Right-handed States Research Articles

Generation of vectorial vortex beams by a coherently combined laser array

With the superpositions of spin and orbital angular momentum, vectorial vortex beams (VVBs) have attracted great attention in recent years. Many approaches have been developed to generate such beams, but high-power output is not supported. Here, we report the coherent beam combining (CBC) for generating VVBs that are compatible with high-power fiber amplifiers. The laser array is composed of two discrete vortex arrays with left-handed and right-handed circular polarization states. The phase and polarization of each beamlet are manipulated simultaneously. Experimentally, the phase noise in the amplifiers is compensated by the all-fiber internal phase control feedback structure. Quarter-wave plates are employed as polarization state converters. When the system is in the closed loop, a distinct and stable VVB can be obtained in the far-field. This work could provide a significant reference for the future implementation of high-power structured beams.

Zig-zag dynamics in a Stern–Gerlach spin measurement

The century-old Stern–Gerlach setup is paradigmatic for a quantum measurement. We visualize the electron trajectories following the Bohmian zig-zag dynamics. This dynamics was developed in order to deal with the fundamentally massless nature of particles (with mass emerging from the Brout–Englert–Higgs mechanism). The corresponding trajectories exhibit a stochastic zig-zagging, as the result of the coupling between left- and right-handed chiral Weyl states. This zig-zagging persists in the non-relativistic limit, which will be considered here, and which is described by the Pauli equation for a non-uniform external magnetic field. Our results clarify the different meanings of ‘spin’ as a property of the wave function and as a random variable in the Stern–Gerlach setup, and they illustrate the notion of effective collapse. We also examine the case of an EPR-pair. By letting one of the entangled particles pass through a Stern–Gerlach device, the non-local influence (action-at-a-distance) on the other particle is manifest in its trajectory, e.g. by initiating its zig-zagging.

Magnetic moments of astrophysical neutrinos

We study the impact of neutrino magnetic moments on astrophysical neutrinos, in particular supernova neutrinos and ultra-high energy neutrinos from extragalactic sources. We show that magnetic moment-induced conversion of Dirac neutrinos from left-handed states into unobservable right-handed singlet states can substantially change the flux and flavour composition of these neutrinos at Earth. Notably, neutrinos from a supernova's neutronisation burst, whose flux can be predicted with 𝒪(10%) accuracy, offer a discovery reach to neutrino magnetic moments ∼ few × 10-13 μB , up to one order of magnitude below current limits. For high-energy neutrinos from distant sources, for which no robust flux prediction exists, we show how the flavour composition at Earth can be used as a handle to establish the presence of non-negligible magnetic moments, potentially down to few× 10-17 μB if the measurement can be performed on neutrinos from a single source. In both cases, the sensitivity strongly depends on the galactic (intergalactic) magnetic field profiles along the line of sight. Therefore, while a discovery is possible down to very small values of the magnetic moment, the absence of a discovery does not imply an equally strong limit. We also comment on the dependence of our results on the right-handed neutrino mass, paying special attention to the transition from coherent deflection by a classical magnetic field to incoherent scattering on individual scattering targets. Finally, we show that a measurement of Standard Model Dirac neutrino magnetic moments, of order 10-19 μB , could be possible under rather optimistic, but not completely outrageous, assumptions using flavour ratios of high-energy astrophysical neutrinos.

A Solvable Algebra for Massless Fermions

We derive the stabiliser group of the four-vector, also known as Wigner’s little group, in case of massless particle states, as the maximal solvable subgroup of the proper orthochronous Lorentz group of dimension four, known as the Borel subgroup. In the absence of mass, particle states are disentangled into left- and right-handed chiral states, governed by the maximal solvable subgroups sol2± of order two. Induced Lorentz transformations are constructed and applied to general representations of particle states. Finally, in our conclusions, it is argued how the spin-flip contribution might be closely related to the occurrence of nonphysical spin operators.

Planar oligomerization of reconfigurable gold nanorod dimers.

