Exciton-polariton dynamics in multilayered materials.

A transient heat transfer model for the composite multilayer insulation material structure of low-temperature liquid hydrogen storage tanks was established. The heat transfer process was analyzed, and the influences of key parameters, such as thermal boundary temperature, foam material thickness, and the number of layers in multilayer material wrappings, on the heat transfer rate of the tank were studied. It was found that the external temperature primarily achieves heat transfer through radiation, and the high thermal resistance of the multilayer material structure effectively inhibits heat transfer. Additionally, the rise in thermal boundary temperature will cause the temperature of each nodal layer in the region near the thermal boundary to increase. The thermal resistance inside the multilayer insulation material becomes greater, making heat transfer more difficult. As the thermal boundary temperature increases, the overall heat transfer rate shows an upward trend, with heat transfer through radiation increasing. An increase in the thickness of the foam material and the number of layers in the multilayer material will reduce the heat transfer rate. However, when increased to a certain extent, the contribution of the overall composite material structure to the total thermal resistance will instead decrease.

This paper presents a new method to analyze the discontinuity of a multilayer dielectric material. The multilayer material sample is loaded in an X-band rectangular waveguide and its two port S-parameters are simulated as a function of frequency using the software Ansoft HFSS. Also, by applying the mode matching technique, expressions for the S-parameters of the multilayer dielectric material as a function of complex permittivity of individual layers are developed. A single layer material formed by using materials such as Teflon, a number of two layer materials formed by combinations of plexiglass and Teflon and sample of three layer materials are also presented.

We present the first investigation of unusual nonlinear Hall effects in twisted multilayer 2D materials. Contrary to expectations, our study shows that these nonlinear effects are not merely extensions of their monolayer counterparts. Instead, we find that stacking order and pairwise interactions between neighboring layers, mediated by Berry curvatures, play a pivotal role in shaping their collective nonlinear optical response. By combining large-scale Real-Time Time-Dependent Density Functional Theory (RT-TDDFT) simulations with model Hamiltonian analyses, we demonstrate a remarkable second-harmonic transverse response in hexagonal boron nitride four-layers, even in cases where the total Berry curvature cancels out. Furthermore, our symmetry analysis of the layered structures provides a simplified framework for predicting nonlinear responses in multilayer materials in general. Our investigation challenges the prevailing understanding of nonlinear optical responses in layered materials and opens new avenues for the design and development of advanced materials with tailored optical properties.

An efficient method for rendering semi-transparent, multi-layered materials is presented. This method achieves the look of a volumetric material by exploiting several perceptual cues, based on depth and illumination, while combining multiple material layers on the surface of an otherwise non-volumetric, multi-textured surface such as the human heart shown in Figure 1. Multiple implementation strategies are suggested that allow for different trade-offs to be made between visual quality and runtime performance.

Introducing porous material into optical cavities is a critical step toward the utilization of quantum-electrodynamical (QED) effects for advanced technologies, e.g. in the context of sensing. We demonstrate that crystalline, porous metal–organic frameworks (MOFs) are well suited for the fabrication of optical cavities. In going beyond functionalities offered by other materials, they allow for the reversible loading and release of guest species into and out of optical resonators. For an all-metal mirror-based Fabry–Perot cavity we yield strong coupling (∼21% Rabi splitting). This value is remarkably large, considering that the high porosity of the framework reduces the density of optically active moieties relative to the corresponding bulk structure by ∼60%. Such a strong response of a porous chromophoric scaffold could only be realized by employing silicon-phthalocyanine (SiPc) dyes designed to undergo strong J-aggregation when assembled into a MOF. Integration of the SiPc MOF as active component into the optical microcavity was realized by employing a layer-by-layer method. The new functionality opens up the possibility to reversibly and continuously tune QED devices and to use them as optical sensors.

Porous materials provide sound absorption and noise control in various applications. In many scenarios, different porous materials may be combined into multilayer absorbers to enhance the absorptive properties. We apply the Bayesian inference framework to analyze such multilayer porous materials, developing a method to determine simultaneously the number of constituent layers as well as the physical properties of each layer in a multilayer porous material. The model-based analysis combines a measurement of the acoustic surface impedance or absorption coefficient of a potentially multilayered material sample with a transfer-matrix formulation of multilayer porous material acoustic propagation models. For each sample to be analyzed, the number of layers considered in the propagation model is varied, and Bayesian evidence is computed for each case. Selecting the model with the highest evidence parsimoniously determines the number of layers present in the sample. Once the number of layers has been determined, Bayesian parameter estimation inversely determines the physical properties of each layer by estimating the input parameters of the multilayer propagation model. The proposed method automatically determines the number of layers and physical parameters of a multilayer material without any a priori knowledge of these values.

