Chiral Parameter Research Articles

Transport phenomena in time-reversal symmetry-breaking Kagome superconductors

Recent studies have found that all three materials within the vanadium-based Kagome superconductors (<i>A</i>V<sub>3</sub>Sb<sub>5</sub>, <i>A</i> = K, Cs, Rb) exhibit time-reversal symmetry-breaking behaviors in the superconducting states. Among the three, the Josephson junctions structured Nb/K<sub>1–<i>x</i></sub>V<sub>3</sub>Sb<sub>5</sub>/Nb and RbV<sub>3</sub>Sb<sub>5</sub> show magnetic hysteresis below the superconducting transition temperature. In CsV<sub>3</sub>Sb<sub>5</sub>, there exists a zero-field superconducting diode effect, meaning the magnitude of the positive and negative superconducting critical current are different. We first discuss the similarities and differences among the three above-mentioned experiments. Then, we discuss the possible mechanisms responsible for the unconventional superconducting transport phenomena: such as chiral superconducting order parameter (d+id or p+ip), and chiral pair density waves arising from the coupling of the charge density waves and conventional superconducting states.

Microscopic origin of criticality at macroscale in QCD chiral phase transition

We reveal that the criticality of the chiral phase transition in QCD at the macroscale arises from the microscopic energy levels of its fundamental constituents, the quarks. We establish a novel relation between cumulants of the chiral order parameter (i.e., chiral condensate) and correlations among the energy levels of quarks (i.e., eigenspectra of the massless Dirac operator), which naturally leads to a generalization of the Banks-Casher relation. Based on this novel relation and through (2+1)-flavor lattice QCD calculations using the HISQ action with varying light quark masses in the vicinity of the chiral phase transition, we demonstrate that the correlations among the infrared part of the Dirac eigenspectra exhibit same universal scaling behaviors as expected of the cumulants of the chiral condensate. We find that these universal scaling behaviors extend up to the physical values of the up and down quark masses.

Chiral identification of lactic acid enantiomers by an achiral terahertz metasurface sensor

Lactic acid (LA) plays an essential role as a biochemical indicator in life, the detection and identification of chiral LAs have a wide range of applications. A method to detect chiral LA enantiomers (D-LA and L-LA) by using an achiral terahertz (THz) electromagnetically induced transparency (EIT) metasurface sensor is proposed. The chiral enantiomers of LA samples are measured, and the chiral parameters are extracted from the circular polarization transmission coefficients, theoretical analysis and experiment are combined to verify the principle of the achiral sensor to recognize the chiral LAs. The quantitative and qualitative recognition of LA enantiomers can be realized by the significant difference in the transmission spectrum at the characteristic frequency. The limit of detection reaches 0.01 μg/mL, and the sensing sensitivity of L-LA, D-LA, and DL-LA (achiral, racemate) is 0.28 THz/(mg/mL), 0.07 THz/(mg/mL) and 0.13 THz/(mg/mL), respectively. The proposed method can be further extended to a wide range of chiral bio-samples, showing a great potential in biomedical applications, food safety inspection, and environmental monitoring.

Analysis of the scattering of chiral layered particle by dual beams

The present study investigates the interaction between a chiral multilayer dielectric sphere and dual laser beams. Using the generalized Lorenz-Mie theory (GLMT), we extend the theory of single laser beam expansion to dual laser beam expansion. Analytical solutions of the scattering on chiral layered particles by dual laser beams are derived based on the boundary continuum condition. To validate the efficiency of our theory and methodologies proposed in this paper, we conduct a comparative analysis between our findings and the simulation results reported in existing literature. The numerical outcomes presented on the scattering pattern of far region and near-surface fields are analyzed in detail with the impact of various parameters, such as the incident angle, polarization angle, waist width, beam center position, inner and outer chiral parameters. The investigations are of significant importance for the analytical understanding of the optical scattering properties of multilayered biological cells with complex shapes and possess important application values in micro-manipulation of multilayered biological structures.

