Chiral Parameter Research Articles

Electromagnetic wave propagation in time-periodic chiral media

Within the framework of coupled-wave theory, we investigate the propagation of light in a time-periodic chiral medium whose permittivity, permeability, and chirality parameter are periodic functions of time. For non-constant impedance, we show that two first-order momentum gaps emerge in the Brillouin diagram, resulting in parametric amplification with distinct amplification factors and corresponding momenta for right- and left-handed modes. The presence of chirality plays a pivotal role in manipulating lightwave signals, controlling the center of resonance, the corresponding bandgap size, and the amplification factor in a unique manner for each handedness. For a finite “time-slab” of the considered medium, we analytically derive the scattering coefficients as functions of both time and momentum. Additionally, we discuss how extreme values of optical rotation grant access to the temporal analog of the chirality-induced negative refraction regime. Finally, we elucidate the mechanism by which the orientation of the electric field, associated with elliptical polarizations, is altered as the wave propagates within a first-order momentum gap, thereby undergoing simultaneous optical rotation and parametric amplification.

Transmission of an optical wave through a multilayer structure with dispersive chiral layers

Background. The using of mirror asymmetric chemical compounds for doping quartz makes it possible to metamaterial creation that has the chirality property. In such a compositional structure, unusual effects may arise when interacting with an optical wave. Aim. We calculate the transmission and reflection of a linearly polarized optical wave through a multilayer structure consisting of two doped quartz glasses separated by two air gaps. Methods. Based on a homogeneous mathematical model of a chiral metamaterial, taking into account the dispersion of the dielectric constant and the chirality parameter based on the matrix method, a system of linear algebraic equations is obtained for the complex reflection and transmission coefficients of an electromagnetic wave of linear polarization. Results. An analysis of the frequency and angular characteristics of the modules of the reflection and transmission coefficients was carried out at various values of the quartz doping level. It is theoretically predicted that at some wavelengths, most of the incident optical energy can be concentrated in the air gaps of the multilayer structure. Conclusion. The data obtained as a result of calculations can be used in the development of planar structures for frequency-selective concentration of energy in the visible and infrared spectrum based on quartz glasses doped with chiral chemical compounds.

Broadband spin-dependent anti-reflection in chiral time-varying metamaterials.

Time-varying metamaterials have garnered significant attention for their ability to achieve anti-reflection in the time domain. However, current systems face limitations in spin-controlled manipulation, as most studies focus on non-chiral, time-varying metamaterials. Consequently, realizing spin-dependent broadband anti-reflection using time-varying chiral metamaterials remains underexplored. In this work, we propose a time-varying chiral structure composed of four temporal layers, each with distinct impedances and chiral parameters. By carefully adjusting these parameters across the layers, our structure enables broadband anti-reflection for both right- and left-circularly polarized (RCP and LCP) waves under small chiral conditions. Under large chiral parameters, the structure selectively achieves broadband anti-reflection for LCP waves, while consistently reflecting RCP waves across the bandwidth. This unique spin-dependent broadband anti-reflection results from significant phase delays between RCP and LCP waves, a feature not achievable by non-chiral, time-varying multilayer structures. Additionally, the proposed structure allows impedance matching between chiral and non-chiral dielectric spatial-temporal slabs in finite regions under small chiral parameters. These findings offer promising avenues for advanced wave manipulation in chiral metamaterials, with potential applications in broadband absorbers, filters, and quantum information processing systems.

Propagation of spatiotemporal Airy-Laguerre complex-variable-function Gaussian wave packets in a chiral medium

We analyze the propagation of spatiotemporal Airy-Laguerre complex-variable-function Gaussian (ALCG) wave packets using phase modulation. These wave packets can split into left circularly polarized ALCG (LCP-ALCG) and right circularly polarized ALCG (RCP-ALCG) components due to circular birefringence in a chiral medium. Our discussion primarily focuses on the effects of polynomial order, angle parameters, distribution factor, cross-phase factor, first-order chirp factor, and chiral parameter on the ALCG wave packets. The distinct LCP-ALCG and RCP-ALCG wave packet characteristics are obtained, and the radiation forces on Rayleigh dielectric particles are investigated. Our results emphasize the influence of various parameters in the propagation properties of ALCG wave packets, unveiling their potential for advancements in optical communication and optical trapping domains.

Singular photon spin Hall effect in chiral-graphene heterostructures and its application in chirality detection.

