Dipolar Interactions Research Articles

Phases and coherence of strongly interacting finite bosonic systems in shallow optical lattice

We explore the ground states of strongly interacting bosons in the vanishingly small and weak lattices using the multiconfiguration time-dependent Hartree method for bosons (MCTDHB) which calculate numerically exact many-body wave function. Two new many-body phases: fragmented or quasi superfluid (QSF) and incomplete fragmented Mott or quasi Mott insulator (QMI) are emerged due to the strong interplay between short-range contact interaction and lattice depth. Fragmentation is utilized as a figure of merit to distinguish these two new phases. We utilize the eigenvalues of the reduced one-body density matrix and define an order parameter that characterizes the pathway from a very weak lattice to a deep lattice. We provide a detailed investigation through the measures of one- and two-body correlations and information entropy. We find that the structures in one- and two-body coherence are good markers to understand the gradual built-up of intra-well correlation and decay of inter-well correlation with increase in lattice depth. For the dipolar interaction, the many-body features become more distinct and true Mott state can appear even in a shallow lattice. Whereas, for incommensurate fraction of particles, incomplete localization happens that exhibits distinct features in the measure of two-body coherence.

Dipolar induced nonreciprocal magnon hybridization in FeNi/YIG bilayers

We investigated the magnon hybridization behavior in FeNi films, which were deposited on the yttrium-iron garnet (YIG) films by using Brillouin light scattering. Nonreciprocal magnon hybridizations have been detected not only on the mode densities but also the dispersion relations. The perpendicular standing spin wave mode confined in the thickness direction hybridized with the top surface magnetostatic surface spin wave at smaller wave vectors range while hybridized with the bottom surface mode at larger wave vectors range. The dipolar interaction between the FeNi layer and the YIG layer should be the main reason for the nonreciprocal hybridization of the two modes in the FeNi layer. The nonreciprocal hybridization characteristics of FeNi/YIG double-layer magnetic films enrich the nonreciprocal magnon hybridization system and might have potential application in constructing spin wave-based devices.

Adsorption Behavior and Mechanism of Brilliant Green Dye onto Acid-modified Mesoporous Volcanic Pumice

Water pollution is a major problem in the environment. The important one is the dying effluent from the textile industry. Dye effluent has affected human health and aquatic life. Recently, natural adsorbents have been most commonly used for dye treatment wastewater. This study explores the adsorption mechanism of brilliant green onto HCl-modified pumice. It involves a comparative analysis of the raw and HCl-modified pumice's characterization and adsorption properties. The adsorption experiments were carried out by considering several parameters, such as pH, contact time, initial dye concentrations, and temperatures. The research indicated that the raw and acid-treated pumice possess Si-OH and Si-O-Si groups. These pumice adsorbents are classified as mesoporous, exhibiting BJH pore diameters of 3.23 nm for the raw form and 3.69 nm for the acid-modified variant. The adsorption data revealed that the uptake of brilliant green dye was maximal at a pH of 8. The equilibrium results closely matched the Langmuir isotherm model. The maximum adsorption capacities were 37.13, 40.17, and 42.73 mg g-1 for the raw pumice, and 46.72, 51.81, and 56.17 mg g-1 for the modified pumice at 20, 30, and 40 °C, respectively. Furthermore, the removal efficiency of brilliant green dye with modified pumice was 91.93%, 95.29%, and 96.27% at 20°C, 30°C, and 40°C, respectively. The pseudo-second-order model was the most suitable for elucidating the kinetic adsorption data. The thermodynamic analysis revealed that the adsorption process was endothermic, spontaneous, and physical. Dipole-dipole H-bonding interaction, Yoshida H-bonding, electrostatic interaction, n-𝝅 interaction, cation exchange, and pore filling were all engaged in its process. Consequently, the local pumice volcanic rock became a great, cheap, abundant, and environmentally friendly adsorbent for removing dyes from effluents.