Features of backward waves and negative refraction in absorbing bi-isotropic media and metamaterials

ABSTRACT Conditions of the excitation of backward electromagnetic waves and negative refraction in absorbing bi-isotropic layered media and metamaterials are investigated. Based on the exact analytical model, the features determined by absorption and inhomogeneity of the waves and possible metamaterial properties of the medium are ascertained. It is shown that only simultaneous realization of backward, backward with respect to the boundary between two media, and negative refraction is possible for each of the proper waves in a bi-isotropic layer. The conditions are obtained when two (one transmitted and one reflected waves) or all the four proper waves in the layer are backward and characterized by negative refraction on boundaries. Taking into account the calculation of Pointing’s vector and energy dissipation of the waves, it is shown that the well-known limitations on the chirality and nonreciprocity parameters require a clarification for the considered media.

Analysis and Application of the Electromagnetic Wave Propagation, Fields, and Dispersion Relation in an Elliptical Chiro Plasma Waveguide Immersed in Magnetized Plasma

AbstractThis research proposes and investigates an elliptical waveguide filled with chiro plasma as its core and magnetized plasma as its clad region. The clad region is in the constant infinite magnetic field, and its direction is the same as the wave propagation in the chiro plasma elliptical waveguide. The electromagnetic wave propagation in the considered waveguide is studied. The expressions for electromagnetic field components in the chiro plasma core and magnetized plasma cladding are derived. The dispersion relations for the hybrid modes are calculated considering appropriate boundary conditions at the chiro plasma and magnetized plasma interface. The behavior of the energy flux and the dispersion curves are numerically and graphically studied. It is seen that the magnitude of the power density decreases with the increase of the cyclotron frequency and it increases with the increase of the plasma frequency and supports power flow in the backward direction for the considered mode. Furthermore, it is shown higher values of the chirality parameter cause the magnitude of the power flux to increase in the backward direction.

Chiral Metasurface Multifocal Lens in the Terahertz Band Based on Deep Learning.

Chiral metasurfaces have garnered significant interest as an emerging field of metamaterials, primarily due to their exceptional capability to manipulate phase distributions at interfaces. However, the on-demand design of chiral metasurface structures remains a challenging task. To address this challenge, this paper introduces a deep learning-based network model for rapid calculation of chiral metasurface structure parameters. The network achieves a mean absolute error (MAE) of 0.025 and enables the design of chiral metasurface structures with a circular dichroism (CD) of 0.41 at a frequency of 1.169 THz. By changing the phase of the chiral metasurface, it is possible to produce not only a monofocal lens but also a multifocal lens. Well-designed chiral metasurface lenses allow us to control the number and position of focal points of the light field. This chiral metasurface, designed using deep learning, demonstrates great multifocal focus characteristics and holds great potential for a wide range of applications in sensing and holography.

Optically Induced Symmetry Breaking Due to Nonequilibrium Steady State Formation in Charge Density Wave Material 1T-TiSe2.

The strongly correlated charge density wave (CDW) phase of 1T-TiSe2 is of interest to verify the claims of a chiral order parameter. Characterization of the symmetries of 1T-TiSe2 is critical to understand the origin of its intriguing properties. Here we use very low-power, continuous wave laser excitation to probe the symmetries of 1T-TiSe2 by using the circular photogalvanic effect. We observe that the ground state of the CDW phase (D3d) is achiral. However, laser excitation above a threshold intensity transforms 1T-TiSe2 into a nonequilibrium chiral phase (C3), which changes the electronic correlations in the material. The inherent sensitivity of the photogalvanic technique to structural symmetries provides evidence of the different optically driven phase of 1T-TiSe2, which allows us to assign symmetry groups to these states. Our work demonstrates that optically induced phase change can occur at extremely low optical intensities in strongly correlated materials, providing a pathway to engineer new phases using light.

