Nonlocal Acoustic Moiré Hyperbolic Metasurfaces

Nonlocal Acoustic Moiré Hyperbolic Metasurfaces

2024 | Chenglin Han, Shida Fan, Changyou Li, Li-Qun Chen, Tianzhi Yang, and Cheng-Wei Qiu
This study presents the experimental realization of a nonlocal acoustic Moiré hyperbolic metasurface, demonstrating a topological transition in twisted bilayer (tBL) acoustic systems. By using a nonlocal anisotropic design, the in-plane acoustic pressure is transformed into a spatially distributed vector field, enabling phenomena such as nonlocal polariton hybridization and the topological Lifshitz transition. The dispersion becomes flat at the "acoustic magic angle," allowing polarized excitations to propagate in a single direction. The acoustic topological transition from hyperbolic to elliptic dispersion is experimentally observed as the twist angle changes, enabling low-loss tunable polariton hybridization at the subwavelength scale. A twisted trilayer acoustic metasurface is also demonstrated, expanding the possibilities for acoustic wave manipulation. These findings enrich the concepts of moiré physics and topological acoustics, providing a complete framework for understanding acoustic phenomena. The tBL system, consisting of nonlocal anisotropic moiré acoustic metasurfaces, allows an in-plane topological transition of acoustic waves under broadband conditions by adjusting the twist angle. The topological transition is determined by the integer number of anticrossing points (N_ACP) in reciprocal space. The dispersion curves change from hyperbolic to elliptic as the twist angle increases, leading to a controlled topological transition. The results show that the dispersion curve becomes flat at a specific angle, enabling low-loss polariton propagation. The acoustic magic angle is defined as the angle where the dispersion curve becomes flat, enabling highly directional propagation. The study also demonstrates the H2E topological transition in a tTL system, extending the frequency range of the topological transition and providing additional degrees of freedom for controlling energy conduction. Theoretical and experimental results show that the tBL system can achieve a topological transition over a wide frequency range, with the dispersion curves becoming flat at the acoustic magic angle. The study also demonstrates the H2E topological transition in a tTL system, extending the frequency range of the topological transition and providing additional degrees of freedom for controlling energy conduction. The results confirm the acoustic equivalence of the Lifshitz transition from the hyperbolic to elliptic phase. The study provides a framework for designing and understanding acoustic metasurfaces, with potential applications in various systems, including those with twisted hyperbolic metasurfaces and anisotropic acoustic impedances.This study presents the experimental realization of a nonlocal acoustic Moiré hyperbolic metasurface, demonstrating a topological transition in twisted bilayer (tBL) acoustic systems. By using a nonlocal anisotropic design, the in-plane acoustic pressure is transformed into a spatially distributed vector field, enabling phenomena such as nonlocal polariton hybridization and the topological Lifshitz transition. The dispersion becomes flat at the "acoustic magic angle," allowing polarized excitations to propagate in a single direction. The acoustic topological transition from hyperbolic to elliptic dispersion is experimentally observed as the twist angle changes, enabling low-loss tunable polariton hybridization at the subwavelength scale. A twisted trilayer acoustic metasurface is also demonstrated, expanding the possibilities for acoustic wave manipulation. These findings enrich the concepts of moiré physics and topological acoustics, providing a complete framework for understanding acoustic phenomena. The tBL system, consisting of nonlocal anisotropic moiré acoustic metasurfaces, allows an in-plane topological transition of acoustic waves under broadband conditions by adjusting the twist angle. The topological transition is determined by the integer number of anticrossing points (N_ACP) in reciprocal space. The dispersion curves change from hyperbolic to elliptic as the twist angle increases, leading to a controlled topological transition. The results show that the dispersion curve becomes flat at a specific angle, enabling low-loss polariton propagation. The acoustic magic angle is defined as the angle where the dispersion curve becomes flat, enabling highly directional propagation. The study also demonstrates the H2E topological transition in a tTL system, extending the frequency range of the topological transition and providing additional degrees of freedom for controlling energy conduction. Theoretical and experimental results show that the tBL system can achieve a topological transition over a wide frequency range, with the dispersion curves becoming flat at the acoustic magic angle. The study also demonstrates the H2E topological transition in a tTL system, extending the frequency range of the topological transition and providing additional degrees of freedom for controlling energy conduction. The results confirm the acoustic equivalence of the Lifshitz transition from the hyperbolic to elliptic phase. The study provides a framework for designing and understanding acoustic metasurfaces, with potential applications in various systems, including those with twisted hyperbolic metasurfaces and anisotropic acoustic impedances.
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