Lattice Array Research Articles

High-Order Topological Pumping on a Superconducting Quantum Processor.

High-order topological phases of matter refer to the systems of n-dimensional bulk with the topology of m-th order, exhibiting (n-m)-dimensional boundary modes and can be characterized by topological pumping. Here, we experimentally demonstrate two types of second-order topological pumps, forming four 0-dimensional corner localized states on a 4×4 square lattice array of 16 superconducting qubits. The initial ground state of the system at half-filling, as a product of four identical entangled 4-qubit states, is prepared using an adiabatic scheme. During the pumping procedure, we adiabatically modulate the superlattice Bose-Hubbard Hamiltonian by precisely controlling both the hopping strengths and on-site potentials. At the half pumping period, the system evolves to a corner-localized state in a quadrupole configuration. The robustness of the second-order topological pump is also investigated by introducing different on-site disorder. Our Letter studies the topological properties of high-order topological phases from the dynamical transport picture using superconducting qubits, which would inspire further research on high-order topological phases.

Second-Order Nonlinear Circular Dichroism in Square Lattice Array of Germanium Nanohelices.

Second-harmonic generation (SHG) is prohibited in centrosymmetric crystals such as silicon or germanium due to the presence of inversion symmetry. However, the structuring of such materials makes it possible to break the inversion symmetry, thus achieving generation of second-harmonic. Moreover, various symmetry properties of the resulting structure, such as chirality, also influence the SHG. In this work, we investigate second-harmonic generation from an array of nanohelices made of germanium. The intensity of the second-harmonic displayed a remarkable enhancement of over 100 times compared to a nonstructured Ge thin film, revealing the influence of interaction between nanohelices. In particular, nonlinear circular dichroism, characterized through the SHG anisotropy factor g SHG-CD, changed its sign not only with the helix handedness but also with its density as well. We believe that our discoveries will open up new paths for the development of nonlinear photonics based on metamaterials and metasurfaces made of centrosymmetric materials.

Mitigation effects of lattice structure arrays on heat transfer deterioration of supercritical CO2

This study numerically investigates the suppression mechanism of heat transfer deterioration (HTD) of supercritical carbon dioxide (SCO2) in heated vertical channels with lattice structure arrays (LSA). The influences of lattice structure parameters on the velocity field, temperature field, heat transfer coefficient, buoyancy effect and flow acceleration effect are analyzed. The results demonstrate that compared to smooth channels, the tri-claw LSA can significantly reduce the maximum peak wall temperature by up to 57 K. The heat transfer coefficient substantially increases, and the fluid turbulent kinetic energy (TKE) quintuples. The vortex structures generated by lattice structures can enhance turbulence intensity and heat transfer, which effectively mitigates buoyancy effect and ultimately suppresses HTD. Increasing the lattice claws number can create more complex vortex structures, lengthening the lattice disrupts the laminar flow within the boundary layer, increasing the lattice diameter can produce a composite vortex that enhances the strength of flow mixing. An increase lattice number across the cross-section strengthens the suppression effect, but an excessive number may lead to instability. A dense lattice arrangement can continually suppress HTD, achieving an overall improvement in heat transfer within a certain range. This paper could support the design of heat exchangers in SCO2 Brayton cycles.

Design and mechanical performance analysis of T-BCC lattice structures

The Body-Centered Cubic (BCC) lattice structure is commonly used in high-end equipment fields, such as aerospace, due to its superior mechanical properties, lightweight characteristics, and ease of processing. However, there is a need to improve the performance-to-weight ratio of the traditional BCC lattice structure. This study utilizes topology optimization to design a T-BCC lattice structure based on the BCC unit cell, with the aim of maximizing stiffness. A model proposing the characterization of the Young's modulus of BCC lattice structures is presented. The model is based on calculations of cell porosity and beam stress analysis, assuming a large cell. This approach indirectly enables the calculation of the Young's modulus of T-BCC lattice arrays in multiple dimensions. Simulation and experimental comparison were used to analyze the compressive performance and load-bearing modes of T-BCC lattice structures, revealing the mechanisms of compressive deformation and failure modes. The accuracy of the characterization model for Young's modulus was found to be 93.1%. Compared to BCC lattice structures designed by traditional methods, T-BCC lattice structures designed via topology optimization can increase the Young's modulus by up to 36% and yield strength by 37.2%. This suggests that T-BCC lattice structures are a more lightweight and efficient solution for designing components in high-end equipment fields.

