arXiv subjects

Guoliang Huang

Publications and source records attributed to Guoliang Huang.

At least 19 recordsLinked to original sources

arXiv2026

Wave Scattering at temporal interfaces with spatial-translation-symmetry mismatch

Temporal interfaces enable wave manipulation through broken time-translation symmetry, but conventional formulations generally assume that spatial-translation symmetry is preserved across the interface. Here we consider temporal interfaces between periodic media with mismatched spatial symmetries. It is discovered that the reciprocal-lattice vectors of the pre- and post-switching media enter a generalized quasi-momentum-matching condition, giving rise to reciprocal-lattice-assisted wave-vector conversion. We then develop a multichannel temporal-scattering theory and validate it in one- and two-dimensional elastic lattices. A single incident Bloch mode can thereby excite multiple post-interface Bloch modes with distinct wave vectors and frequencies, a response inaccessible at conventional temporal interfaces. These results establish symmetry mismatch as a new degree of freedom for simultaneous control of wave vector and frequency in time-modulated periodic media.

physics.class-ph↗

arXiv2025

A controllable anti-P-pseudo-Hermitian mechanical system and its application

A novel anti-P-pseudo-Hermitian mechanical system that integrates piezoelectric actuators and sensors with non-reciprocal coupling into mechanical beams is proposed. This configuration enables the system to exhibit programmable exceptional points (EPs), which are critical for enhancing sensitivity in sensing applications. Our theoretical analysis, supported by numerical simulations and experimental validation, demonstrates the system's capability to detect minute mass variations and identify surface cracks with high precision. This advancement not only contributes to the field of non-Hermitian physics but also paves the way for the development of next-generation mechanical sensors leveraging EP physics.

physics.app-ph↗

arXiv2025

Temporal refraction and reflection in modulated mechanical metabeams: theory and physical observation

Wave reflection and refraction at a time interface follow different conservation laws compared to conventional scattering at a spatial interface. This study presents the experimental demonstration of refraction and reflection of flexural waves across a temporal boundary in a continuum based mechanical metabeam, and unveils opportunities that emerge by tailoring temporal scattering phenomena for phononic applications. We observe these phenomena in an elastic beam attached to an array of piezoelectric patches that can vary in time the effective elastic properties of the beam. Frequency conversion and phase conjugation are observed upon a single temporal interface. These results are consistent with the temporal Snell law and Fresnel equations for temporal interfaces. Further, we illustrate the manipulation of amplitude and frequency spectra of flexural wave temporal refraction and reflection through multi stepped temporal interfaces. Finally, by implementing a smooth time variation of wave impedance, we numerically and experimentally demonstrate the capabilities of the temporal metabeam to realize waveform morphing and information coding. Our findings lay the foundation for developing time mechanical metamaterials and time phononic crystals, offering new avenues for advanced phonon manipulation in both wave amplitude and frequency

physics.optics↗

arXiv2024

A Constrained Mechanical Metamaterial Towards Wave Polarization and Steering Control

Precise control of the polarization and propagation direction of elastic waves is a fundamental challenge in elastodynamics. Achieving efficient mode conversion along arbitrary paths with conventional techniques has proven difficult. In this letter, we propose an innovative harmonimode mechanical metamaterial by integrating classical lattice architecture with a constrained mechanism. The constrained discrete mass-spring model is formulated and homogenized to reveal the unique harmonimode behavior, which supports single-mode polarized propagation and perfect impedance matching with the reference medium. Leveraging multi-scale simulations and the discrete transformation method, the metamaterial is designed to exhibit degenerated wave polarization and broadband mode conversion along various paths by simply adjusting constraint orientations. Finally, hinge joints are proposed for the physical realization of the metamaterial with sub-wavelength microstructures. Numerical simulations confirm its exceptional wave control performance over a broad frequency range. This work presents a comprehensive framework for designing harmonimode metamaterials capable of arbitrary polarization control.

physics.app-ph↗

arXiv2024

Perspective on Non-Hermitian Elastodynamics

The manipulation of mechanical waves is a long-standing challenge for scientists and engineers, as numerous devices require their control. The current forefront of research in the control of classical waves has emerged from a seemingly unrelated field, namely, non-Hermitian quantum mechanics. By drawing analogies between this theory and those of classical systems, researchers have discovered phenomena that defy conventional intuition and have exploited them to control light, sound, and elastic waves. Here, we provide a brief perspective on recent developments, challenges and intricacies that distinguish non-Hermitian elastodynamics from optics and acoustics. We close this perspective with an outlook on potential directions such as topological phases in non-Hermitian elastodynamics and broken Hermitian symmetry in materials with electromomentum couplings.