Structural Description of Chiral E-Tiling DNA Nanotubes with the Chiral Indices (n,m) and Handedness Defined by Microscopic Imaging.

In structural DNA nanotechnology, E-tiling DNA nanotubes are evidenced to be homogeneous in diameter and thus have great potential in biomedical applications such as cellular transport and communication, transmembrane ion/molecule channeling, and drug delivery. However, a precise structural description of chiral DNA nanotubes with chiral parameters was lacking, thus greatly hindering their application breadth and depth, until we recently raised and partly solved this problem. In this perspective, we summarize recent progress in defining the chiral indices and handedness of E-tiling DNA nanotubes by microscopic imaging, especially atomic force microscopy (AFM) imaging. Such a detailed understanding of the chiral structures of E-tiling DNA nanotubes will be very helpful in the future, on the one hand for engineering DNA nanostructures precisely, and, on the other, for realizing specific physicochemical properties and biological functions successfully.

The abruptly autofocusing characteristics of the circular Airyprime beam in a chiral medium

In this paper, the abruptly autofocusing characteristics of the circular Airyprime beam (CAPB) propagating in a chiral medium is investigated for the first time. The results show that the CAPB splits into the left-handed circularly polarized (LCP) and the right-handed circularly polarized (RCP) beams with different propagating trajectories in the chiral medium. The focal length Zf, the depth of focal length Zw and the peak intensity of two focal field spots in the chiral medium can be effectively manipulated by the combination of initial beam parameters of CAPB (the primary ring radius r0, the scaling factor w0 and the exponential decay factor a) and the chiral medium parameter h. In addition, the expression of Zf derived from CAB can be well applied to CAPB. The Zf and the Zw of LCP and RCP components of CAPB and CAB are the same, but the autofocusing ability of CAPB is about 7 times of that of CAB under the same condition in the chiral medium, almost the same as that in free space. Due to the abruptly autofocusing ability and the propagation properties in a chiral medium, the CAPB may have potential applications in many fields such as biomedical treatment and optical manipulation.

Probing the QCD phase transition with hadron multiplicity ratios

We investigate the impact of a first-order chiral phase transition and critical point on hadron multiplicity ratios. We model the dynamical expansion of the hot and dense matter created in a heavy ion collision with a Bjorken hydrodynamics expansion coupled to the explicit evolution of the chiral order parameter at center-of-mass energies from 2 to 7 GeV. Hereby, the chiral dynamics is implemented using a Langevin equation including dissipation and noise. We find a strong enhancement of the entropy-per-baryon S/A at lowest energies which is created at the non-equilibrium first-order phase transition. By mapping the initial and final S/A to a hadron resonance gas, we can quantify the shift of hadron multiplicity ratios.

Gravity-induced dispersion in a chiral waveguide: transient regimes and imperfect temporal interfaces

The paper includes analysis of an elastic chiral waveguide, subjected to gravity, where a coupling between different displacement components is assumed owing to gyroscopic action. The importance of gravity and chirality on the dispersion of waves is demonstrated and behaviour in all regimes, including asymptotic ones, is addressed and linked to the value of the chirality parameter. In the transient regimes, we analyse chiral imperfect temporal interfaces in the waveguide subjected to gravity.

Enantioselective transport of chiral spheres using focused femtosecond laser pulses.

Optical tweezers are commonly used for manipulating chiral particles by tailoring the properties of the electromagnetic field or of the particles themselves. Non-linearity provides additional degree of freedom to control the manipulation by changing the trapping conditions. In this work, we leverage the nonlinear optical properties of a medium by illuminating it with a circularly polarized laser pulse, enabling single particle enantioselection for the chiral spheres immersed in it. By adjusting the power of the laser pulses, we demonstrate stable trapping of chiral spheres with one handedness near the focal region, while spheres with the opposite handedness are repelled. This enables the chiral resolution of racemic mixtures. Additionally, we perturbed the stable equilibrium position of the trap by driving the sample stage, leading to the emergence of a new stable equilibrium position achieved under the action of the Stokes force. Here we show that the chirality of each individually trapped particle can also be characterized by the rotation of the equilibrium position. Since the power of the laser pulses can be experimentally controlled, this scheme is practical to perform enantioselection, chiral characterization, and chiral resolution of a single chiral sphere with arbitrarily small chirality parameters.

