Nonlocal Response Research Articles

Exploiting universal nonlocal dispersion in optically active materials for spectro-polarimetric computational imaging

Recent years have seen significant advancements in exploring novel light-matter interactions such as hyperbolic dispersion within natural crystals. However, current studies have predominantly concentrated on local optical response of materials characterized by a dielectric tensor without spatial dispersion. Here, we investigate the nonlocal response in optically-active crystals with screw symmetries, revealing their lossless, super-dispersive properties compared to traditional optical response functions. We leverage this universal nonlocal dispersion, i.e. the dispersion of optical rotatory power, to explore a novel spectral de-multiplexing scheme compared to conventional gratings, prisms and metasurfaces. We design and demonstrate an ‘Nonlocal-Cam’ - a camera that exploits nonlocal dispersion through sampling of polarized spectral states and the application of computational spectral reconstruction algorithms. The Nonlocal-Cam captures information in both laboratory and outdoor field experiments which is unavailable to traditional intensity cameras - the spectral texture of polarization. Merging the fields of nonlocal electrodynamics and computational imaging, our work paves the way for exploiting nonlocal optics of optically active materials in a variety of applications, from biological microscopy to physics-driven machine vision and remote sensing.

Comparative analysis of theories accounting for quantum effects in plasmonic nanoparticles

Understanding and accounting for quantum effects in nanoplasmonics is essential for accurate modeling and design of nanophotonic devices. In this paper, we investigate the influence of such quantum effects as spatial nonlocality and splitting of the wave function of conduction electrons near the surface of plasmonic nanoparticles on the extinction cross-section and the field enhancement factor. We apply the theory of generalized nonlocal optical response (GNOR) to describe the spatial nonlocality of noble metal particles. To consider the behavior of electrons near the metal–dielectric interface, mesoscopic boundary conditions are used, including the surface response functions (SRF) - the Feibelman parameters. We use the discrete source method (DSM), allowing for numerical analysis of the scattering problems taking into account quantum effects in the frame of both theories. The application of both GNOR and SRF approaches leads to a decrease in the amplitude of the plasmon resonance compared to the classical Maxwell theory and its shift to the shorter wavelength region (blue shift). The simulation results demonstrate significant differences between the two theories explaining the quantum effects arising in non-spherical plasmonic nanoparticles located in a dense environment. Specifically, compared with GNOR theory, SRF predicts a larger field enhancement. We found that quantum nonlocal effects are more significant for the enhancement factor at the particle surface than for the extinction cross-section. In addition, it was discovered that a denser environment leads to a significant increase in the blue shift of the plasmonic peak.

General theory of cavity-mediated interactions between low-energy matter excitations.

The manipulation of low-energy matter properties such as superconductivity, ferromagnetism, and ferroelectricity via cavity quantum electrodynamics engineering has been suggested as a way to enhance these many-body collective phenomena. In this work, we investigate the effective interactions between low-energy matter excitations induced by the off-resonant coupling with cavity electromagnetic modes. We extend a previous work by going beyond the dipole approximation accounting for the full polarization and magnetization densities of matter. We further include the often neglected diamagnetic interaction and, for the cavity, we consider general linear absorbing media with possibly non-local and non-reciprocal response. We demonstrate that, even in this general scenario, the effective cavity-induced interactions between the matter degrees of freedom are of electrostatic and magnetostatic nature. This confirms the necessity of a multimode description for cavity engineering of matter systems where the low-energy assumption holds. Our findings provide a theoretical framework for studying the influence of general optical environments on extended low-energy matter excitations.

Control of the local and nonlocal electromagnetic response in all-dielectric reconfigurable metasurfaces

Control of the local and nonlocal electromagnetic response in all-dielectric reconfigurable metasurfaces

Non-local optical response of a multi-phased quantum material

Non-local optical response of a multi-phased quantum material

Acute local and non-local morphological, sensory and fluid responses to stretching and foam rolling in young females