Tunable dipole–dipole interactions between nanoparticles levitated by two orthogonally polarized optical traps

Arrays of optically levitated nanoparticles with fully tunable light-induced dipole–dipole interactions have emerged as a platform for fundamental research and sensing applications. However, previous experiments utilized two optical traps with identical polarization, leading to an interference effect. Here, we demonstrate light-induced dipole–dipole interactions using two orthogonally polarized optical traps. Furthermore, we achieve control over the strength and polarity of the optical coupling by adjusting the polarization and propose a method to simultaneously and stably measure conservative and non-conservative coupling rates. Our results provide a new scheme for exploring entanglement and topological phases in arrays of levitated nanoparticles.

Stretchable and thermo-mechanical stable ionogels with high thermoelectric properties for respiratory sensing and energy harvesting

Flexible and wearable thermoelectrics have attracted much attention due to their unique capability of converting body heat into electricity. However, the trade-off between good mechanical properties and high thermopower remains a big challenge. Herein, a general concept based on synergistic ion-ion/ion–dipole interactions and chemical-physical networks to fabricate ionic thermoelectric (i-TE) ionogels with outstanding mechanical properties and ultrahigh thermoelectric performances is developed. The as-prepared ionogel demonstrates high mechanical stretchability of up to 1160 %, ultralow hysteresis of 4.6 %, tensile strength of 5.25 MPa, toughness of 22.09 MJ/m3, as well as outstanding thermo-mechanical stability and temperature tolerance from −99 to 250 °C. Importantly, the ionogel exhibits a giant ionic Seebeck coefficient (Si) up to 28.43 mV K−1, superior ionic conductivity of 35.3 mS cm−1, and impressive power factor (PF) of 2.85 mW m−1·K−2 at 90 RH%. As a result, a record high ionic thermoelectric figure of merit (ZTi) of 6.9 is obtained. Stretchable thermoelectric materials are endowed with both giant thermovoltage and ZTi is rarely achieved in previous studies. Furthermore, the application in flexible and wearable i-TE sensors and energy harvesters is demonstrated to convert heat into electricity for sensing and human body energy harvesting. Therefore, the as-prepared stretchable i-TE materials show amazing potential for advanced wearable self-powered ionotronics.

Active string fluids and gels formed by dipolar active Brownian particles in 3D.

Self-propelled particles possessing permanent magnetic dipole moments occur naturally in magnetotactic bacteria and can be built into man-made systems such as active colloids or micro-robots. Yet, the interplay between self-propulsion and anisotropic dipole-dipole interactions on dynamic self-assembly in three dimensions (3D) remains poorly understood. We conduct Brownian dynamics simulations of active dipolar particles in 3D, focusing on the low-density regime, where dipolar hard spheres tend to form chain-like aggregates and percolated networks with increasing dipolar coupling strength. We find that strong active forces override dipolar attractions, effectively inhibiting chain-like aggregation and network formation. Conversely, activating particles with low to moderate forces results in a fluid composed of active chains and rings. At strong dipolar coupling strengths, this active fluid transitions into an active gel, consisting of a percolated network of active chains. Although the overall structure of the active gel remains interconnected, the network experiences more frequent configurational rearrangements due to the reduced bond lifetime of active dipolar particles. Consequently, particles exhibit enhanced translational and rotational diffusion within the active fluid of strings and active gels compared to their passive counterparts. We quantify the influence of activity on aggregate topology as they transition from branched structures to unconnected chains and rings. Our findings are summarized in a state diagram, delineating the impact of dipolar coupling strength and active force magnitude on the system.

The reverse-DADI method: Computation of frequency-dependent atomic polarizabilities for carbon and hydrogen atoms in hydrocarbon structures