In this paper, we consider the singular photonic spin Hall effect (PSHE) in a chiral-graphene-chiral (CGC) heterostructure in the THz band. We investigate the impact of a chiral medium on reflectance spectra and the modulation of the Fermi energy on the surface conductivity of graphene. Our study shows that placing a chiral medium on both sides of a monolayer of graphene results in an enhanced transverse shift (TS) compared to placing a non-chiral medium. Moreover, the direction of the TS of the PSHE can be altered by adjusting the sign of the chirality parameter and the Fermi energy of graphene. Finally, we establish a quantitative relationship between the PSHE and the chirality parameter and the Fermi energy of graphene. By dynamically modulating the PSHE in graphene, it is possible to flexibly detect chirality parameters. This work opens up new avenues for chiral molecular detection and graphene-PSHE dynamic modulation.

Multidimensional dynamic control of optical skyrmions in graphene–chiral–graphene multilayers

Abstract Optical skyrmions are topological quasiparticles with a complex vectorial field structure. Their associated characteristics of ultra-small, ultra-fast and topological protection have great application prospects in high density data storage, light matter interaction and optical communication. At present, the research of optical skyrmions is still in its infancy, where the construction and flexible regulation of different topological textures are current research hotspot. Here, we combine the twist degree of freedom of materials and optical skyrmions. Based on graphene–chiral–graphene multilayers structure, we demonstrate the field mode symmetry and hybridization to form Bloch-type graphene plasmons skyrmion lattice. At the same time, by changing chirality parameter, the Fermi energy of graphene and the phase of incident light, multidimensional control of Bloch-type optical skyrmions can be realized. Our work demonstrated that the properties of materials provide the additional dimensions to regulate the topological states, and the combination of different materials structures provides the possibility for dynamic construction and manipulation of multiple topological states, which is expected to find applications in integrated nanophotonics devices.

Longitudinal chiral forces in photonic integrated waveguides to separate particles with realistically small chirality

Abstract Chiral optical forces exhibit opposite signs for the two enantiomeric versions of a chiral molecule or particle. If large enough, these forces might be able to separate enantiomers all optically, which would find numerous applications in different fields, from pharmacology to chemistry. Longitudinal chiral forces are especially promising for tackling the challenging scenario of separating particles of realistically small chiralities. In this work, we study the longitudinal chiral forces arising in dielectric integrated waveguides when the quasi-TE and quasi-TM modes are combined as well as their application to separate absorbing and non-absorbing chiral particles. We show that chiral gradient forces dominate in the scenario of beating of non-denegerate TE and TM modes when considering non-absorbing particles. For absorbing particles, the superposition of degenerate TE and TM modes can lead to chiral forces that are kept along the whole waveguide length. We accompany the calculations of the forces with particle tracking simulations for specific radii and chirality parameters. We show that longitudinal forces can separate non-absorbing chiral nanoparticles in water even for relatively low values of the particle chirality and absorbing particles with arbitrarily low values of chirality can be effectively separated after enough interaction time.

Odd-Even Law Mediated Supramolecular Chirality of Luminescent Dipeptides for Chiroptical Energy Transfer.

Inherent luminescent short peptides essentially provide opportunities to rationally manipulate supramolecular chirality and chiral luminescence. Herein, a facile protocol to construct a series of naphthalimide-appended dipeptides is reported that show ultrasound wave-activated supramolecular chirality regulated by odd-even law. Naphthalimide luminophores are conjugated to the dipeptide skeleton with variable alkyl spacers. The presence of tyrosine interferes the kinetic aggregation into achiral nanoparticles without chirality transfer to supramolecular scale. However, ultrasound treatment initiates the nanoparticle-to-helix transition accompanied with the appeared chiral optics, including Cotton effect and circularly polarized luminescence (CPL). The supramolecular chiral parameters, including handedness of helices and chiroptical behaviors, follow the odd-even law of alkyl spacers in dipeptides bearing non-substituted naphthalimides. The amine-substitution boosted the quantum yields of dipeptide whereas no odd-even effect. The two types of dipeptides constituted ideal energy transfer pairs that enable the efficient energy transfer as well as the transportation of odd-even law to dipeptides containing substituted naphthalimides. This work sheds light on the construction of luminescent dipeptides with applications in precise control over chirality transportation and chiral luminescence.