Reconfigurable chiral plasmonic complexes are fabricated by planar assembly of multiple individual gold nanorod dimers using DNA origami templates. Additionally, each chiral center can be controlled to switch among achiral, left-handed, and right-handed states. We demonstrate that their overall circular dichroism is determined by the coupling of individual chiral centers and is heavily influenced by the precise number and arrangement of these centers. Our study offers a novel self-assembly method for constructing intricate and dynamic chiral plasmonics as well as investigating the interactions among several plasmonic chiral centers.

Optical-pumping enantio-conversion of chiral mixtures in presence of tunneling between chiral states

Enantio-conversion of chiral mixtures, converting the mixtures composed of left- and right-handed chiral molecules into the homochiral ensembles, has become an important research topic in chemical and biological fields. In previous studies on enantio-conversion, the tunneling interaction between the left- and right-handed chiral states was often neglected. However, for certain chiral molecules, this tunneling interaction is significant and cannot be ignored. Here we propose a scheme for enantio-conversion of chiral mixtures through optical pumping based on a four-level model of chiral molecules, comprising two chiral ground states and two achiral excited states, with a tunneling interaction between the chiral states. Under one-photon large detuning and two-photon resonance conditions, one of the achiral excited states is eliminated adiabatically. By well designing the detuning and coupling strengths of the electromagnetic fields, the tunneling interaction between two chiral states and the interaction between one of the chiral states and the remaining achiral excited state can be eliminated. Consequently, one chiral state remains unchanged, while the other can be excited to an achiral excited state, establishing chiral-state-selective excitations. By numerically calculating the populations of two chiral ground states and the enantiomeric excess, we observe that high-efficiency enantio-conversion is achieved under the combined effects of system dissipation and chiral-state-selective excitations.

Electroweak phase transition in a right-handed neutrino superfield extended NMSSM

Supersymmetric models with singlet extensions can accommodate single- or multi-step first-order phase transitions (FOPT) along the various constituent field directions. Such a framework can also produce Gravitational Waves, detectable at the upcoming space-based interferometers, e.g., U-DECIGO. We explore the dynamics of electroweak phase transition and the production of Gravitational Waves in an extended set-up of the Next-to-Minimal Supersymmetric Standard Model (NMSSM) with a Standard Model singlet right-handed neutrino superfield. We examine the role of the new parameters compared to NMSSM on the phase transition dynamics and observe that the occurrence of a FOPT, an essential requirement for Electroweak Baryogenesis, typically favours a right-handed sneutrino state below 125 GeV. Our investigation shows how the analysis can offer complementary probes for physics beyond the Standard Model besides the collider searches.

Switching Chirality in Arrays of Shape-Reconfigurable Spindle Microparticles.

The giant circular photo-galvanic effect is realized in chiral metals when illuminated by circularly polarized light. However, the structure itself is not switchable nor is the crystal chirality in the adjacent chiral domains. Here spindle-shaped liquid crystalline elastomer microparticles that can switch from prolate to spherical to oblate reversibly upon heating above the nematic to isotropic transition temperature are synthesized. When arranged in a honeycomb lattice, the continuous shape change of the microparticles leads to lattice reconfiguration, from a right-handed chiral state to an achiral one, then to a left-handed chiral state, without breaking the translational symmetry. Accordingly, the sign of rotation of the polarized light passing through the lattices changes as measured by time-domain terahertz spectroscopy. Further, it can locally alter the chirality in the adjacent domains using near-infrared light illumination. The reconfigurable chiral microarrays will allow us to explore non-trivial symmetry-protected transport modes of topological lattices at the light-matter interface. Specifically, the ability to controllably create chiral states at the boundary of the achiral/chiral domains will lead to rich structures emerging from the interplay of symmetry and topology.