A specific method, combining some ingredients of the well-known DDA and PDI approaches, has been developed in our group since many years to calculate the absorption cross-sections of carbonaceous nanoparticles based on their atomistic details. This method, here named the Dynamic Atomic Dipole Interaction (DADI) model, requires the knowledge of the position and frequency-dependent polarizability of each atom constituting the nanoparticles. While the atomic positions can be quite easily obtained, for example as the results of molecular dynamics simulations, obtaining the frequency-dependent atomic polarizabilities is a trickier task. Here, a fitting procedure, named the reverse-DADI method, has been applied to calculate the frequency-dependent atomic polarizability values for carbon and hydrogen atoms involved in aromatic cycles or in aliphatic chains, on the basis of frequency-dependent molecular polarizabilities of various PAH and alkane molecules, calculated with the TD-DFT theory, in the UV–Visible range. Then, using these frequency-dependent atomic polarizabilities as input parameters in the DADI model has been shown to lead to an accurate representation of the absorption cross-sections of various PAH and alkane molecules with respect to the corresponding values obtained at the TD-DFT level, with however the great advantage of a much shorter time of calculations. Furthermore, these results are indications of a good transferability of the frequency-dependent atomic polarizability values obtained here to any C or H atom of any PAH or alkane molecule. This opens the way for building large databases of optical properties for carbonaceous species of atmospheric or astrophysical interests.

Resonant Dipole–Dipole Interaction: A Protocol to Amplify Weaker PL Emission in 2D MoS2

Resonant Dipole–Dipole Interaction: A Protocol to Amplify Weaker PL Emission in 2D MoS₂

Continuous Focusing of Particles by AC-Electroosmosis and Induced Dipole Interactions.

Continuous particle focusing by using microfluidics is an effective method for separating particles, cells, or droplets for analytical purposes. Previously, it was shown that an alternating current across rectangular microchannels with slightly deformed side walls results in vortex flow patterns caused by alternating current electroosmosis (AC-EOF) and could lead to particle focusing. In this work, we explore this mechanism by experimentally studying the particle focusing behavior for various fluid flow velocities through a microchannel. Since it is unlikely that the particles are kept in their focused position solely by convection, a theoretical force balance between the hydrodynamic and the induced dipole force was determined. In our experiments, it was found that there is no substantial effect of the pressure-driven fluid velocity on the particle focusing velocity within the studied range. From the theoretical force balance calculations, it was determined that while the addition of the induced dipole force can still not completely describe the experimentally observed particle focusing, the induced dipole can be strong enough to overcome the hydrodynamic force. Finally, it is hypothesized that under specific circumstances, including a repulsive electrostatic force between a particle and electrode wall can complete the theoretical particle focusing force balance. Alternative phenomena that could also play a role in particle focusing are proposed.

Power-law-exponential interaction induced quantum spiral phases

We theoretically predict a kind of power-law-exponential (PLE) dipole-dipole interaction between quantum emitters in a 1D waveguide QED system. This unconventional long-range interaction is the combination of power-law growth and exponential decay couplings. Applying the PLE interaction to a spin model, we uncover the rich many-body phases. Most remarkably, we find that the PLE interaction can induce the ordered and critical spiral phases. These spiral phases emerge from the strong frustration generated by the power-law factor of the PLE interaction; hence they are absent for other types of long-range interaction, e.g., pure exponential and power-law decay interactions. Our work is also applicable for the higher-dimensional systems. It fundamentally broadens the realm of many-body physics and has significant applications in quantum simulation of strongly correlated matter. Published by the American Physical Society 2024

Fabrication of Flexible Wearable Mechanosensors Utilizing Piezoelectric Hydrogels Mechanically Enhanced by Dipole-Dipole Interactions.

Conductive hydrogels have been increasingly employed to construct wearable mechanosensors due to their excellent mechanical flexibility close to that of soft tissues. In this work, piezoelectric hydrogels are prepared through free radical copolymerization of acrylamide (AM) and acrylonitrile (AN) and further utilized in assembling flexible wearable mechanosensors. Introduction of the polyacrylonitrile (PAN) component in the copolymers endows the hydrogels with excellent piezoelectric properties. Meanwhile, significant enhancement of mechanical properties has been accessed by forming dipole-dipole interactions, which results in a tensile strength of 0.51 MPa. Flexible wearable mechanosensors are fabricated by utilizing piezoelectric hydrogels as key signal converting materials. Self-powered piezoelectric pressure sensors are assembled with a sensitivity (S) of 0.2 V kPa-1. Additionally, resistive strain sensors (gauge factor (GF): 0.84, strain range: 0-250%) and capacitive pressure sensors (S: 0.23 kPa-1, pressure range: 0-8 kPa) are fabricated by utilizing such hydrogels. These flexible wearable mechanosensors can monitor diverse body movements such as joint bending, walking, running, and stair climbing. This work is anticipated to offer promising soft materials for efficient mechanical-to-electrical signal conversion and provides new insights into the development of various wearable mechanosensors.

