Hermitian theories play a major role in understanding the physics of most phenomena. It has been found only past decade that non-Hermiticity enables unprecedented effects such as exceptional points, spectral singularities and bulk Fermi arcs. Recent studies further show can fundamentally change topological band theory, leading to non-Hermitian topology skin effect, confirmed one-dimensional (1D) systems. However, higher dimensions, these remain unexplored experiments. Here, we demonstrate...

Auxetic metamaterials have received wide attention due to their idiosyncratic physical properties. In this paper, experiments and simulations were performed study the mechanical acoustic properties of a 3D anti-chiral auxetic metamaterial subjected quasi-static loading. The results shows that Poisson's ratio designed can be changed from −0.45 0.35 with different cell parameters. Acoustic tests show provides an ultra-wide phononic bandgap exhibits outstanding wave attenuation By applying...

Abstract The last 20 years have witnessed growing impacts of the topological concept on branches physics, including materials, electronics, photonics, and acoustics. Topology describes objects with some global invariant property under continuous deformation, which in mathematics could date back to 17th century mature 20th century. In it successfully underpinned physics Quantum Hall effect 1984. To date, topology has been extensively applied describe phases acoustic metamaterials. As...

We present an effective medium theory that can predict the permittivity and permeability of a geometrically anisotropic two-dimensional metamaterial composed with rectangular array elliptical cylinders. It is possible to obtain closed-form analytical solution for parameters if aspect ratio lattice eccentricity cylinder satisfy certain conditions. The derived recover well-known Maxwell-Garnett results in quasi-static regime. More importantly, it valid beyond long-wavelength limit, where...

The introduction of non-Hermiticity to topological systems profoundly modifies their properties, leading unprecedented phenomena beyond the descriptions Bloch band theory, e.g., breakdown conventional bulk-boundary correspondence. However, comprehensive interplay between topology and remains elusive. Here, based on a non-Hermitian Su-Schrieffer-Heeger model, we demonstrate that in systems, by competing with each other, exhibiting transition from symmetry dominance dominance. former is...

Acoustic metamaterials (AMMs) are a type of artificial materials that make use appropriate structural designs and exhibit exotic properties not found in natural materials, such as negative effective material parameters (e.g., bulk modulus, mass density, refractive index). These interesting offer novel means for sound manipulation thus have drawn great deal attention. Over the past two decades, tremendous progress has been made fundamental research AMMs, which only promoted development modern...

We present a design for an acoustic metasurface which can efficiently absorb low-frequency sound energy in water. The has simple structure and consists of only two common materials: i.e., water silicone rubber. optimized material geometrical parameters the designed are determined by analytic formula conjunction with iterative process based on retrieval method. Although is as thin 0.15 wavelength, it 99.7% normally incident wave energy. Furthermore, maintains substantially high absorptance...

Higher-order topological insulators (HOTIs) in classical systems, featuring robust multidimensional boundary states protected by various crystalline symmetries, have become a fast-growing research branch the vast family. Therein, valley pseudospins and layer are separately introduced as extra degrees of freedom (DOFs) to manipulate phases. Here, we experimentally demonstrate that, combining DOFs, intriguing HOTIs can be realized. They host edge corner that simultaneously dependent polarized....

We present the design of a tunable two-dimensional photonic crystal that exhibits multiple topological phases, including conventional insulator phase, quantum spin Hall and anomalous phase under different combinations geometric parameters external magnetic fields. Our enables platform to study topology evolution attributed interplay between crystalline symmetry time-reversal symmetry. A four-band tight-binding model unambiguously reveals property is associated with pseudospin orientations it...

Acoustic imaging techniques suffer from the diffraction limit due to loss of evanescent waves that carry subwavelength information objects. To overcome limit, components have be collected and measured. Most existing methods targeting this task rely on expensive detector arrays inefficient near-field point-by-point scanning. Here, we propose experimentally demonstrate realization a far-field acoustic method based single stationary detector. Specifically, utilize series masks structure...

Non-Hermiticity is revolutionizing the common understanding in Hermitian scope by interfacing with topological physics. A single non-Hermitian band can host nontrivial topology that defined over nonzero windings of system's eigenvalues, but not eigenvectors, as opposed to systems. This unique responsible for intriguing skin effect. Here, we show one-band models experience multiple phase transitions. Each transition identified a change eigenvalue winding. Such an interesting phenomenon...

Topological phases of matter with robust edge states have revolutionized the fundamental intuitions for wave control. The recent development higher-order topological insulators (HOTIs) realizes even lower dimensional that enable versatile manipulations (e.g., light imaging). However, in conventional HOTIs, are usually protected by certain crystalline symmetries and therefore bounded at specific locations, hindering their applications modern digital ears, which often prefer tunability...

We present a lumped model to study the rotational modes in type of two-dimensional periodic solid composites comprised square array rubber-coated steel cylinders embedded an epoxy matrix. The captures physical essence such systems for various combinations material parameters, and, therefore it is able describe transition behaviour when system gradually adjusted from elastic metamaterial phononic crystal. From model, we can define zone which separates typical metamaterials and crystals.

Abstract Hermitian theories play a major role in understanding the physics of most phenomena. It has been found only past decade that non-Hermiticity enables unprecedented effects such as exceptional points, spectral singularities and bulk Fermi arcs. Recent studies further show can fundamentally change topological band theory, leading to non-Hermitian topology skin effect, confirmed one-dimensional (1D) systems. However, higher dimensions, these remain unexplored experiments. Here, we...

We propose a unified scheme to achieve coherent perfect absorption of electromagnetic waves by anisotropic metamaterials. The describes the condition on and offers an inverse design route based effective medium theory in conjunction with retrieval method determine practical metamaterial absorbers. is scalable frequencies applicable various incident angles. Numerical simulations show that achieved designed absorbers over wide range angles, verifying scheme. By integrating these absorbers, we...

Spin and orbital angular momenta are fundamental physical characteristics described by polarization spatial degrees of freedom, respectively. Polarization is a feature vector fields while phase gradient determines the momentum ubiquitous to any scalar field. Common wisdom treats these two freedom as distinct independent principles manipulate wave propagations. Here, we demonstrate their synergy. This achieved introducing orthogonal $p$-orbitals eigenbases, whose modal features exploited...

Abstract Spin angular momentum (SAM) and orbital (OAM) are fundamental physical characteristics described by polarization spatial degrees of freedom, respectively. Polarization is a feature vector fields while phase gradient determines the OAM ubiquitous to any scalar field. Common wisdom treats these two freedom as independent principles manipulate wave propagations. Here, their synergy demonstrated. This achieved introducing orthogonal p ‐orbitals eigenbases, whose modal features exploited...