Frequency Selective Surfaces/Volumes (FSS/Vs), periodic structures with frequency selective properties, have widely been used for millimeter and microwave applications. Some applications include filters (band pass, band stop), reflectors, radoms etc. FSS/Vs typically consist of a single or multiple material layers. Multiple layers (with each layer having a different frequency selectivity) are used for broadband applications. In recent years there has been an interest in using these structures at optical wavelengths. One of the applications is in thermophotovoltaic filters used to convert thermal energy into electricity. The filter is designed to transmit those wavelengths that can be efficiently converted into electricity, and to reflect other spectra, which leads to energy conservation and an increase in overall system efficiency. These filters can be used in space missions to help decrease energy consumption and reduce spacecraft mass, cost, and fuel loading. Numerical simulations of such filters are very limited in the literature. Existing modeling approaches are based on the assumption of purely metallic (perfectly conducting) structures on substrates. however, in practice, metals have finite conductivity that can lead to power absorption in the metal. At optical frequencies the usual material properties and perfect electric conductor (PEC) assumption is not applicable. Moreover, the conventional methods, such as using resistive sheets or lossy dielectrics to simulate metallic losses, are not accurate. The goal is to provide a new approach for modeling metallic losses more accurately at the optical frequencies.

Purpose The aim of this research is to promote modeling transient heat and volatile organic compound (VOC) diffusion in multilayered materials with different thermophysical characteristics and irregular interfaces. Although lattice Boltzmann method (LBM) has exhibited considerable promise for steady-state transport, efforts are still needed in accurately addressing flux continuity on interfaces. This research applies and contrasts two methods: the diffuse interface approach, dependent on a smoothness parameter, and the special interface treatment (SIT), which imposes directly flux and field continuity. This is to assess their efficiency, compare with analytical and existing results and illustrate practical use for energy efficiency and indoor air quality control. Design/methodology/approach This study develops a lattice Boltzmann framework to model transient heat and VOC diffusion across multilayer materials with contrasting thermophysical properties and irregular boundaries. Two interface treatments were implemented: (1) the diffuse interface method, which smooths interfacial discontinuities using a tunable thickness parameter and (2) the SIT*, which directly enforces temperature/concentration and flux continuity without additional parameters. Numerical simulations were performed for porous and non-porous assemblies, Sandwich panels and room-scale models. Validation was conducted against analytical solutions and published data to ensure accuracy, robustness and practical applicability ([*]Mohamad et al., 2014). Findings This study demonstrates that while the diffuse interface LBM provides smoother transitions for heat diffusion at regular interfaces, its reliance on a tunable smoothness parameter can obscure sharp gradients and hinder calibration. In contrast, the SIT approach ensures strict continuity of temperature/concentration and fluxes without extra parameters, proving particularly effective for VOC diffusion in multilayer assemblies with abrupt property contrasts and sorption effects. Validation against analytical, numerical and literature results confirms its accuracy for layered materials, Sandwich panels and room-scale problems. Overall, the SIT-based framework offers a practical, reliable tool for optimizing multilayer systems in energy and indoor air applications. Originality/value This study is original in adapting and systematically comparing the diffuse interface method and the SIT within the LBM framework for transient heat and VOC diffusion in multilayer assemblies. While the diffuse interface approach smooths property jumps via a tunable parameter, SIT enforces strict flux and field continuity without extra calibration, offering a robust alternative for VOC transport where abrupt variations dominate. The originality lies in demonstrating SIT's practicality across layered walls, Sandwich panels and room-scale simulations, providing a validated, parameter-free tool with clear relevance to thermal management, energy efficiency and indoor air quality.

There are a number of composites available but cannot be used in the aircraft because they do not possess the required fire-resistant properties. The fire norms set by the aviation regulatory bodies are very stringent, in order to use any material in aircraft interiors, it should comply with FAR 25.853 norms. This regulation demands that each material in a multilayer material as well as its assembly should comply with the regulation. Therefore, in the present study, a multilayer composite material consisting of four layers is tested in an ISO 5660 cone calorimeter at the incident heat flux of 50 kW/m2. At first, all the constitute layers (i.e. paint, laminate, and honeycomb) are tested separately at the same heat flux (i.e. 50 kW/m2) to identify the thermal decomposition process of each material individually. Thereafter, step by step layers are added and three different assemblies are formed and tested under the same heat flux to identify the thermal interaction between each layer. The obtained results confirm that the time to attain the maximum surface temperature increases with an increase in the layers of materials. However, the peak surface temperature attained by the materials increases while the CO emission for the first 300 s decreases with the increase in the material layers.

We develop a microscopic theory for the multimode polariton dispersion in materials coupled to cavity radiation modes. Starting from a microscopic light-matter Hamiltonian, we devise a general strategy for obtaining simple matrix models of polariton dispersion curves based on the structure and spatial location of multilayered 2D materials inside the optical cavity. Our theory exposes the connections between seemingly distinct models that have been employed in the literature and resolves an ambiguity that has arisen concerning the experimental description of the polaritonic band structure. We demonstrate the applicability of our theoretical formalism by fabricating various geometries of multilayered perovskite materials coupled to cavities and demonstrating that our theoretical predictions agree with the experimental results presented here.