Tunable polarization-dependent defect modes and lateral shifts of one-dimensional photonic crystals containing Dirac semimetal-based hyperbolic metamaterials and chiral materials

The transmission and lateral shift properties of the one-dimensional photonic crystals containing Dirac semimetal-based hyperbolic metamaterials and chiral material defects are theoretically investigated by using the transfer matrix method in terahertz. It is found that the angle-independent omnidirectional photonic bandgaps (PBGs) for p-polarization can be realized in the photonic crystals made of dielectric and the Dirac semimetal-based hyperbolic metamaterials. However, the PBGs are blue-shifted with the incident angle for s-polarized wave. The omnidirectional PBGs can be tunable with the Fermi energy of the Dirac semimetal, the thickness ratio of the constitute layers and the structural parameters. When one or two isotropic chiral material layers are introduced in the photonic crystals, double or four polarization-dependent defect modes are found in the bandgap under oblique incidence due to the coupling and conversion between different polarized waves in the chiral defects. The frequency interval of the defect modes changes with the chirality parameter and the incident angle. It is also found that when a light is incident on the defective photonic crystals, the giant positive and negative Goos-Hänchen shifts of co-polarization reflected waves can be induced around the defect modes, which are sensitive to the polarization, the incident angle, the incident frequency and the chirality. The special optical properties of the proposed defective multiplayers provide possibilities for practical applications in designing polarization sensitive optical devices, such as filter and sensor.

Using the dispersion model of a chiral metamaterial to calculate the characteristics of homogeneous and heterogeneous reflective and waveguide structures

Currently, metamaterials are actively used in the creation of microwave and optic devices for various purposes. This is due to their non-traditional properties, compared to dielectric, conductive and other materials. One type of metamaterial is chiral media, which contain conductive microelements of mirror asymmetric shape. Such metamaterials have dispersion and, as a consequence, it is necessary to take it into account when developing various microwave structures. The work demonstrates taking into account the dispersion of the dielectric constant and the chirality parameter for calculating waveguide and reflecting structures with homogeneous and inhomogeneous chiral layers. The work carried out an electrodynamic analysis of the reflective properties of an inhomogeneous chiral layer and a rectangular waveguide, with a homogeneous layer of chiral metamaterial located in the transverse plane. The work has developed a method for calculating the reflection and transmission coefficients of an optical wave from the inhomogeneous chiral structure under consideration, which is based on the use of the differential sweep method. When constructing a mathematical model, we took into account the cross-polarization of the optical wave field, which consists in the appearance of orthogonal components during the interaction of the field with a chiral metamaterial. The solution to the problem was reduced to a matrix differential equation for the unknown reflection coefficients of the main and cross-polarized components of the optical field. The work examined chiral metamaterials with linear and parabolic inhomogeneity profiles. The results of the work can be applied in the design of new microwave and optics devices with layers of metamaterial, which can expand their functionality.

Variational MonteCarlo Study of the 1/9-Magnetization Plateau in Kagome Antiferromagnets.

Motivated by very recent experimental observations of the 1/9-magnetization plateaus in YCu_{3}(OH)_{6+x}Br_{3-x} and YCu_{3}(OD)_{6+x}Br_{3-x}, our study delves into the magnetic-field-induced phase transitions in the nearest-neighbor antiferromagnetic Heisenberg model on the kagome lattice using the variational MonteCarlo technique. We uncover a phase transition from a zero-field Dirac spin liquid to a field-induced magnetically disordered phase that exhibits the 1/9-magnetization plateau. Through a comprehensive analysis encompassing the magnetization distribution, spin correlations, chiral order parameter, topological entanglement entropy, ground-state degeneracy, Chern number, and excitation spectrum, we pinpoint the phase associated with this magnetization plateau as a chiral Z_{3} topological quantum spin liquid and elucidate its diverse physical properties.

Baryogenesis via QCD preheating with nonadiabatic baryon chemical potential

The chiral phase transition in QCD can be supercooled in the thermal history of the universe to be instantaneously out-of equilibrium, if QCD is coupled to a dark QCD sector exhibiting the dark chiral phase transition of the first order. In that case the QCD sigma meson field (as the chiral order parameter, or the light quark condensate) starts to roll in a nonadiabatic way down to the true QCD vacuum. Meanwhile a dynamic baryonic chemical potential can be generated solely within QCD, which is governed by the dynamic motion of the QCD sigma meson field, analogously to the spontaneous baryogenesis or the leptogenesis via the Higgs or axionlike relaxation scenario. When QCD is further allowed to communicate with a dark fermion with mass of order of 1 GeV and the baryon number violating coupling to neutron, the nonadiabatic QCD sigma motion along with the nonadiabatic baryon chemical potential can trigger the preheating and produce the baryon number asymmetry. We discuss this scenario in details to find that the QCD-induced dynamic baryon chemical potential plays a significant role for the QCD preheating and the baryogenesis, which yields the desired amount of the asymmetry today consistently with current astrophysical, cosmological, and terrestrial experimental constraints. Cosmological and phenomenological consequences characteristic to the present scenario are also addressed.