Quantum sensing of ultralow temperature in biwire ultracold polar molecules

We present a systematic study of quantum sensing of ultralow temperature in biwire ultracold polar molecules of a quasi-one-dimensional (1D) trap by exploring the dynamics of two physically different qubit models. The two models consist of a trapped impurity atom that act as a temperature quantum sensor interacting with polar molecules reservoir, where dipole moments are aligned head-to-tail across the wires. Our model takes advantage of the adjustable interwire distance to accurately control the precision ultralow temperatures measurement. We show that the system undergoes a transition from Markovian to non-Markovian dynamics, which can be controlled by changing the interwire separation, the dipole-–dipole interaction (DDI), and the temperature. We characterize the thermometric performance using the quantum signal-to-noise ratio for both models and demonstrate that such a quantity exhibits a higher peak at ultralow temperature. We therefore emphasize that ultracold polar molecules are crucial for revolutionizing temperature sensing. Published by the American Physical Society 2024

A samarium (Ⅲ)-activated tantalum-based double perovskite phosphor with high thermostability

Inorganic double perovskite phosphor materials have received much attention in solid-state lighting domain due to efficient and versatile luminescence colors. This study employs a high-temperature solid-phase method to synthesize a series of Sm3+-activated Sr2YTaO6 (SYTO):Sm3+ phosphors with double perovskite structure. The structure, morphology, and content/temperature-dependent orange-red emissions are thoroughly elucidated. For SYTO:3 mol%Sm3+, the luminescence intensity at 423 K remains 95 % of that at 298 K, verifying high thermostability. Meanwhile, the phosphor exhibits good resistance to color shifting. A high Sm3+ content induces luminescence quenching due to dipole–dipole interaction. Finally, the synthesized material is utilized to fabricate a satisfactory and warm white light-emitting diode.

Highly efficient Dy3+ activated Sr9Al6O18 nanophosphors for W-LEDs, optical thermometry and deep learning-based intelligent system for personal identification applications

A novel single-phase Dy3+ activated Sr9Al6O18 nanophosphors (NPs) was synthesized using a solution combustion method with urea as the fuel. When phosphors are excited at 350 nm, their photoluminescence (PL) spectra exhibit strong emissions at 484 and 574 nm, which are associated with the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions. These emissions are attributed to magnetic and electric dipole allowed transitions, correspondingly. It is found that dipole–dipole interactions are the main source of concentration quenching and energy transfer among the activator ions. The prepared NPs show thermal stability up to 480 K having an activation energy (Ea) of 0.2437 eV, as determined by temperature-dependent photoluminescence (TDPL). With a remarkable internal quantum efficiency (IQE) of 66.14 %, the optimized phosphor achieves notable relative sensitivity (Sr) and absolute sensitivity (Sa), estimated to be 2.65 % K−1 and 1.38×10−3 K−1 at 300 K, respectively. Thus, Sr9Al6O18:Dy3+ is a promising material for non-contact optical thermometry applications. Latent fingerprints (LFPs) and latent lip prints (LLPs) can be efficiently produced on a variety of surfaces by using the optimized NPs with the simple powder dusting technique. The prints are made visible under UV light with a 365 nm wavelength. The You Only Look Once version 8 (YOLOv8x) approach analyzes the overall morphological correlations of different minutiae to identify essential minutiae that indicate the identities of people from FPs. Splitting and matching multi-scale fingerprints (FPs) features improves the validity of the authenticating findings. The results show that the recommended method, which improves the entire FP authentication process, offers exceptional accuracy, resilience and speed. The findings provide strong support for the implementation of the optimized NPs in photonic devices, optical thermometers, and advanced forensic applications.