physics.class-ph↗

arXiv2024

Intelligent mechanical metamaterials towards learning static and dynamic behaviors

The exploration of intelligent machines has recently spurred the development of physical neural networks, a class of intelligent metamaterials capable of learning, whether in silico or in situ, from observed data. In this study, we introduce a back-propagation framework for lattice-based mechanical neural networks (MNNs) to achieve prescribed static and dynamic performance. This approach leverages the steady states of nodes for back-propagation, efficiently updating the learning degrees of freedom without prior knowledge of input loading. One-dimensional MNNs, trained with back-propagation in silico, can exhibit the desired behaviors on demand function as intelligent mechanical machines. The framework is then employed for the precise morphing control of the two-dimensional MNNs subjected to different static loads. Moreover, the intelligent MNNs are trained to execute classical machine learning tasks such as regression to tackle various deformation control tasks. Finally, the disordered MNNs are constructed and trained to demonstrate pre-programmed wave bandgap control ability, illustrating the versatility of the proposed approach as a platform for physical learning. Our approach presents an efficient pathway for the design of intelligent mechanical metamaterials for a wide range of static and dynamic target functionalities, positioning them as powerful engines for physical learning.

physics.app-ph↗

arXiv2024

Smart patterning for topological pumping of elastic surface waves

Topological pumping supplies a robust mechanism to steer waves across a sample without being affected by disorders and defects. For the first time, we demonstrate the pumping of elastic surface waves, achieved by a smart patterning of a surface that creates a synthetic dimension, which is explored by the wave as it is launched perpendicularly to the steering direction. Specifically, we design and fabricate an elastic medium decorated with arrays of pillar-type resonators whose eigenmodes are locate below the sound cone, together with coupling bridges edged according to a specific algorithm. We establish a connection between the collective dynamics of the pillars and that of electrons in a magnetic field by deriving an accurate tight-binding model and developing a WKB-type analysis suitable for such discrete aperiodic systems with spatially slow-varying couplings. This enable us to predict topological pumping pattern, which is numerically and experimentally demonstrated by steering waves from one edge of the system to the other. Finally, the immune character of the topologically pumped surface waves against disorder and defects is evidenced. The principle of surface patterning together with the WKB-analysis could provide a powerful new platform for surface wave control and exploration of topological matter in higher dimensions.

physics.app-ph↗

arXiv2024

Topological Spectral Bands with Frieze Groups

Frieze groups are discrete subgroups of the full group of isometries of a flat strip. We investigate here the dynamics of specific architected materials generated by acting with a frieze group on a collection of self-coupling seed resonators. We demonstrate that, under unrestricted reconfigurations of the internal structures of the seed resonators, the dynamical matrices of the materials generate the full self-adjoint sector of the stabilized group $C^\ast$-algebra of the frieze group. As a consequence, in applications where the positions, orientations and internal structures of the seed resonators are adiabatically modified, the spectral bands of the dynamical matrices carry a complete set of topological invariants that are fully accounted by the K-theory of the mentioned algebra. By resolving the generators of the K-theory, we produce the model dynamical matrices that carry the elementary topological charges, which we implement with systems of plate resonators to showcase several applications in spectral engineering. The paper is written in an expository style.

cond-mat.mtrl-sci↗

arXiv2022

Waves over a periodic progressive modulation: A python tutorial

This chapter presents a selection of theoretical and numerical tools suitable for the study of wave propagation in time-dependent media. The focus is on one-dimensional spring-mass chains whose properties are modulated in space and time in a periodic progressive fashion. The chapter is written for the uninitiated newcomer as well as for the theoretically inclined numerical empiricist. Thus, whenever possible, deployed theory is motivated and exploited numerically, and code for example simulations is written in python. The chapter begins with an introduction to Mathieu's equation and its stability analysis using the monodromy matrix; generalizations to systems with multiple degrees of freedom are then pursued. The progressive character of the modulation leads to a factorization of the monodromy matrix and provides a "discrete change of variables" otherwise only available for continuous systems. Moreover, the factorization allows to reduce the computational complexity of dispersion diagrams and of long term behaviors. Chosen simulations illustrate salient features of non-reciprocity such as strong left-right biases in the speed and power of propagated waves.