Chirality identification of Ibuprofen enantiomers by a terahertz polarization-sensitive metasurface sensor

Chirality plays an important role in medicine, biology, and chemistry. Molecules of different chirality could display dramatically different medical effects, pharmacological activities, and physiological impacts. Ibuprofen is an important anti-inflammatory drug in clinics. The anti-inflammatory effect is almost solely attributed to the (S)-(+)-Ibuprofen, while its enantiomer (R)-(-)-Ibuprofen plays a negative effect on increasing the metabolic burden. In this work, a terahertz (THz) polarization-sensitive metasurface sensor is proposed for qualitative and quantitative identification of the chiral Ibuprofen. The chirality parameters of Ibuprofen are extracted from the circular-polarized transmission coefficients. The parameters are further used to simulate the coupling mechanism between the Ibuprofen and the sensor to explain the principle of recognition. The sensitivities of (R)-(-)-Ibuprofen and (S)-(+)-Ibuprofen are found to be 1.5 THz/(mg/L) and 1.8 THz/(mg/L) for the TM polarization, respectively, and 1.7 THz/(mg/L) and 2.1 THz/(mg/L) for the TE polarization, respectively. The difference enables the chirality identification according to the different frequency shift at the same concentration. The exceptional specificity and sensitivity provide a new avenue for chiral molecular recognition.

Hyper-Rayleigh Scattering and Third-Harmonic Scattering in Chiral Liquids: Basic Evidences and Differences with Linear Chiroptical Techniques.

Nonlinear chiroptical methods like hyper-Rayleigh optical activity (HROA) and third-harmonic optical activity (THOA) have a great potential in characterizing structure-chiroptical properties of molecular systems. Here, with these methods, we bring for the first time experimental and theoretical evidence of nonlinear chiroptical differences between enantiomers of simple chiral molecules, using exclusively linearly polarized incident light. The origin of these unexpected nonlinear chiroptical contributions comes from a new nonlinear source term of the form βOA(∇×μ(nω)), which is a bilinear coupling term including the linear chirality parameter, βOA, and the curl of the nonlinear induced electric dipole moment, μ(nω), both involving dipolar magnetic interactions. Through a simple nonlinear chiroptical model that we propose, we show that specific nonlinear chiroptical parameters can be quantified, thus bringing new insights into stereochemical and electronic structural features of molecular and supramolecular systems.

Scattering properties of dual Bessel beams on chiral layered particle

The paper investigates the scattering analytical solution of arbitrary direction double zero-order Bessel beams (ZOBBs) incident on a non-uniform layered chiral sphere. Using the generalized Lorenz-Mie theory (GLMT), the electromagnetic field expansion expression of the double ZOBBs is obtained through the vector superposition of the spherical vector wave functions (SVWFs). Analytical solutions of the scattering on chiral layered particles by dual Bessel beams are derived based on the boundary condition. The iterative coefficient equations are constructed to obtain the expansion coefficients of the SVWFs in each region of the multi-layer chiral sphere. The variation of radar cross section (RCS) with angular distribution is numerically simulated, and the scattering results of layered chiral spheres degenerated into isotropic layered spheres are compared with the literature, which verifies the correctness of the theory and program. The effects of incident angle, polarization angle, cone angle and chiral parameters on the scattering characteristics of far region and internal field of the layered chiral particle are analyzed in detail. The theory and results can offer significant assistance in studying the optical properties of non-uniform chiral particles and complex biological cells irradiated by multiple beams and may also provide important practical value in the micromanipulation of multi-layered biological structures.

Anomalous Hall effects in chiral superconductors

We report theoretical results for the electronic contribution to thermal and electrical transport for chiral superconductors belonging to even or odd-parity E1 and E2 representations of the tetragonal and hexagonal point groups. Chiral superconductors exhibit novel properties that depend on the topology of the order parameter and Fermi surface, and—as we highlight—the structure of the impurity potential. An anomalous thermal Hall effect is predicted and shown to be sensitive to the winding number, ν, of the chiral order parameter via Andreev scattering that transfers angular momentum from the chiral condensate to excitations that scatter off the random potential. For heat transport in a chiral superconductor with isotropic impurity scattering, i.e., point-like impurities, a transverse heat current is obtained for ν = ±1, but vanishes for |ν| > 1. This is not a universal result. For finite-size impurities with radii of order or greater than the Fermi wavelength, R ≥ ℏ/pf, the thermal Hall conductivity is finite for chiral order with |ν|≥ 2, and determined by a specific Fermi-surface average of the differential cross-section for electron-impurity scattering. Our results also provide quantitative formulae for analyzing and interpreting thermal transport measurements for superconductors predicted to exhibit broken time-reversal and mirror symmetries.