BackgroundThis study aimed to compare and examine the local and non-local effects of a foam rolling (FR) and static stretching (SS) intervention applied to the plantar flexor (PF). MethodsFourteen female participants were investigated. Each participant underwent three conditions in a random order at least 48h apart and at the same time of the day: Control (CC), SS, and FR. Each condition was performed unilaterally in the dominant PF for 4 sets (apart from CC). SS was performed for 30 s. The FR included 30 rolls (15 in each direction) over a period of 30 s. A rest of 30 s was provided between each set for all conditions. Outcome variables were ankle dorsiflexion range of movement (ROM), tissue hardness, localized bioimpedance analysis at 50 kHz (L-BIA), and pain pressure thresholds (PPT). Tissue hardness, L-BIA, and PPT were measured in the lower leg and thigh. Measures were assessed pre (T0), immediately post (T1), and 10-min after (T2) the intervention. ResultsNo differences were found for time for the CC or between the T0 of each condition. Concerning the lower leg, ROM improved for SS and FR from T0 to T1 while returning to baseline in T2. A significant increase in PPT was observed only for SS in T1. L-BIA showed a significant increase for both phase angle and impedance only for FR in T1. Tissue hardness did not change for any group at any time-point. Concerning the thigh, no measure at any time point showed significant differences. ConclusionBoth, FR and SS were able to acutely improve ankle ROM. The observed changes were probably caused by a change in viscoelastic properties and local pain perception, without any variation in tissue morphology. FR was the only intervention to improve the intracellular-to-extracellular ratio and decrease fluids. Non-local effects were not observed.

Nonlocal dynamic response of FGP sandwich microbeam with 2D PSH network incorporating adatoms-surface interactions energy under magnetic field

The present work models and studies the resonance frequency change due to adsorption phenomena in a simply-supported adatom-microbeam system under an axial magnetic environment. The microbeam structure is a functionally graded (FG) sandwich that includes a rectangular configuration and a ceramic perforated core with periodic square holes network and FG porous material faces. To evaluate the adsorption-induced energies produced by van der Waals interaction (vdW), the Morse and Lennard-Jones (6–12) potentials are included in conjunction with nonlocal material elasticity to adopt the small-scale impact. Moreover, the explicit formulas for the inertia moments and shear force are developed by the Timoshenko beam equations, considering the residual stress influence as an additional axial load. The Navier-type solution and the differential quadratic method (DQM) are implemented to compute the solution of the governing equations. It is established that the resonance frequency change for the O/Si (100) and H/Si (100) is dependent on the geometrical, perforation, and porosity parameters, adsorption density, mode number, and the magnetic field intensity as well. Therefore, these numerical results have been discussed in detail to properly examine dynamic vibration behavior and a suitable mass detection design of M/NEMS structures.

Collective dynamics and long-range order in thermal neuristor networks

In the pursuit of scalable and energy-efficient neuromorphic devices, recent research has unveiled a novel category of spiking oscillators, termed “thermal neuristors.” These devices function via thermal interactions among neighboring vanadium dioxide resistive memories, emulating biological neuronal behavior. Here, we show that the collective dynamical behavior of networks of these neurons showcases a rich phase structure, tunable by adjusting the thermal coupling and input voltage. Notably, we identify phases exhibiting long-range order that, however, does not arise from criticality, but rather from the time non-local response of the system. In addition, we show that these thermal neuristor arrays achieve high accuracy in image recognition and time series prediction through reservoir computing, without leveraging long-range order. Our findings highlight a crucial aspect of neuromorphic computing with possible implications on the functioning of the brain: criticality may not be necessary for the efficient performance of neuromorphic systems in certain computational tasks.

Tailoring Space-Time Nonlocality for Event-Based Image Processing Metasurfaces.

Analog computation with passive optical components can enhance processing speeds and reduce power consumption, recently attracting renewed interest thanks to the opportunities enabled by metasurfaces. Basic image processing tasks, such as spatial differentiation, have been recently demonstrated based on engineered nonlocalities in metasurfaces, but next-generation computational schemes require more advanced capabilities. Here, by simultaneously tailoring the nonlocal electromagnetic response of a metasurface in space and time, we demonstrate a passive ultrathin silicon-based device that performs mixed spatiotemporal differentiation of input images, realizing event-based edge detection. The metasurface performs spatial differentiation only when the input image is evolving in time, resulting in spatiotemporal image processing on subpicosecond timescales. Moreover, the metasurface design can be tailored to selectively enhance objects moving at desired speeds. Our results point towards fully passive processing of spatiotemporal signals, for highly compact neuromorphic cameras.

Anti-Coulomb ion-ion interactions: A theoretical and computational study

The free energy of ion solvation can be decomposed into enthalpic and entropic contributions. This helps one to understand the connection between the dielectric properties and the underlying forces. We present a simple linear-response model of screened charge interactions that provides an alternative understanding of solvation barriers. Moreover, it explains the “anti-Coulomb” interactions (attraction between like-charged ions and repulsion between opposite-charged ions) observed in both simulations and experiments. We show that this is a universal behavior associated to the nonlocal response function of any dielectric or metallic systems. Published by the American Physical Society 2024

Multiple Functional Protein-Protein Interaction Interfaces Allosterically Regulate ATP-Binding in Cyclin-Dependent Kinase-1.