math.NA↗

arXiv2021

Realization of active metamaterials with odd micropolar elasticity

Materials made from active, living, or robotic components can display emergent properties arising from local sensing and computation. Here, we realize a freestanding active metabeam with piezoelectric elements and electronic feed-forward control that gives rise to an odd micropolar elasticity absent in energy-conserving media. The non-reciprocal odd modulus enables bending and shearing cycles that convert electrical energy into mechanical work, and vice versa. The sign of this elastic modulus is linked to a non-Hermitian topological index that determines the localization of vibrational modes to sample boundaries. At finite frequency, we can also tune the phase angle of the active modulus to produce a direction-dependent bending modulus and control non-Hermitian vibrational properties. Our continuum approach, built on symmetries and conservation laws, could be exploited to design others systems such as synthetic biofilaments and membranes with feed-forward control loops.

physics.app-ph↗

arXiv2021

Discrete Transformation Elasticity: An Approach to Design Lattice-based Polar Metamaterials

The transformation method is a powerful tool for providing the constitutive parameters of the transformed material in the new coordinates. In transformation elasticity, a general curvilinear change of coordinates transforms conventional Hooke's law into a different constitutive law in which the transformed material is not only anisotropic but also polar and chiral and no known elastic solid satisfies. However, this state-of-the-art description provides no insight as to what the underlying microstructure of this transformed material could be, the design of which is a major challenge in this field. The study aims to theoretically justify the fundamental need for the polar material by critically revisiting the discrete transformation method. The key idea is to let transformation gradient operate not only on the elastic properties but on the underlying architectures of the mechanical lattice. As an outstanding application, we leverage the proposed design paradigm to physically construct a polar lattice metamaterial for the observation of elastic carpet cloaking. Numerical simulations are then implemented to show excellent cloaking performance under different static and dynamic mechanical loads. The approach presented herein could promote and accelerate new designs of lattice topologies for transformation elasticity in particular and is able to be extended for realizing other emerging elastic properties and unlocking peculiar functions including statics and dynamics in general.

physics.app-ph↗

arXiv2020

Physical rendering of synthetic spaces for topological sound transport

Synthetic dimensions can be rendered in the physical space and this has been achieved with photonics and cold atomic gases, however, little to no work has been succeeded in acoustics because acoustic wave-guides cannot be weakly coupled in a continuous fashion. Here, we establish the theoretical principles and for the first time manufacture acoustic crystals composed of arrays of acoustic cavities strongly coupled through modulated channels to evidence one-dimensional (1D) and two-dimensional (2D) dynamic topological pumpings. In particular, the topological edge-bulkedge and corner-bulk-corner transport are physically illustrated in finite-sized acoustic structures. We delineate the generated 2D and four-dimensional (4D) quantum Hall effects by calculating first and second Chern numbers and demonstrating robustness against the geometrical imperfections. Synthetic dimensions could provide a powerful way for acoustic topological wave steering and open up a new platform to explore higher-order topological matter in dimensions four and higher.

cond-mat.mes-hall↗

arXiv2020

Channel-Coupling Fano Resonance and Acoustic Metadamping

Fano resonance featuring asymmetric spectral profiles originates from the interference of local resonances and background continuum. Its narrow-band nature looks seemingly adverse to broadband noise cancellation purposes. In this study, we report theoretically on an intriguing acoustic metamaterial capable of generating multiple Fano-like resonances to realize a broadband sound barrier with satisfactory transmission loss performance. Our proposed design involves an effective channel characterized by effective parameters and short channels filled with air. The effective channel support both monopolar and dipolar modes which interact with the continuum state admitted by the short channels to generate a pair of Fano-like resonances. Due to the destructive interference of sound waves, the two resonances result in transmission loss overall exceeding 10 dB over a broad range 0.6-1.1 kHz. In order to further optimize the overall performance, we introduce metadamping by integrating additional viscous foams in the proposed unit cell. Furthermore, for future experimental tests, the dampened design is decoded into a real space-coiling cell which exhibits identical functionality and is assembled into a partition wall to ensure transmission loss over 10 dB across the range 0.32-4 Hz. Lastly, acoustic negative refraction is accessible by deploying two coupled space-coiling channels in a similar fashion. We believe this work paves the way for realizing effective broadband sound insulation devices with efficient ventilation.

physics.app-ph↗

arXiv2020

Microtwist elasticity: A continuum approach to zero modes and topological polarization in Kagome lattices