Within the nuclear-electronic orbital (NEO) framework, the real-time NEO time-dependent density functional theory (RT-NEO-TDDFT) approach enables the simulation of coupled electronic-nuclear dynamics. In this approach, the electrons and quantum nuclei are propagated in time on the same footing. A relatively small time step is required to propagate the much faster electronic dynamics, thereby prohibiting the simulation of long-time nuclear quantum dynamics. Herein, the electronic Born-Oppenheimer (BO) approximation within the NEO framework is presented. In this approach, the electronic density is quenched to the ground state at each time step, and the real-time nuclear quantum dynamics is propagated on an instantaneous electronic ground state defined by both the classical nuclear geometry and the nonequilibrium quantum nuclear density. Because the electronic dynamics is no longer propagated, this approximation enables the use of an order-of-magnitude larger time step, thus greatly reducing the computational cost. Moreover, invoking the electronic BO approximation also fixes the unphysical asymmetric Rabi splitting observed in previous semiclassical RT-NEO-TDDFT simulations of vibrational polaritons even for small Rabi splitting, instead yielding a stable, symmetric Rabi splitting. For the intramolecular proton transfer in malonaldehyde, both RT-NEO-Ehrenfest dynamics and its BO counterpart can describe proton delocalization during the real-time nuclear quantum dynamics. Thus, the BO RT-NEO approach provides the foundation for a wide range of chemical and biological applications.

Realizing strong coupling between a single quantum emitter (QE) and an optical cavity is of crucial importance in the context of various quantum optical applications. While Rabi splitting of single quantum emitters coupled to high-Q diffraction limited cavities have been reported in numerous configurations, attaining single emitter Rabi splitting with a plasmonic nanostructure is still elusive. Here, we establish the analytical condition for strong coupling between a single QE and a plasmonic nanocavity and apply it to study various plasmonic arrangements that were shown to enable Rabi splitting. We investigate numerically the optical response and the resulting Rabi splitting in metallic nanostructures such as bow-tie nanoantennas, nanosphere dimers and nanospheres on a surface and find the optimal geometries for emergence of the strong coupling regime with single QEs. We also provide a master equation approach to show the saturation of a single QE in the gap of a silver bow-tie nanoantenna. Our results will be useful for implementation of realistic quantum plasmonic nanosystems involving single QEs.

This paper introduces a shading model for light diffusion in multi-layered translucent materials. Previous work on diffusion in translucent materials has assumed smooth semi-infinite homogeneous materials and solved for the scattering of light using a dipole diffusion approximation. This approximation breaks down in the case of thin translucent slabs and multi-layered materials. We present a new efficient technique based on multiple dipoles to account for diffusion in thin slabs. We enhance this multipole theory to account for mismatching indices of refraction at the top and bottom of of translucent slabs, and to model the effects of rough surfaces. To model multiple layers, we extend this single slab theory by convolving the diffusion profiles of the individual slabs. We account for multiple scattering between slabs by using a variant of Kubelka-Munk theory in frequency space. Our results demonstrate diffusion of light in thin slabs and multi-layered materials such as paint, paper, and human skin.

This paper introduces a shading model for light diffusion in multi-layered translucent materials. Previous work on diffusion in translucent materials has assumed smooth semi-infinite homogeneous materials and solved for the scattering of light using a dipole diffusion approximation. This approximation breaks down in the case of thin translucent slabs and multi-layered materials. We present a new efficient technique based on multiple dipoles to account for diffusion in thin slabs. We enhance this multipole theory to account for mismatching indices of refraction at the top and bottom of of translucent slabs, and to model the effects of rough surfaces. To model multiple layers, we extend this single slab theory by convolving the diffusion profiles of the individual slabs. We account for multiple scattering between slabs by using a variant of Kubelka-Munk theory in frequency space. Our results demonstrate diffusion of light in thin slabs and multi-layered materials such as paint, paper, and human skin.

In noise control and other applications, porous sound-absorbing materials may be constructed of multiple layers of homogeneous materials. This work applies Bayesian inference to study and analyze such multilayer porous materials. The analysis utilizes a measurement of the overall material's acoustic surface impedance and a transfer-matrix porous material acoustic model. The number of layers present in the multilayer porous absorber under test and the physical properties of each layer are inversely determined. Bayesian model selection implements Occam's razor to determine the number of layers present in the sample, based on the measured impedance data and without any a priori knowledge of the number of layers. Once the number of layers has been determined, Bayesian parameter estimation inversely determines the physical properties of all layers simultaneously. A Markov chain Monte Carlo method, nested sampling, is applied to explore efficiently the high-dimensional parameter space inherent to this inverse p...