arXiv subjects

Qingxiang Ji

Publications and source records attributed to Qingxiang Ji.

7 recordsLinked to original sources

arXiv2026

Nonreciprocal topological kink-wave propagation in mechanical metamaterials

Nonlinear mechanical metamaterials can exhibit emergent transport phenomena that mimic topological protection without relying on linear band topology. Here, we realize a bifurcation-induced nonreciprocal lattice that supports robust propagation of elastic kink waves. Each unit is a prestrained, hinged-beam circulator that develops angular momentum bias during snap-through transitions between buckling states, producing an effective breaking of time reversal symmetry. Coupling such units into a hexagonal array yields a mechanically chiral network where localized soliton-like excitations propagate unidirectionally along interfaces and edges, immune to sharp bends. We demonstrate non-dispersive kink transport governed by a SineGordon type field whose effective bias encodes mechanical chirality. This framework bridges bifurcation dynamics and nonreciprocal transport, establishing a nonlinear route toward topological like mechanical functionality without magnetic or gyroscopic bias.

cond-mat.mtrl-sci↗

arXiv2025

Controlling the Propagation of Flexural Elastic Waves With Ceramic Metatiles

In this work, we examine the application of phononic metamaterials for elastic impact noise insulation in tiled flooring, through the development of an innovative ceramic metatile that incorporates phononic crystals with optimized joint configurations. First, we optimize the geometrical and material parameters of the proposed metatile, which is composed of small ceramic subtiles connected by silicon joints, in order to reduce longitudinal and flexural wave propagation on tiled floors, which are responsible for noise vibrations in tiled environments. A bandgap is achieved that effectively suppresses the transmission of impact noise through the periodic structural configuration. For flexural waves, the ceramic metatile exhibits a pronounced attenuation of wave transmission in the range of $500$-$1900$ Hz along the $[100]$ direction, and $500$-$1400$ Hz along the $[110]$ direction. For longitudinal waves, a broad bandgap is observed, spanning from $400$ Hz to $1950$ Hz in both the $[100]$ and $[110]$ directions. Additionally, the bandgaps shift toward lower frequencies with increasing width of the subtiles and silicon joints, or with a decrease in the Young's modulus of the silicon. In both experimental and numerical tests, it is demonstrated that the integration of silicon joints inside the ceramic metatile improves the acoustic insulation performance, as measured by the reduction of impact noise levels across a wide range of low frequencies. The findings highlight the potential of metamaterials in architectural acoustics, offering innovative solutions for elastic wave control in tiled environments.

physics.app-ph↗

arXiv2025

On the Practicability of Ceramic-Tiled Walls for Sound Absorption by Tuning Cavities

We present the practicality of structuring ceramic tiles for enhancing sound absorption on rigid walls. The cornerstone of our methodology is to structure walls with cavities so that walls effectively behave as heterogeneous absorbing surfaces over a large frequency bandwidth. Using this approach, ceramic tiled walls are developed by integrating tuned cavity structures based on Helmholtz resonators. Such a design leverages the empty joints between tiles to form resonator necks, while the space between the ceramic tiles and the wall acts as the resonator chambers. By arranging these resonators in a spatially graded array, we achieve broadband sound absorption which targets low-frequency noise generated by impacts, footsteps and ambient sources. This makes the system highly suitable for practical architectural applications. The study encompasses the entire process, from numerical modeling and analytical formulation to the fabrication and mounting of resonant tiles, followed by experimental validation, clearly demonstrating the effectiveness of the proposed solution in real-world conditions. The findings highlight the strong potential of this approach for practical tiled room acoustic treatment and noise mitigation.

physics.app-ph↗

arXiv2025

Space-Time Elastic Metamaterials for Zero-Frequency and Zero-Wavenumber Bandgaps

We create wave-matter space-time metamaterials using optical trapping forces to manipulate mass-spring chains and create zero-frequency and zero-wavenumber band gaps: the bosonic nature of phonons, and hence this elastodynamic setting, traditionally prohibits either zero-frequency or zero-wavenumber band gaps. Here, we generate zero-frequency gaps using optomechanical interactions within a 3D mass-spring chain by applying an optical trapping force to hold or manipulate a mass in a contactless manner independent of its elastodynamic excitations. Through careful modification of the geometrical parameters in the trapped monoatomic mass-spring chain, we demonstrate the existence of a zero-frequency gap generated by the optical forces on the masses. The precise control we have over the system allows us to drive another set of masses and springs out of phase with its traveling wave thereby creating a zero-wavenumber band gap.

physics.optics↗

arXiv2024

Unconventional superconductivity in magic-strain graphene superlattices

Extensive investigations on the Moiré magic-angle have been conducted in twisted bilayer graphene, unlocking the mystery of unconventional superconductivity and insulating states. In analog to magic angle, here we demonstrate the new concept of magic-strain in graphene systems by judiciously tailoring mechanical relaxation (stretch and compression) which is easier to implement in practice. We elucidate the interplay of strain-induced effects and delve into the resulting unconventional superconductivity or semimetal-insulator transition in relaxation-strained graphene, going beyond the traditional twisting approach. Our findings reveal how relaxation strain can trigger superconducting transitions (with an ultra-flat band at the Fermi level) or the semimetal-insulator transition (with a gap opening at the $K$ point of $0.39\rm{~eV}$) in both monolayer and bilayer graphene. These discoveries open up a new branch for correlated phenomena and provide deeper insights into the underlying physics of superconductors, which positions graphene as a highly tunable platform for novel electronic applications.

cond-mat.mes-hall↗

arXiv2020

Designing thermal energy harvesting devices with natural materials through optimized microstructures

Metamaterial thermal energy devices obtained from transformation optics have recently attracted wide attention due to their vast potential in energy storage, thermal harvesting or heat manipulation. However, these devices usually require inhomogeneous and extreme material parameters which are difficult to realize in large-scale applications. Here, we demonstrate a general process to design thermal harvesting devices with available natural materials through optimized composite microstructures. We apply two-scale homogenization theory to obtain effective properties of the microstructures. Optimal Latin hypercube technique, combined with a genetic algorithm, is then implemented on the microstructures to achieve optimized design parameters. The optimized microstructures can accurately approximate the behavior of transformed materials. We design such devices and numerically characterize good thermal-energy harvesting performances. To validate the wide-range application of our approach, we illustrate other types of microstructures that mimic well the constitutive parameters. The approach we propose can be used to design novel thermal harvesting devices available with existing technology, and can also act as a beneficial vehicle to explore other transformation optics enabled designs.

physics.app-ph↗

arXiv2020

Optimal isotropic, reusable truss lattice material with near-zero Poisson's ratio

Cork is a natural amorphous material with near-zero Poisson's ratio that is ubiquitously used for sealing glass bottles. It is an anisotropic, transversally isotropic, composite that can hardly be scaled down. Here, we propose a new class of isotropic and reusable cork-like metamaterial that is designed from an hybrid truss-lattice material to show an isotropic Poisson's ratio close to zero. Optimization is conducted using a multi-objective genetic algorithm, assisted by an elliptical basis function neural network, and coupled with finite element simulations. The optimal micro-structured metamaterial, fabricated by two-photon lithography with a lattice constant of 300 \micro\meter, has an almost isotropic Poisson's ratio smaller than 0.08 in all directions. It can recover $96.6\%$ of its original shape after a compressional test exceeding $20\%$ strain.

physics.app-ph↗