The topologically polarized isostatic lattices discovered by Kane and Lubensky (2014, Nat. Phys. 10, 39-45) challenged the standard effective medium theories used in the modeling of many truss-based materials and metamaterials. As a matter of fact, these exhibit Parity (P) asymmetric distributions of zero modes that induce a P-asymmetric elastic behavior, both of which cannot be reproduced within Cauchy elasticity. Here, we propose a new effective medium theory baptized "microtwist elasticity" capable of rendering polarization effects on a macroscopic scale. The theory is valid for trusses on the brink of a polarized-unpolarized phase transition in which case they necessarily exhibit more periodic zero modes than they have dimensions. By mapping each periodic zero mode to a macroscopic degree of freedom, the microtwist theory ends up being a kinematically enriched theory. Microtwist elasticity is constructed thanks to leading order two-scale asymptotics and its constitutive and balance equations are derived for a fairly generic isostatic truss: the Kagome lattice. Various numerical and analytical calculations, of the shape and distribution of zero modes, of dispersion diagrams and of polarization effects, systematically show the quality of the proposed effective medium theory. Most notably, the theory is capable of producing a continuum version of Kane and Lubensky's topological polarization vector.

physics.class-ph↗

arXiv2018

Observation of nonreciprocal wave propagation in a dynamic phononic lattice

Acoustic waves in a linear time-invariant medium are generally reciprocal; however, reciprocity can break down in a time-variant system. In this Letter, we report on an experimental demonstration of nonreciprocity in a dynamic one-dimensional phononic crystal, where the local elastic properties are dependent on time. The system consists of an array of repelling magnets, and the on-site elastic potentials of the constitutive elements are modulated by an array of electromagnets. The modulation in time breaks time-reversal symmetry and opens a directional band gap in the dispersion relation. As shown by experimental and numerical results, nonreciprocal mechanical systems like the one presented here offer opportunities to create phononic diodes that can serve for rectification applications.

physics.app-ph↗

arXiv2018

Wave propagation in infinite nonlinear acoustic metamaterial beam by considering the third harmonic generation

Nonlinear acoustic metamaterial (NAM) initiates new fields for controlling elastic waves. In this work, the flexural wave propagation in the half-infinite NAM beam consisting of periodic Duffing resonators is reported by considering the third harmonic generation (THG). Different analytical methods are proposed to describe the wave propagation in the equivalent homogenous medium. Then their effectiveness and accuracy are demonstrated in comparison with the finite element methods. We unveil analytically and numerically extensive physical properties of the strongly nonlinear AM, including the nonlinear resonance in a cell, the effective density, nonlinear locally resonant (NLR) bandgap, propagations and couplings of the fundamental and the third harmonics. These characteristics are highly interrelated, which facilitates the prediction of functionalities. In the near field, the identical bifurcation frequency of these features acts as the start frequency of the NLR bandgap for fundamental waves, whose width is narrower for a stronger nonlinearity. While in the far field, the NLR bandgap characterizes a distance-amplitude-dependent behavior leading to a self-adaptive bandwidth. Moreover, the transmission in the passband of the infinite NAM is different from the chaotic band effect of finite NAMs, and it is influenced by the shifted NLR gap. Our work will promote future studies and constructions of NAMs with novel properties.

physics.app-ph↗

arXiv2018

Elastic quantum spin-Hall effect in Kagome lattices

A Quantum Spin-Hall Insulator (QSHI) is implemented into a simple mass-spring Kagome lattice. The transition from the trivial state to the topological one is described by an invariant Chern number function of a contrast parameter. The band diagram and helical edge states characteristic of QSHI are obtained by a combination of numerical and analytical methods. In particular, these states are shown to be Stoneley wave solutions to a set of asymptotic continuous motion equations. Last, scatterless propagation of polarized topological edge waves around sharp corners is demonstrated and robustness is assessed through a parametric study.

cond-mat.mes-hall↗

arXiv2018

Topological mechanics of edge waves in Kagome lattices

Topological insulators are new phases of matter whose properties are derived from a number of qualitative yet robust topological invariants rather than specific geometric features or constitutive parameters. Here, Kagome lattices are classified based on a topological invariant directly related to the handedness of a couple of elliptically polarized stationary eigenmodes in the context of what is known as the "quantum valley Hall effect" in physics literature. An interface separating two topologically distinct lattices, i.e., two lattices with different topological invariants, is then proven to host two topological Stoneley waves whose frequencies, shapes and decay and propagation velocities are quantified. Conversely, an interface separating two topologically equivalent lattices will host no Stoneley waves. Analysis is based on an asymptotic model derived through a modified high-frequency homogenization procedure. This case study constitutes the first implementation of the quantum valley Hall effect in in-plane elasticity. A preliminary discussion of 1D lattices is included to provide relevant background on topological effects in a simple analytical framework.

cond-mat.mes-hall↗