The ATP-dependent phosphorylation activity of cyclin-dependent kinase 1 (CDK1), an essential enzyme for cell cycle progression, is regulated by interactions with Cyclin-B, substrate, and Cks proteins. We have recently shown that active site acetylation in CDK1 abrogated binding to Cyclin-B which posits an intriguing long-range communication between the catalytic site and the protein-protein interaction (PPI) interface. Now, we demonstrate a general allosteric link between the CDK1 active site and all three of its PPI interfaces through atomistic molecular dynamics (MD) simulations. Specifically, we examined ATP binding free energies to CDK1 in native nonacetylated (K33wt) and acetylated (K33Ac) forms as well as the acetyl-mimic K33Q and the acetyl-null K33R mutant forms, which are accessible in vitro. In agreement with experiments, ATP binding is stronger in K33wt relative to the other three perturbed states. Free energy decomposition reveals, in addition to expected local changes, significant and selective nonlocal entropic responses to ATP binding/perturbation of K33 from the -helix, activation loop (A-loop), and - H segments in CDK1 which interface with Cyclin-B, substrate, and Cks proteins, respectively. Statistical analysis reveals that while entropic responses of protein segments to active site perturbations are on average correlated with their dynamical changes, such correlations are lost in about 9%-48% of the dataset depending on the segment. Besides proving the bi-directional communication between the active site and the CDK1:Cyclin-B interface, our study uncovers a hitherto unknown mode of ATP binding regulation by multiple PPI interfaces in CDK1.

Nonlocal structural effects of water on DNA homology recognition

The mechanism behind mutual recognition of homologous DNA sequences prior to genetic recombination is one of the remaining puzzles in molecular biology. Leading models of homology recognition, based on classical electrostatics, neglect the short-range nonlocal screening effects arising from structured water around DNA, and hence may only provide insight for relatively large separations between interacting DNAs. We elucidate the role of the effects of the nonlocal dielectric response of water on DNA–DNA interaction and show that these can dramatically enhance the driving force for recognition.

Water structural effects on DNA–DNA interactions and homologous recognition

Comprehending the principles underlying the interaction between DNA molecules in electrolyte solution is of crucial importance for understanding the phenomena of DNA condensation, recognition of homologous genes, and properties of DNA liquid crystals. Although DNA was considered in all its helical complexity over the last two decades, only a primitive, local, electrostatic model of the aqueous solution was considered. The forces acting between DNA molecules however must be influenced by the structure of the liquid separating them. In this paper we make a step towards unravelling earlier neglected effects of water structure on DNA–DNA interactions. We develop a model of DNA interaction accounting for the nonlocal dielectric response of water and of the electrolyte plasma dissolved in it. We focus particularly on the study of the dipolar overscreening effect, which leads to decaying oscillations of the electrostatic potential about DNA, and how it will affect electrostatic energy surfaces as a function of interaxial separation and mutual azimuthal orientation of the parallelly aligned interacting DNAs. We found that going beyond the classical electrostatic description of water (the so-called primitive model) reveals a complex oscillatory interaction surface in space, with many possible metastable configurations. These however vanish rapidly with smearing of the DNA charge distribution, due to dephasing of the oscillatory components of the interaction. This dephasing results in the suppression of oscillation amplitudes and leads to the dominance of non-oscillatory components in spatial dipolar correlations and the Debye screening. These dominant correlation patterns are shown to lead to a substantial enhancement of the difference between the interaction of homologous and nonhomologous DNA sequences, deepening and sharpening the homology recognition well.

Effect of the Contribution of the Local and Nonlocal Optical Response of an Isotropic Gyrotropic Medium on the Components of the Minkowski Energy–Momentum Tensor of the Electromagnetic Field of the Self-Focusing Beam

Effect of the Contribution of the Local and Nonlocal Optical Response of an Isotropic Gyrotropic Medium on the Components of the Minkowski Energy–Momentum Tensor of the Electromagnetic Field of the Self-Focusing Beam

Reconfigurable image processing metasurfaces with phase-change materials.