Measurement of the polarisation of W bosons produced in top-quark decays using dilepton events at [formula omitted] TeV with the ATLAS experiment

A measurement of the polarisation of W bosons produced in top-quark decays is presented, using proton–proton collision data at a centre-of-mass energy of s=13 TeV. The data were collected by the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 139 fb−1. The measurement is performed selecting tt¯ events decaying into final states with two charged leptons (electrons or muons) and at least two b-tagged jets. The polarisation is extracted from the differential cross-section distribution of the cos⁡θ⁎ variable, where θ⁎ is the angle between the momentum direction of the charged lepton from the W boson decay and the reversed momentum direction of the b-quark from the top-quark decay, both calculated in the W boson rest frame. Parton-level results, corrected for the detector acceptance and resolution, are presented for the cos⁡θ⁎ angle. The measured fractions of longitudinal, left- and right-handed polarisation states are found to be f0=0.684±0.005(stat.)±0.014(syst.), fL=0.318±0.003(stat.)±0.008(syst.) and fR=−0.002±0.002(stat.)±0.014(syst.), in agreement with the Standard Model prediction.

Purification and CryoEM Image Analysis of the Bacterial Flagellar Filament.

The bacterial flagellum is a large assembly of about 30 different proteins and is divided into three parts: the filament that acts as a screw propeller, the hook as a universal joint, and the basal body as a rotary motor. In the case of Salmonella, the filament length is 10-15μm, which is more than ten times longer than the size of the cell. The filament is composed of only one component protein, flagellin, and is made of 11 protofilaments. The filament can form 12 different supercoiled structures as polymorphic forms. Each protofilament can take either the L (left-handed) or R (right-handed) state, and the number ratio of the protofilaments in these two states determines the shape of the supercoil. Some point mutations in flagellin make the filament straight by making all the protofilaments in one of the two states. The straight filaments enable us to use their helical symmetries for structural analysis by electron cryomicroscopy (cryoEM) and single particle image analysis. Here, we describe the methods for the purification of the flagellar filament and cryoEM data collection and image analysis.

A Polarization Reconfigurable 3D Printed Dual Integrated Quadrifilar Helix Antenna Array Embedded Within a Cylindrical Dielectric Mesh

This article presents a polarization reconfigurable dual integrated quadrifilar helix antenna array that is embedded within a cylindrical-shaped mesh of dielectric material. The entire structure is 3-D-printed and equipped with grooves to support the eight radiating elements and accordingly enforce the helical pitch and orientation. The dual antenna array, acting as one, features double fractional bandwidth (i.e., 30%) while exhibiting polarization reconfigurability by switching between left-handed and right-handed circular polarization states. More specifically, the proposed structure operates over the span of frequencies between 1.7 and 2.3 GHz while ensuring a circularly polarized behavior. The polarization reconfigurability is obtained by changing the phase excitation of the eight helical arms. Accordingly, a dedicated feeding network is proposed to achieve the required phase reconfiguration. A prototype is fabricated and tested as a proof of concept, where the measured results agree well with the simulated data. The 3-D-printed fabricated prototype reconfigures its circularly polarized behavior over the entire operating bandwidth with a maximum measured realized gain of 6.4 dBic, an axial ratio that varies between 0.5 and 2.5 dB, and cross-polarization levels of at least 20 dB along the direction of maximum radiation.

SM extension with a gauged flavor U(1)F symmetry

An extension of the Standard Model with anomaly free $U(1{)}_{F}$ flavor symmetry is studied in this paper. With this extension and the addition of the right-handed neutrino states, the solution of anomaly free charge assignments is found, which gives appealing texture zero and hierarchical Yukawa matrices. This gives us a natural understanding of the hierarchies between charged fermion masses and Cabibbo-Kobayashi-Maskawa matrix elements. Neutrino Dirac and Majorana coupling matrices also have desirable structures leading to successful neutrino oscillations with inverted neutrino mass ordering. Other interesting implications of the presented scenario are also discussed.

