Topological transition in spiral elastic valley metamaterials

Valley Anisotropy in Elastic Metamaterials

Valley, as a new degree of freedom, raises the valleytronics in fundamental and applied science. The elastic analogs of valley states have been proposed by mimicking the symmetrical structure of either two-dimensional materials or photonic valley crystals. However, the asymmetrical valley construction remains unfulfilled. Here, we present the valley anisotropy by introducing asymmetrical design into elastic metamaterials. The elastic valley metamaterials are composed of bio-inspired hard spirals and soft materials. The anisotropic topological nature of valley is verified by asymmetrical distri…

Optical Valley Hall Effect of 2D Excitons in Hyperbolic Metamaterial

The robust spin and momentum valley locking of electrons in two-dimensional semiconductors make the valley degree of freedom of great utility for functional optoelectronic devices. Owing to the difference in optical selection rules for the different valleys, these valley electrons can be addressed optically. The electrons and excitons in these materials exhibit valley Hall effect, where the carriers from specific valleys are directed to different directions under electrical or thermal bias. Here we report the optical valley Hall effect where the light emission from the valley polarized exciton…

Structure-Composition Correspondence in Crystalline Metamaterials for Acoustic Valley-Hall Effect and Unidirectional Sound Guiding

Recently, the domain of topological insulators in condensed matter physics has been teeming with intriguing and very exciting discoveries. Notably, the capacity of guiding currents towards specific directions according to the spin of the travelling electrons has a great potential for electronic devices. This new phenomenon has been transposed to the classical domain in electromagnetics and acoustics, unveiling the pseudo-spin locking of guided waves. However, these macroscopic analogues are photonic/phononic crystals which are intrinsically wavelength scaled. In this work, we realize a genuine…

Topological chiral edge states in deep-subwavelength valley photonic metamaterials

Topological valley photonics has emerged as a new frontier in photonics with many promising applications. Previous valley boundary transport relies on kink states at internal boundaries between two topologically distinct domains. However, recent studies have revealed a novel class of topological chiral edge states (CESs) at external boundaries of valley materials, which have remained elusive in photonics. Here, we propose and experimentally demonstrate the topological CESs in valley photonic metamaterials (VPMMs) by accurately tuning on-site edge potentials. Moreover, the VPMMs work at deep-su…

Enhancement of deep-subwavelength band gaps in flat spiral-based phononic metasurfaces using the trampoline phenomena

Elastic and acoustic metamaterials can sculpt dispersion of waves through resonances. In turn, resonances can give rise to negative effective properties, usually localized around the resonance frequencies, which support band gaps at subwavelength frequencies (i.e., below the Bragg-scattering limit). However, the band gaps width correlates strongly with the resonators' mass and volume, which limits their functionality in applications. Trampoline phenomena have been numerically and experimentally shown to broaden the operational frequency ranges of two-dimensional, pillar-based metamaterials thr…

利用曲率在螺旋基元材料结构中产生螺旋波

Harnessing curvature for helical wave generation in spiral-based metamaterial structures

本文提出利用螺旋基元材料结构产生螺旋波，通过曲率保护的拓扑态实现无反向散射传播，无需波导或域界面，单源激发即可实现波的调控。