Critical Opalescence and Its Impact on the Jet Quenching Parameter q^

Jet quenching parameter q^ is essential for characterizing the interaction strength between jet partons and nuclear matter. Based on the quark-meson model, we develop a new framework for calculating q^ at finite chemical potentials, in which q^ is related to the spectral function of the chiral order parameter. A mean field perturbative calculation up to the one-loop order indicates that the momentum broadening of jets is enhanced at both high temperature and high chemical potential, and approximately proportional to the parton number density in the partonic phase. We further investigate the behavior of q^ in the vicinity of the critical endpoint (CEP) by coupling our calculation with a recently developed equation of state that includes a CEP in the universality class of the Ising model, from which we discover the partonic critical opalescence, i.e., the divergence of scattering rate of jets and their momentum broadening at the CEP, contributed by scatterings via the σ exchange process. Hence, for the first time, jet quenching is connected with the search of CEP.

Phase structure of the on-shell parametrized 2+1 flavor Polyakov quark-meson model

Augmenting the improved chiral effective potential of the on-shell renormalized 2+1 flavor quark-meson (RQM) model with the Polyakov-loop potential that accounts for the deconfinement transition, we get the quantum chromodynamics (QCD)-like framework of the renormalized Polyakov quark-meson (RPQM) model. When the divergent quark one-loop vacuum term is included in the effective potential of the quark-meson (QM) model, its tree-level parameters, or the parameters fixed by the use of meson curvature masses, become inconsistent as the curvature masses involve the self-energy evaluations at zero momentum. Using the modified minimal subtraction method, the consistent chiral effective potential for the RQM model has been calculated after relating the counterterms in the on-shell scheme to those in the MS¯ scheme and finding the relations between the renormalized parameters of both the schemes where the physical (pole) masses of the π, K, η, and η′ pseudoscalar mesons and the scalar σ meson, the pion and kaon decay constants, have been put into the relation of the running couplings and mass parameter. Using the RPQM model and the PQM model with different forms for the Polyakov-loop potentials in the presence or the absence of the quark backreaction, we have computed and compared the effect of the consistent quark one-loop correction and the quark backreaction on the scaled chiral order parameter, the QCD phase diagrams, and the different thermodynamic quantities. The results have been compared with the 2+1 flavor lattice QCD data from the Wuppertal-Budapest Collaboration [ 73, ] and the HotQCD Collaboration []. Published by the American Physical Society 2024

Two-component nematic superconductivity in 4Hb-TaS2

Most superconductors have an isotropic, single component order parameter and are well described by the standard (BCS) theory for superconductivity. Unconventional, multiple-component superconductors are exceptionally rare and are much less understood. Here, we combine scanning tunneling microscopy and angle-resolved macroscopic transport for studying the candidate chiral superconductor, 4Hb-TaS2. We reveal quasi-periodic one-dimensional modulations in the tunneling conductance accompanied by two-fold symmetric superconducting critical field. The strong modulation of the in-plane critical field, Hc2, points to a nematic, unconventional order parameter. However, the imaged vortex core is isotropic at low temperatures. We suggest a model that reconciles this apparent discrepancy and takes into account previously observed spontaneous time-reversal symmetry breaking at low temperatures. The model describes a competition between a dominating chiral superconducting order parameter and a nematic one. The latter emerges close to the normal phase. Our results strongly support the existence of two-component superconductivity in 4Hb-TaS2 and can provide valuable insights into other systems with coexistent charge order and superconductivity.

Drastic magnetic-field-induced chiral current order and emergent current-bond-field interplay in kagome metals.

In kagome metals, the chiral current order parameter [Formula: see text] with time-reversal-symmetry-breaking is the source of various exotic electronic states, while the method of controlling the current order and its interplay with the star-of-David bond order [Formula: see text] are still unsolved. Here, we reveal that tiny uniform orbital magnetization [Formula: see text] is induced by the chiral current order, and its magnitude is prominently enlarged under the presence of the bond order. Importantly, we derive the magnetic-field ([Formula: see text])-induced Ginzburg-Landau (GL) free energy expression [Formula: see text], which enables us to elucidate the field-induced current-bond phase transitions in kagome metals. The emergent current-bond-[Formula: see text] trilinear coupling term in the free energy, [Formula: see text], naturally explains the characteristic magnetic-field sensitive electronic states in kagome metals, such as the field-induced current order and the strong interplay between the bond and current orders. The GL coefficients of [Formula: see text] derived from the realistic multiorbital model are appropriate to explain various experiments. Furthermore, we discuss the field-induced loop current orders in the square lattice models that have been studied in cuprate superconductors.