Numerical study on heat transfer deterioration of supercritical CO2 in lattice structure array channel

This study numerically explores the fluid flow and heat transfer features of supercritical carbon dioxide (CO2) in lattice structure array channel. The mitigation mechanism of the miniature cylindrical lattice structure array on heat transfer deterioration (HTD) of supercritical CO2 in vertically upward heated channel is studied. This paper evaluates the effect of several key influential parameters (length, diameter, pitch and number) of cylindrical lattice structure array on fluid flow field involving vortex structures, heat transfer coefficient, buoyancy effect and accelerated effect. The results indicate that the lattice structure can effectively suppress the HTD by generating the vortex structure which promoting the turbulent mixing effect and enhancing the turbulent kinetic energy (TKE) of the fluid. Compared with the smooth channel, the peak wall temperature of the lattice structure channel is reduced by about 50 °C, with a corresponding increase in the heat transfer coefficient of about 140 %. The average heat transfer coefficient of the channel is increased by more than 1/3. Furthermore, by increasing lattice length can reduce flow layer stratification and by increasing lattice diameter can creating a composite vortex, which enhance flow mixing strength. The larger the lattice pitch, the worse the overall suppression effect. A denser lattice arrangement produces more temperature valleys, thereby increasing the heat transfer coefficient. The conclusions in this study could provide the main theory support for security and stability of supercritical CO2 heat exchangers in power system.

Lagrangian dynamics of multiscale vortices in electromagnetically driven two-dimensional turbulence

We experimentally investigate the dynamics of decomposed multiscale vortex cores (VCs) as singular objects of the two-dimensional (2D) turbulence driven by the Lorentz force from a direct current electric field and 2D magnetic lattice array. It is found that, in the xyt space, VCs of each mode (i.e., vortex spatial scale) appear as a zoo of unstable wiggling filament arrays with spatially alternating signs of vorticities. VC interaction and the chaotic external Lorentz force for vorticity injection and retraction lead to: (a) the spatial bunching of the VCs of adjacent modes, and the decaying position correlation of VCs with their separation and increasing mode number; (b) single VC dissociation and VC pair recombination, and in turn stretched exponential distributions of VC lifetimes of all modes; (c) similar persistent (super) diffusions of VCs of all modes, associated with persistent changes of the mean square vorticity fluctuations of VCs of the corresponding modes; and (d) the positively correlated instantaneous energy (enstrophy) variations between two neighboring VCs of modes 3 (the scale of the magnetic array for external vorticity injection and retraction) and its harmonics mode 4, and two-way instantaneous energy (enstrophy) exchange of the flow field surrounding VCs of modes 1–2 and modes 2–3.

Multiresonant all-dielectric metasurfaces based on high-order multipole coupling in the visible.

In many cases, optical metasurfaces are studied in the single-resonant regime. However, a multiresonant behavior can enable multiband devices with reduced footprint, and is desired for applications such as display pixels, multispectral imaging and sensing. Multiresonances are typically achieved by engineering the array lattice (e.g., to obtain several surface lattice resonances), or by adopting a unit cell hosting one (or more than one) nanostructure with some optimized geometry to support multiple resonances. Here, we present a study on how to achieve multiresonant metasurfaces in the visible spectral range by exploiting high-order multipoles in dielectric (e.g., diamond or titanium dioxide) nanostructures. We show that in a simple metasurface (for a fixed particle and lattice geometry) one can achieve triple resonance occurring nearly at RGB (red, green, and blue) wavelengths. Based on analytical and numerical analysis, we demonstrate that the physical mechanism enabling the multiresonance behavior is the lattice induced coupling (energy exchange) between high-order Mie-type multipoles moments of the metasurface's particles. We discuss the influence on the resonances of the metasurface's finite size, surrounding material, polarization, and lattice shape, and suggest control strategies to enable the optical tunability of these resonances.