Sterile neutrinos, 0nu beta beta decay and the W-boson mass anomaly in a flipped SU(5) from F-theory

We investigate the low energy properties of an effective local model with flipped SU(5)times U(1)_{chi } gauge group, constructed within the framework of F-theory. Its origin is traced back to the SO(10) symmetry – associated with a geometric singularity of the compactification manifold – broken by an internal flux which is turned on along the seven-brane in the U(1)_{chi } direction. Topological properties and the choice of flux parameters determine the massless spectrum of the model to be that of the minimal flipped SU(5) supplemented with an extra right-handed electron-type state and its complex conjugate, E^c+{{bar{E}}}^c, as well as neutral singlet fields. The subsequent symmetry breaking to the SU(3)times SU(2)times U(1)_Y gauge group occurs with a Higgs pair in 10+{overline{10}} representations of SU(5). Next we proceed to the phenomenological analysis of the resulting effective model and the salient outcomes are: The E^c+{{bar{E}}}^c pair acquires a mass of few TeV and as such could solve the g_{mu }-2 discrepancy. Neutrino couplings to extra neutral singlets lead to an inverse seesaw mechanism where an extra light state could be a suitable dark matter candidate. The predictions of the model for the {0nu }beta beta decay rate could be tested in near future experiments. There are non-unitarity deviations from the lepton mixing matrix (U_{PMNS}), which could in principle explain the new precision measurement of the W-boson mass recently reported by the CDF II collaboration.

On chip chiral and plasmonic hybrid dimer or tetramer: Generic way to reverse longitudinal and lateral optical binding forces

For both the longitudinal binding force and the lateral binding force, a generic way of controlling the mutual attraction and repulsion (usually referred to as reversal of optical binding force) between chiral and plasmonic hybrid dimers or tetramers has not been reported so far. In this paper, by using a simple plane wave and an onchip configuration, we propose a possible generic way to control the binding force for such hybrid objects in both the near-field region and the far-field region. We also investigate different inter-particle distances while varying the wavelengths of light for each inter-particle distance throughout the investigations. First of all, for the case of longitudinal binding force, we find that chiral-plasmonic hybrid dimer pairs do not exhibit any reversal of optical binding force in the near-field region nor in the far-field region when the wavelength of light is varied in an air medium. However, when the same hybrid system of nanoparticles is placed over a plasmonic substrate, a possible chip, it is possible to achieve a reversal of the longitudinal optical binding force. Later, for the case of lateral optical binding force, we investigate a setup where we place the chiral and plasmonic tetramers on a plasmonic substrate by using two chiral nanoparticles and two plasmonic nanoparticles, with the setup illuminated by a circularly polarized plane wave. By applying the left-handed and the right-handed circular polarization state of light, we also observe the near-field and the far-field reversal of lateral optical binding force for both cases. As far as we know, so far, no work has been reported in the literature on the generic way of reversing the longitudinal optical binding force and the lateral optical binding force of such hybrid objects. Such a generic way of controlling optical binding forces can have important applications in different fields of science and technology in the near future.

Compact Augmented Reality Combiner Using Pancharatnam-Berry Phase Lens

A compact augmented reality (AR) combiner using Pancharatnam-Berry phase (PBP) lens and holographic optical element (HOE) is proposed. PBP lens is activated as a convex lens or a concave lens according to the polarization state of the input light wave. By using this characteristic, a thin AR eyepiece with a large numerical aperture (NA) is constructed. The AR eyepiece operates as a convex lens for the input light with a right-handed circular polarization state and operates as a transparent plate for the left-handed circularly polarized light. In order to adopt this AR eyepiece to the AR combiner, a chromatic aberration should be compensated. To resolve the chromatic aberration, HOE which diffracts the light rays with different profiles according to the input wavelength is designed. By combining this HOE with the AR eyepiece and a light guide, a compact AR combiner providing a wide field of view (FOV) is designed. A prototype of the proposed AR combiner is presented along with experimental results and analysis.

Reconfigurable Plasmonic Diastereomers Assembled by DNA Origami.