Chiral superconductivity in the doped triangular-lattice Fermi-Hubbard model in two dimensions

The triangular-lattice Fermi-Hubbard model has been extensively investigated in the literature due to its connection to chiral spin states and unconventional superconductivity. Previous simulations of the ground state of the doped system rely on quasi-one-dimensional lattices where true long-range order is forbidden. Here we simulate two-dimensional and quasi-one-dimensional triangular lattices using state-of-the-art Auxiliary-Field Quantum Monte Carlo. Upon doping a non-magnetic chiral spin state, we observe evidence of chiral superconductivity supported by long-range order in Cooper-pair correlation and a finite value of the chiral order parameter. With this aim, we first locate the transition from the metallic to the non-magnetic insulating phase and the onset of magnetic order. Our results pave the way towards a better understanding of strongly correlated lattice systems with magnetic frustration.

Design of single-mode single-circularly polarized chiral anti-resonant fiber for the communication band

We propose a design of anti-resonant fiber (ARF) involving the introduction of chiral material into the inner regions of six germanium-doped silica glass cladding tubes, which can support the operation of single-mode single left-handed circular polarization in the communication band from 1.540 to 1.605 µm. In particular, the loss reaches a minimum value of 0.009 dB m−1 at 1.550 µm. The sign of the chiral parameter can control the handedness of polarization in the operation of single-mode single-circular polarization. In addition, the ARF possesses a good bending resistance performance. The minimum bending radius of the ARF is 10 to maintain the single-mode single left-handed circular polarization for 1.550 µm. We believe the novel ARF can find applications in optical communication, polarization imaging and chiral sensing.

Thermal Effects on Optical Chirality, Mechanics, and Associated Symmetry Properties

A review is provided here about the thermal effects on optical chirality. To this goal, chiral objects dispersed in an embedding fluid are examined for their magnetoelectric coupling. Thermal effects on several chiral meta-atoms and their ensembles are examined. To this goal, DNA-like helical structures are examined in detail. The mechanical aspect of thermo-elasticity is reviewed along with transverse deformations while drawing analogies from condensed-matter physics. In this respect, the chirality-induced spin selection is reviewed along with the temperature-mediated electron–phonon interactions. A wide range of materials, such as polymers and biological cells, are also examined for temperature effects. A transition temperature delineating a sign flip in the chirality parameter is identified as well. Chirality-associated functionalities such as ratchet motions, switching, and modulations are investigated for their respective thermal effects. Issues of fabricating chiral meta-atoms are also discussed.

Electromagnetic wave propagation in a chiroplasma-filled elliptical waveguide, bounded by a perfect electromagnetic conductor.

This work presents electromagnetic wave propagation in the elliptical waveguides filled with chiroplasma core and an outer perfect electromagnetic conductor boundary. The electromagnetic fields were theoretically examined. The hybrid modes' dispersion relations and power flux density were calculated considering appropriate boundary conditions, and their behaviors were numerically and graphically studied. The effects of the plasma frequency, the cyclotron frequency, the chirality parameter, and the perfect electromagnetic conductor admittance parameter were investigated for the cutoff frequency. Different modes were considered, and the dispersion relation was plotted and studied for each case. It was shown that the cutoff frequency changes with the change of various parameters such as the plasma and cyclotron frequencies, the chirality parameter, and the perfect electromagnetic conductor admittance parameter. In addition, it was shown that for the considered mode, when the plasma or cyclotron frequencies increase, the values of correspond cutoff frequencies have higher or lower values, respectively. Higher values of the perfect electromagnetic conductor admittance parameter or the chirality admittance parameter yield lower or higher cutoff frequencies of the modes, respectively.