Numerical simulation of liquid water transport in ordered microstructures gas diffusion layer of proton exchange membrane fuel cell

The performance of the gas diffusion layer (GDL) plays a pivotal role in ensuring the efficient and stable operation of proton exchange membrane fuel cells (PEMFCs). Microstructure of the GDL significantly influences its internal water transport capabilities. In this article, the lattice array method is employed to construct ordered microstructures within GDLs, followed by the utilization of phase field method to numerically simulate water transport among these structures. The effects of lattice edge length, lattice height, and lattice shape on water transport throughout the GDL are investigated. The results reveal that excessively large or small lattice edge lengths detrimentally affect effective water transport within the GDL. Additionally, a smaller lattice height can accelerate the breakthrough of liquid water through the GDL. Notably, when the lattice height is smaller than the lattice edge length, it enhances the mass transfer. Moreover, the triangular lattice impedes the water flow, while the rectangular structure diminishes the transmission efficiency of liquid water. In contrast, hexagonal and octagonal structures exhibit the ability to alleviate the transport resistance of liquid water, with the octagonal lattice demonstrating superior mass transfer effectiveness. These findings underscore the paramount importance of meticulous structural design in further augmenting the mass transfer performance of ordered GDLs. The research provides meaningful guidance for the design of GDL structures.

Enhanced Fiber Long‐Range Surface Plasmon Sensing Enabled by Resonance Coupling to Surface Plasmon Polaritons

A tunable fiber optic (FO) long‐range surface plasmon (LRSP) sensor with strong coupling is developed and demonstrated theoretically in this article. The sensor consists of a square lattice array of Ag nanodisks resting on the FO end face. Utilizing nanodisks with small diameters leads to the pronounced excitation of two distinct and independent resonant modes: surface plasmon polaritons (SPP) and LRSP. A systematic investigation is performed to evaluate the sensing performance and capabilities of the sensor, focusing on its bulk and surface sensitivity. Significantly, the LRSP mode demonstrates high sensitivity and favorable linearity in response to refractive index (RI) changes, with an exceptionally high figure of merit (FOM). On the contrary, the SPP mode is regarded as an ideal self‐referencing mode due to its immunity to RI fluctuations. The enlargement of nanodisks diameters results in a swift redshift in the LRSP wavelength, leading to a strong coupling with the SPP mode. This coupling facilitates the transfer of electric fields within the SPP mode, promotes sensing capabilities, and enables the realization of dual‐channel sensing functionality. The occurrence of strong coupling phenomena along with the use of FO substrates provides an innovative option for achieving multifunctionality and miniaturization in sensor platforms.

Mechanism of low-voltage electrostatic fields on the water-holding capacity in frozen beef steak: Insights from myofilament lattice arrays.

This study investigated the impact of low-voltage electrostatic field-assisted freezing on the water-holding capacity of beef steaks. The enhances mechanism of water-holding capacity by electrostatic field was elucidated through the detection of dynamic changes in the myofilament lattice and the construction of an in vitro myosin filaments model. The findings demonstrated that the disorder of the myofilament array, resulted from the aggregation of myosin filaments during freezing, is a crucial factor responsible for the water loss. The intervention of the electrostatic field can effectively reduce the myofibril density by 18.7%, while maintaining a regular lattice array by modulating electrostatic and hydrophobic interactions between myofibrils. Moreover, the electrostatic field significantly inhibited the migration of immobilized water to free water, thus resulting in an increase in the water-holding capacity of myofibrils by 36%. This work provides insights into the underlying mechanisms of water loss in frozen steaks and its regulation.

Direct Numerical Simulation of Heat Transfer in a 7-Pin Wire-Wrapped Rod Bundle

The Sodium-Cooled Fast Reactor (SFR) is a promising concept chosen in the Generation IV International Forum as a possible design for pursuing the sustainable use of nuclear energy. Its core consists of multiple hydraulically isolated assemblies, with a tightly packed triangular lattice array of fuel pins enclosed in a hexagonal duct present within each assembly. Helical wire spacers are wrapped along the axis of the rods to maintain a gap between them, inducing a secondary flow, increasing the channel mixing, and enhancing convective heat transfer. In this study, a direct numerical simulation campaign is conducted for a simplified 7-pin wire wrapper geometry, with Reynolds numbers ranging from Re = 1000 to 10 000 and a Prandtl number of Pr = 0.005, to investigate heat transfer in low-flow conditions. The wire wrapper case is compared to a bare bundle case with seven pins. The results are discussed, and heat transfer predictions are compared between our numerical results and classic correlations. An anisotropy invariant map is obtained for the above-mentioned cases, and turbulent kinetic energy and turbulent heat flux budgets are computed and analyzed. Our findings provide unique insights into the flow behavior within a wire-wrapped bundle.