Molecular interaction studies of L-proline in water and ethanol at different temperatures using dielectric relaxation, refractive index and DFT methods

The complex dielectric permittivity of L-Proline in water and ethanol solutions with molar concentrations ranging from 0.025 M to 0.15 M was measured by open-ended coaxial probe technique. The measurements were carried out across a frequency span of 0.02 < ν/GHz < 20 and temperatures varying from 298.15 K to 323.15 K. The densities (ρ) and refractive index (nD ) of the L-proline in aqueous and ethanol solutions were also determined to provide insights into the solute-solvent interactions in the system. The Havriliak-Negami equation was employed to compute the dielectric relaxation time of the mixtures. The relaxation time of L-Proline in an ethanol medium was found to be higher than that of L-Proline in an aqueous medium due to the greater degree of self-association of ethanol molecules. Additionally, the relaxation time of the mixtures lengthened with rising molar concentration, which is attributed to the presence of hydrogen bonds among L-Proline and aqueous/ethanol molecules. The strength of the hydrogen bond interaction of L-Proline in both mediums was calculated using single-point energy calculations employing IEFPCM/PCM solvation models through DFT/B3LYP and MP2 approaches with a 6-311 G ++ (d, p) basis set. The results were correlated with the hydrogen bond strength, Gibbs’ free energy of activation parameter, and dipole-dipole interactions. Communicated by Ramaswamy H. Sarma

A Study of Degenerate Four‐Wave Mixing and Phase Conjugation in Metallic Nanohybrids

AbstractA theory of degenerate four‐wave mixing (DFWM) and phase conjugation is developed for metallic nanohybrids, which consist of an ensemble of interacting metallic nanoshells and noninteracting quantum dots (QDs). It is considered that three incident waves are applied to the metallic nanohybrid, and they produce a fourth output mixed wave. These waves induce dipoles in metallic nanoshells, generating surface plasmon polaritons, and interact with each other via the dipole–dipole interactions (DDI). In DFWM, the input and output waves travel in opposite directions, and this retroreflective nature is responsible for the phenomenon of phase conjugation. The analytical expressions for the input transmitted and output reflected wave intensities are calculated in the presence of the surface plasmon polaritons (SPPs) and the DDI polaritons. It is demonstrated that the phase conjugation, the phase coherent phenomena, and the intensities of both input transmitted and output reflected waves are enhanced due to SPPs and DDI polaritons. These findings indicate that the nanohybrid acts as a phase conjugate device and a phase coherent optical amplifier, which can be applied to fabricate optical nanoamplifiers, phase conjugate mirrors, and nanosensors by measuring the intensity of the output reflected wave.

Classical spin models and basic magnetic interactions on 1/1-approximant crystals

We study classical spin models on the 1/1 Tsai-type approximant lattice using Monte Carlo and mean-field methods. Our aim is to understand whether the phase diagram differences between Gd- and Tb-based approximants can be attributed to anisotropy induced by the crystal-electric field. To address this question, we treat Gd ions as Heisenberg spins and Tb ions as Ising spins. Additionally, we consider the presence of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction to replicate the experimentally observed correlation between magnetic properties and electron concentration. Surprisingly, our findings show that the transition between ferromagnetic and antiferromagnetic order remains unaltered by the anisotropy, even when accounting for the dipole interaction. We conclude that a more comprehensive model, extending beyond the free-electron gas RKKY interaction, is likely required to fully understand the distinctions between Gd- and Tb-based approximants. Our work represents a systematic exploration of the impact of anisotropy on the ground-state properties of classical spin models in quasicrystal approximants. Published by the American Physical Society 2024

Introducing macrocyclic glycopeptide columns as unique achiral stationary phases: Insights from hydrophobic subtraction model and in-silico modeling