Herein, we report self-assembled reconfigurable plasmonic diastereomers based on DNA nanotechnology. Up to three plasmonic chiral centers were organized by dynamic DNA origami platforms. Meanwhile, each chiral center could be individually controlled to switch between left-handed and right-handed states. Thus, complex and reconfigurable chiral plasmonic diastereomers with eight plasmonic stereoisomers were achieved, driven by programmed DNA reactions. With these plasmonic diastereomers, we demonstrated the existence of strong cross-talk near-field coupling among chiral centers, and the coupling of chiral centers could substantially contribute to the overall CD signals. Our work provides an important bottom-up approach for building complex and dynamic chiral plasmonics and for probing the interactions of plasmonic chiral centers.

Polarization controllable generation of flat superimposed OAM states based on metasurface.

In this paper, two kind of metasurface-based flat orbital angular momentum (OAM) superposition-state generators are proposed, which can generate OAM superposition states possessing tens of OAM modes being evenly spaced by topological charge number 1. The power spectra of the generated OAM superposition states are flat. The power variation of the OAM modes of the OAM superposition states from one generator is less than 3 dB, and the power variation of the OAM modes of the OAM superposition states from the other one is less than 0.3 dB. By controlling the left-handed and right-handed circular polarization states of the incident light, the OAM spectra of the OAM superposition states generated in the two polarization cases are separated from each other, therefore, the proposed generators are light polarization controllable. In addition, the two generators can operate efficiently on a wide wavelength region ranging from 635nm to 730nm. Our work may have some potential applications, such as used for OAM multicasting, OAM based optical manipulation, or manufacturing integrated OAM-superposition-state generators and OAM modulation devices.

A well-balanced numerical scheme for a model of two-phase flows with treatment of nonconservative terms

We construct a numerical scheme for a model of two-phase flows. The keystone is the treatment of nonconservative terms using stationary contact discontinuities. The nonconservative terms are absorbed into left-hand and right-hand states of the local stationary contact discontinuity at each grid node. The numerical scheme is built by taking into accounts the states on both sides of local contact discontinuities as supplemented facts of a standard numerical approximation for the conservative part of the system. The scheme is shown to possess interesting properties: it preserves the positivity of the volume fractions in both phases and the positivity of the gas density, it is well-balanced and satisfying the numerical minimum entropy principle in the gas phase.

Nonreciprocal superposition state in antiferromagnetic optospintronics

The absence of net magnetization, which forbids any stray magnetic fields, is one of the greatest advantages of antiferromagnets in device applications. In conventional antiferromagnets, however, spin current cannot be extracted without the aid of a static magnetic field. Here, we develop a theory of antiferromagnetic opto-spintronics to resolve this fundamental dilemma. By coupling a linearly polarized photon and nonreciprocal magnon bands, we construct a superposition state of left- and right-handed magnon states with opposite group velocities. We numerically demonstrate that by using this superposition state, an antiferromagnetic spin current can be efficiently generated without a net magnetic field including net magnetization. We also find that the breakdown of the superposition state induces the stripe superfluid phase of a two-component Bose-Einstein condensate. Our results lay the foundation for manipulating the superposition states of emergent particles in devices.

Terahertz wire-grid circular polarizer tuned by lock-in detection method.

We report the design, construction, and testing of a broadband-tunable terahertz circular polarizer, which we developed for our magneto-optical measurements using the far-infrared/THz laser source in the range of 0.25-7.5 THz. We present a thorough analysis of the lock-in amplifier signal generated by using a rotating analyzer with regard to setting the desired state of polarization. The phase-sensitive detection method is applied to a combination of a wire-grid polarizer and a parallel translation mirror providing a tunable retardance. The proposed technique is appropriate not only to free-standing grids but also to those deposited on transparent substrates which may introduce additional non-linear effects. The method is preferred when the distance between the mirror and the grid cannot be exactly determined, but the relative displacements are measured. The device enables switching between left- and right-handed polarization states on a time scale of a few seconds. Practical use of the circular polarizer is demonstrated by directly probing the far infra-red magneto-optical properties of the two-dimensional electron gas on the 458 μm laser line.