Spiral dynamics in oscillatory bilayer systems with an inhomogeneous inter-layer coupling

Spiral dynamics in the oscillatory bilayer system with an inhomogeneous inter-layer coupling and a spiral-resting initial state are studied, where the square coupled patches are arranged into a square lattice array. Depending on the patch side length, the lattice space and the coupling strength, different dynamical behaviors can be observed. The complete synchronization of two spiral waves easily occurs when the coupled areas occupy a larger proportion in the whole region. The bilayer system can also show several typical asynchronous patterns, where the spiral with the closed tip path, the spiral with the complex phase shifting, the state with multiple spirals, the spiral turbulence, and the non-smooth traveling pulses can be formed in the single layers of the bilayer. The variable difference functions are computed, and three types of asymptotic behaviors are identified, which include the behaviors of approaching the constant, periodic variation, and aperiodic variation around the constant. These asymptotic behaviors can describe some properties of the bilayer patterns after a transient interval. For example, the variable difference function has a periodical asymptotic behavior when the spiral with the closed tip path is formed in the single layer. The heterogeneity of inter-layer coupling can also induce some complex tip trajectories.

Artificial Magnetic Tripod Ice.

We study the collective behavior of interacting arrays of nanomagnetic tripods. These objects have six discrete moment states, in contrast to the usual two states of an Ising-like moment. Our experimental data demonstrate that triangular lattice arrays form a "tripod ice" that exhibits charge ordering among the effective vertex magnetic charges, in direct analogy to artificial kagome spin ice. The results indicate that the interacting tripods have effective moments that act as emergent local variables, with strong connections to the well-studied Potts and clock models. In addition, the tripod moments display a tendency toward a nearest neighbor alignment in our thermalized samples that separates this system from kagome spin ice. Our results open a path toward the study of the collective behavior of nonbinary moments that is unavailable in other physical systems.

Crashworthiness design of functional gradient bionic structures under axial impact loading

Gradient structures have become a hot research topic because of their excellent crashworthiness. Inspired by the gradient distribution of human bone and the excellent energy absorption properties of thin-walled constructions, a novel biologically inspired functionally graded lattice-filled tube (FGLT) is proposed in this paper by combining a radial gradient lattice with a thin-walled structure. Lattice arrays with different gradient patterns were prepared by laser melting (SLM) technique and embedded in square thin-walled tubes for experimental crashworthiness study. It was found that there was a 25.47% increase in specific absorption energy of uniform lattice-filled tubes with respect to empty tubes, and a 36.65% increase in specific absorption energy of graded grating filled tubes with respect to empty tubes. It is noteworthy that the peak load of the structure is only improved by 3.95% compared to the empty tube for the gradient lattice as a filler embedded in the thin-walled tube. Finally, based on the response surface methodology (RSM) and the second-generation non-dominated ranking genetic algorithm (NSGA-II), the multi-objective optimization of the new bionic gradient structure with the maximum specific energy absorption and the minimum peak load is performed. The expression of the maximum standardized impact force is obtained by dimensionless processing, which can fully explore the influence of the structural parameters on the impact load. The functional gradient bionic structure provides new ideas for the design of more effective energy absorption structures and collision avoidance systems.

Entanglement in the quantum phases of an unfrustrated Rydberg atom array

Recent experimental advances have stimulated interest in the use of large, two-dimensional arrays of Rydberg atoms as a platform for quantum information processing and to study exotic many-body quantum states. However, the native long-range interactions between the atoms complicate experimental analysis and precise theoretical understanding of these systems. Here we use new tensor network algorithms capable of including all long-range interactions to study the ground state phase diagram of Rydberg atoms in a geometrically unfrustrated square lattice array. We find a greatly altered phase diagram from earlier numerical and experimental studies, revealed by studying the phases on the bulk lattice and their analogs in experiment-sized finite arrays. We further describe a previously unknown region with a nematic phase stabilized by short-range entanglement and an order from disorder mechanism. Broadly our results yield a conceptual guide for future experiments, while our techniques provide a blueprint for converging numerical studies in other lattices.

Theoretical simulated fabrication of nanostructure by interference of four-beam guided mode excited by 193 nm laser

This study proposed a lithography method for fabricating periodic nanostructures using the interference of four-beam TE0 guided modes excited by a 193 nm deep ultraviolet laser. The physical mechanism and normalized electric field intensity distribution of four-beam TE0 guided mode interference were theoretically analyzed and numerically simulated using the finite element method. The simulation results confirmed the ability of this method to fabricate periodic structures with a half-pitch resolution of 30.35 nm (approximately λ/6.36), an aspect ratio of 3.95, and a contrast ratio of 1. The theoretically calculated value of the resolution was consistent with the numerical simulation value. The resolution and aspect ratio of the fabricated nanostructures could be adjusted through changes to the thickness of the resist. Moreover, the shape of the fabricated nanostructures, such as the one-dimensional sub-wavelength grating structure and two-dimensional square array lattice structure, were adjustable via changes to the number and azimuth of the excited TE0 guided modes. The results obtained in this study provide valuable theoretical information for the practical manufacture of ultra-high-resolution lithography.