BackgroundThe need for stationary phases with unique selectivity in reversed-phase liquid chromatography has been of utmost importance to chromatographers for advancing the analysis of complex samples. Macrocyclic glycopeptide based stationary phases have been widely used for chiral separations with different chromatographic modes such as normal phase, reversed phase, and supercritical fluid chromatography. Given the multimodal retention mechanisms namely π-π complex interaction, hydrogen bonding, dipole-dipole interaction, and strong Coulombic interactions by which analytes are separated using the macrocyclic glycopeptides, these stationary phases are expected to provide novel selectivity when used under the reversed phase for achiral separations. ResultsHerein, for the first time we have conducted a systematic study using the improved hydrophobic subtraction model (HSM) which incoporates dipole-dipole interactions to demonstrate the novel selectivity offered by four different macrocyclic glycopeptide based stationary phases, namely NicoShell, TeicoShell, TagShell, and VancoShell. A comparison of the HSM parameters for these columns has been made with 551 commercially available reversed phase stationary phases and the differences in the values point to the importance of adding these columns to the already existing arsenal. These stationary phases offer separations over a wide range of pH and show variability in selectivity depending on the pH of the mobile phase which make them versatile for method development in the reversed phase mode. Additionally, we have provided an actual example of a separation from an Amgen discovery project using the VancoShell column aided by computer-assisted modelling. SignificanceThis is the first report characterizing macrocyclic glycopeptides for achiral RPLC applications. The selectivity of these stationary phases were found to be unique when compared to other commercially available stationary phases thereby acting as their own class of columns. The unusual selectivity of the columns enabled separation of complex pharmaceutical samples.

Bonding and antibonding electromagnetic coupling in two interacting toroidal metamolecules

The existence of a toroidal-like eigenmode and its electromagnetic coupling in a system of dielectric particles are studied. A constituent structure (metamolecule) is made of a ring consisting of the radial arrangement of several vertically standing dielectric disks (meta-atoms). In the eigenstate of the given metamolecule, the second-order term related to the exact electric dipole in the multipole decomposition is much greater than the first-order term. This eigenstate is defined as a toroidal-like mode. Then, the characteristics of a system (metamacromolecule) composed of two identical rings are studied in both eigen- and excited states to reveal the peculiarities of the toroidal-like mode coupling. Similar to the well-known electric dipole-dipole and magnetic dipole-dipole interactions, the interaction of toroidal-like modes also appears in symmetric (bonding) and antisymmetric (antibonding) forms. Their excitation in the metamacromolecule depends on the propagation direction and polarization of the irradiating wave. The manifestation of toroidal-like mode coupling is confirmed by checking the extinction cross section and near-field distributions obtained from the full-wave numerical simulation and microwave experiment. A clear understanding of the nature of toroidicity is important from the fundamental physics perspective and practical implementation of metamaterials operated in such exotic states. Published by the American Physical Society 2024

Universality of Efimov states in highly mass-imbalanced cold-atom mixtures with van der Waals and dipole interactions

We study three-body systems in a mass-imbalanced, two-component, cold-atom mixture, and we investigate the three-body parameter of their Efimov states for both bosonic and fermionic systems, with a major focus on the Er-Er-Li Efimov states. For a system interacting solely via van der Waals interactions, the van der Waals universality of the three-body parameter is analytically derived using the quantum defect theory. With the addition of a perturbative dipole interaction between the heavy atoms, the three-body parameters of the bosonic and fermionic Efimov states are found to behave differently. When the dipole interaction is as strong as the van der Waals interaction, corresponding to realistic Er-Er-Li Efimov states, we show that the van der Waals universality persists once the effects of the nonperturbative dipole interaction are into the s-wave and p-wave scattering parameters between the heavy atoms. For a dipole interaction much stronger than the van der Waals interaction, we find that the universality of the Efimov states can be alternatively characterized by a quasi-one-dimensional scattering parameter due to a strong anisotropic deformation of the Efimov wave functions. Our work thus clarifies the interplay of isotropic and anisotropic forces in the universality of the Efimov states. Based on the renormalized van der Waals universality, the three-body parameter is estimated for specific isotopes of Er-Li cold-atom mixtures. Published by the American Physical Society 2024