Development of a mathematical model of a chiral metamaterial based on a cylindrical helical elements accounting for the dispersion and concentration of elements

Background. Interest in the study of microwave metamaterials is associated with the possibility of using them to achieve the required frequency and polarization selective properties of interaction with electromagnetic radiation, which can’t be obtained for structures based on homogeneous media. Aim. The mathematical model of a chiral metamaterial based on a periodic matrix of arbitrarily oriented conducting thin-wire cylindrical helices located in a homogeneous isotropic container creation is considered. Unlike known models, it takes into account the explicit form of the dependence of the effective permittivity and the relative chirality parameter on the helices concentration. Methods. The heterogeneity of a chiral metamaterial based on the Maxwell Garnett formula, which makes it possible to determine the effective dielectric permittivity from the permeabilities of the container and the region occupied by conducting mirror asymmetric inclusions is taken into account when creating a mathematical model. The dispersion of permittivity using the quadratic Lorentz formula and the dispersion of the chirality parameter based on the Condon model are taken into account. Results. Analytical frequency-dependent expressions for the effective permittivity and the chirality parameter taking into account the concentration of helices and their geometric parameters, were obtained in the work. The expression for the relationship between the dimensionless volume concentration of inclusions and the distance between adjacent elements is obtained. The quasi-static approach is used to calculate the resonant frequency of conducting thin-wire cylindrical helices. Conclusion. The proposed method for constructing a mathematical model can be applied to chiral metamaterials based on periodic matrices of conductive elements of an arbitrary mirror asymmetric spatial configuration.

Measurement of surface chirality at near-normal incidence

The chirality of a medium is typically measured either by transmitting a beam of light through it or by single or multiple interface reflection at large and/or special angles of incidence. We propose and demonstrate here the experimental measurement of surface chirality of z-cut quartz crystal by reflecting a focused beam of light at a near-normal angle of incidence. A small difference in the reflection coefficients between orthogonal elliptically polarized incident beam of 10−4 is measured in the dark-field region of the reflected light via the weak measurement method, taking advantage of the significant transverse spin-shift (TSS) that arises due to the interaction. The TSS behavior is simulated for different chiral parameters (±γ) of the material. The experimental results match well with the theoretically simulated behavior to quantify γ of quartz crystal used as an example interface. The significance of our method can be of interest for a wide variety of fundamental and applied investigations.

Can we still measure circular dichroism with circular dichroism spectrometers: The dangers of anisotropic artifacts.

Chiral materials with strong linear anisotropies are difficult to accurately characterize with circular dichroism (CD) because of artifactual contributions to their spectra from linear dichroism (LD) and birefringence (LB). Historically, researchers have used a second-order Taylor series expansion on the Mueller matrix to model the LDLB interaction effects on the spectra in conventional materials, but this approach may no longer be sufficient to account for the artifactual CD signals in emergent materials. In this work, we present an expression to model the measured CD using a third-order expansion, which introduces "pairwise interference" terms that, unlike the LDLB terms, cannot be averaged out of the signal. We find that the third-order pairwise interference terms can make noticeable contributions to the simulated CD spectra. Using numerical simulations of the measured CD across a broad range of linear and chiral anisotropy parameters, the LDLB interactions are most prominent in samples that have strong linear anisotropies (LD, LB) but negligible chiral anisotropies, where the measured CD strays from the chirality-induced CD by factors greater than 103 . Additionally, the pairwise interactions are most significant in systems with moderate-to-strong chiral and linear anisotropies, where the measured CD is inflated twofold, a figure that grows as linear anisotropies approach their maximum. In summary, media with moderate-to-strong linear anisotropy are in great danger of having their CD altered by these effects in subtle manners. This work highlights the significance of considering distortions in CD measurements through higher-order pairwise interference effects in highly anisotropic nanomaterials.