Enhancing plane-wave emission with a combination device based on acoustic metamaterial

Generating high sound-intensity plane waves typically requires transducer arrays with complex synchronizing systems and high-output amplifiers. This work proposes a simple combination device to convert fan-shaped waves into elevated sound-pressure plane waves. The proposed device primarily relies on phase reconstruction of near-zero index metamaterials and the superposition of reflected waves in the reverberation field. The compact device, which is easy to manufacture, consists of a short waveguide equipped with two types of converters. One of the converters makes use of inverted cone's sound-guiding properties to convert fan-shaped waves into cylindrical waves over a broad frequency band. The other converter is comprised of rigid cylinders with triangular lattice arrays, effectively acting as the near-zero index metamaterial to transform cylindrical waves into plane waves. Both the simulated and experimental results show that the emitted plane waves can be linearly amplified by increasing the number of point sources that are separated by integer multiples of the wavelength in the vertical cavity. This study presents a straightforward and efficient approach to generate plane waves with a low-cost array assembly design, thereby enabling the widespread use of acoustic testing and underwater detection.

Rapid reconstruction algorithm for multifocal structured illumination microscopy

Multifocal structured illumination microscopy (MSIM) could surpass the diffraction limit by illuminating the sample with multiple-spot grid patterns. Developed as a parallel version of image scanning microscopy (ISM) to enhance data acquisition speed, MSIM can also be viewed as a variation of structured illumination microscopy (SIM) in which the conventional sinusoidal illumination is substituted with a lattice array of spots. This method outperforms regular SIM when imaging samples that are thick or highly scattered. In this study, we present a rapid reconstruction algorithm for MSIM in the spatial domain and demonstrate that the radius of its equivalent optical transfer function (OTF) support is twice that of a general wide-field microscopy in the epi-illumination geometry. Numerical simulations and experimental results have validated the effectiveness of the proposed algorithm.

Collectively Enhanced Giant Circular Dichroism of Germanium Nanohelix Square Lattice Arrays

Circular dichroism is a unique chiroptical signature of the chirality of a system and is a prevalent way to characterize and distinguish systems on a fundamental level and for their technological applicability. Thus, engineering and maximizing the chiroptical response of a single chiral object or a metasurface composed of chiral entities is a formidable task. Current efforts strongly focus on individual metallic nanostructures and their periodic ensembles to harvest on (resonant) plasmonic properties and interactions. This route, however, waives the advantages of high‐refractive‐index nanoscale materials embracing low dissipative losses at optical wavelengths and electromagnetic fields penetrating and propagating in such materials. Herein, a strong circular dichroism is demonstrated in square lattices of nanohelices made of the high‐refractive‐index semiconductor germanium, with dissymmetry factors outperforming metal‐based ensembles. The observation of a much higher dissymmetry emerges for illumination with spatially coherent light, in comparison to spatially incoherent light. High dissymmetry is attributed to cooperative coupling between single helices, resulting from the combination of dielectric resonances of both the individual helical building blocks and the highly ordered lattice.

Design of Photonic Crystal Biosensors for Cancer Cell Detection.

A photonic crystal biosensor is a compact device fabricated from photonic crystal materials, which enables the detection and monitoring of the presence and concentration changes of biological molecules or chemical substances. In this paper, we propose a biosensor for cancer cell detection based on a silicon photonic crystal with a hexagonal resonant cavity introduced in a triangular lattice array. One of the bandgap ranges of this structure is 1188 nm≤λ≤1968 nm. When the incident light wavelength is within the range of 1188 nm≤λ≤1968 nm, the transmission coefficient of this structure at the resonant wavelength of 1469.58 nm is found to reach 99.62% through the finite difference time domain method, with a quality factor of 980. Subsequently, a biosensor is designed from this structure, with its sensing mechanism relying on the change in refractive index leading to a shift in the resonant wavelength. The target sample can be identified by observing the shift in the resonant wavelength. As cancer cells and normal cells possess different refractive indices, this biosensor can be used for their detection. The maximum sensitivity of the sensor is 915.75 nm/RIU and the minimum detection limit is 0.000236 RIU.