leading to a range of novel quantum phenomena. For instance, in bilayer graphene systems, superconductivity can be induced when the twist angle reaches a “magic angle”. , These phenomena are crucial for exploring new physical states and for advancing technological developments.…”