Optical metasurfaces have enabled analog computing and image processing within sub-wavelength footprints, and with reduced power consumption and faster speeds. While various image processing metasurfaces have been demonstrated, most of the considered devices are static and lack reconfigurability. Yet, the ability to dynamically reconfigure processing operations is key for metasurfaces to be used within practical computing systems. Here, we demonstrate a passive edge-detection metasurface operating in the near-infrared regime whose response can be drastically modified by temperature variations smaller than 10 °C around a CMOS-compatible temperature of 65 °C. Such reconfigurability is achieved by leveraging the insulator-to-metal phase transition of a thin layer of vanadium dioxide, which strongly alters the metasurface nonlocal response. Importantly, this reconfigurability is accompanied by performance metrics-such as numerical aperture, efficiency, isotropy, and polarization-independence - close to optimal, and it is combined with a simple geometry compatible with large-scale manufacturing. Our work paves the way to a new generation of ultra-compact, tunableand passive devices for all-optical computation, with potential applications in augmented reality, remote sensing and bio-medical imaging.

Modulation instability in nonlinear media with sine-oscillatory nonlocal response function and pure quartic diffraction.

Modulation instability of one-dimensional plane wave is demonstrated in nonlinear Kerr media with sine-oscillatory nonlocal response function and pure quartic diffraction. The growth rate of modulation instability, which depends on the degree of nonlocality, coefficient of quartic diffraction, type of the nonlinearity and the power of plane wave, is analytically obtained with linear-stability analysis. Different from other nonlocal response functions, the maximum of the growth rate in media with sine-oscillatory nonlocal response function occurs always at a particular wave number. Theoretical results of modulation instability are confirmed numerically with split-step Fourier transform. Modulation instability can be controlled flexibly by adjusting the degree of nonlocality and quartic diffraction.

Full wave modeling of radio-frequency beams in tokamaks in the electron cyclotron frequency range

Simulation of full wave, without paraxial approximation, high-resolution solution of wave equations in frequency domain in the electron cyclotron resonance (ECR) frequency range for realistic Tokamak plasma parameters became possible by using recently formulated hybrid iterative algorithm [Svidzinski et al., Phys. Plasmas 25, 082509 (2018)] for numerically solving discretized wave equations. This approach combines time evolution and iterative relaxation techniques into iteration cycles. This algorithm is implemented in 2D code FullWave, solving wave equations in Tokamaks in cold and hot plasma models, and it has been tested in 3D full wave iterative RF beams simulation tool, which is presently being developed to model 3D ECRH RF beams in fusion devices using dynamic grid adaptation. The results of 2D full wave modeling, assuming specified toroidal mode number, of ECRH RF beams in DIII-D plasma, performed in the cold and hot plasma models for outboard and top launch scenarios using FullWave are presented. Nonlocal hot plasma response model, based on accurate numerical solution of linearized Vlasov equation, is used to model beam propagation and absorption in the 2nd electron cyclotron harmonic region. Demonstration of capability of the hybrid iterative algorithm to model ECRH RF beams in 3D is made by simulating a substantial part of realistic beam in DIII-D, launched from outboard side of the machine. All relevant physics of RF beam propagation, most of which is not captured in paraxial approximation, such as beam's divergence, interference between the X and O modes in the beam, X-O mode conversion, beam splitting into the X and O mode beams, transformation of beam's cross section, and absorption at the 2nd electron cyclotron harmonic, is captured in the simulations. A numerical technique to find an optimal beam polarization at the launcher to launch a nearly pure X or O mode beam in plasma is developed and tested.

Inhomogeneous and nonlocal optical response in magic-angle twisted trilayer graphene

Inhomogeneous and nonlocal optical response in magic-angle twisted trilayer graphene

Nonlocal thermoelectric detection of interaction and correlations in edge states

Nonlocal thermoelectricity is proposed as a direct probe of interactions, nonthermal states, and the effect of correlations in the nonequilibrium heat transport between 1D quantum channels. In copropagating quantum Hall edge states contacted at different temperatures, the nonlocal thermoelectrical response is expected if the electron-electron interaction mediates the heat exchange directly measuring the interaction strength. Considering the low-energy limit of zero-range interactions, we analytically solve the charge and energy currents of a nonequilibrium interacting system, determining the universal scaling law in terms of an interaction-dependent energy-relaxation length. Further, a setup with two controllable quantum point contacts allows thermoelectricity to monitor the thermalization of an interacting system as well as the fundamental role of cross-correlations in the heat exchange at intermediate length scales. Published by the American Physical Society 2024

An Improved FDTD Method to Calculate Nonlocal Response in Plasmonics

An Improved FDTD Method to Calculate Nonlocal Response in Plasmonics