Transverse Spin Research Articles

Method to quickly estimate T1 value by suppressing spin exchange relaxation and magnetic field gradient relaxation in atomic sensors

The accuracy of atomic sensor is determined by the transverse nuclear spin relaxation time (T2). As the longitudinal nuclear spin relaxation time (T1) is the upper limit of T2, it becomes an important metric for evaluating the merits of alkali vapor cells. However, the conventional method for measuring T1 of pulse delay takes dozens of minutes, which will increase the effect of random errors during the testing process. In order to solve this problem, a method to quickly estimate the value of T1 is proposed by suppressing the influence of spin exchange relaxation and magnetic field gradient relaxation terms on T2. Experimental results indicate that the accuracy is maintained at above 95%, and the testing time is reduced to less than 5%.

Energy-resolved spin correlation measurements: Decoding transverse spin dynamics in weakly interacting Fermi gases

Energy-resolved spin correlation measurements: Decoding transverse spin dynamics in weakly interacting Fermi gases

Generation of pure transverse spin and nontrivial polarization structures of beams by dielectric metasurface

Transverse spin, a spin component with unique characteristics, provides a new dimension for plenty of applications, such as optical trapping, imaging, and communication. Here, we analyze the pure transverse spin in the Bessel beam, which is solely present in the azimuthal direction. Based on a single layer dielectric metasurface, we efficiently generate Bessel beams with pure transverse spin in a compact optical system. As designed, the transverse spin is flexibly tunable by converting the polarization of the incident light. Furthermore, in the scattered Bessel beam, the local electromagnetic field oscillates around the transverse axis, which is perpendicular to the beam propagation. At certain positions, the local polarization ellipse degenerates into a perfect circle, resulting in a ring-periodic distribution of circularly polarized points (C points) in the beam. This suggests that the local polarization demonstrates a nontrivial periodic structure. This work deepens our understanding of spin-related physics and opens a new avenue for the study and application of transverse spins in ultracompact, flat, multifunctional nanophotonic platforms.

On-chip optical wavefront shaping by transverse-spin-induced Pancharatanam-Berry phase.

Pancharatnam-Berry (PB) metasurfaces can be applied to manipulate the phase and polarization of light within subwavelength thickness. The underlying mechanism is attributed to the geometric phase originating from the longitudinal spin of light. Here, we demonstrate, to the best of our knowledge, a new type of PB geometric phase derived from the intrinsic transverse spin of guided light. Using full-wave numerical simulations, we show that the rotation of a metallic nano-bar sitting on a metal substrate can induce a geometric phase covering 2π full range for the surface plasmons carrying an intrinsic transverse spin. Especially, the geometric phase is different for the surface plasmons propagating in opposite directions due to spin-momentum locking. We apply the geometric phase to design metasurfaces to manipulate the wavefront of surface plasmons to achieve steering and focusing. Our work provides a new mechanism for on-chip light manipulations with potential applications in designing ultra-compact optical devices for imaging and sensing.

Tight focusing of the vector optical field with polarization varying along complex curves of the Poincaré sphere.

Different from the scalar optical field with spatially uniform polarization, the vector optical field exhibits inhomogeneous distribution of polarization on the cross section. Manipulating the variation of polarization in a single optical beam is important to acquire a flexible and controllable focused optical field. Previous studies mainly focused on the vector optical field with its polarization varying along a circular trajectory of the Poincaré sphere. Here, we demonstrate the tight focusing behaviors of the vector optical field with the polarization varying along complex curves of the Poincaré sphere, which is generated by the joint modulation of azimuthal phase and amplitude distributions of orthogonally polarized components. The longitudinal polarization component with a multipolar pattern in rotational symmetry can be achieved with similar distribution of the total focused field. The transverse and longitudinal spin angular momentum distributions in the focal space are discussed. Approximately pure transverse spin angular momentum can be constructed and manipulated in the focal space, which provides the possibility to manipulate the 3D spin flux for the applications of nano and spin photonics.

Quantum phase transitions in the alternating XY chain with three-site interactions

We investigate the quantum phase transition in the alternating XY chain with the XZY+YZX type of three-spin interactions. We present the exact solution derived by means of the Jordan–Wigner transformation and study the average magnetization, spin correlations, and von Neumann entropy to establish the phase diagram. The phase diagram consists of the ferromagnetic phases, the paramagnetic phases, and the phase with weak magnetization (WM). By examining the nearest-neighbor transverse spin correlation, we probe that in the WM phase, the spins within a supercell generate a cluster with a small total spin, but between the nearest-neighbor supercells are distributed randomly. Especially for the dimerized limit case, the spins within a supercell tend to point to opposite directions of the transverse field. In addition, we also investigate the influence of the three-site interaction, and find that the WM phase is absent as the strength of the three-site interaction increases. Our findings shed light on the complex behavior of the alternating XY chain and provide valuable insights for future studies.

Role of sea quarks in the nucleon transverse spin

Role of sea quarks in the nucleon transverse spin

The local electronic interaction and strain effects on transverse dynamical spin susceptibility of [formula omitted]-graphyne

We present the behaviors of dynamical transverse spin susceptibilities of undoped β-graphyne monolayer using the Green’s function approach in the context of Hubbard model Hamiltonian. Such dynamical spin susceptibility is proportional to inelastic cross section of neutron beam from the layer. Specially, the effects of magnetic field, on-site coulomb repulsion strength and strain parameter on the spin excitation modes of β-graphyne monolayer are investigated via calculating correlation function of transverse components of spin density operators. Our results show the increase of absolute value of compressive strain parameter leads to move the magnetic excitation modes to higher energies. Also the intensity of peaks in inelastic cross section reduces with absolute value of compressive strain parameter. We also show that applying biaxial tensile strain causes to decrease the intensity of peaks in dynamical transverse spin susceptibility. Finally the effects of magnetic field and on-site coulomb repulsion interaction strength on frequency dependence of dynamical spin structure factor of β-graphyne layer are studied. Moreover the frequency positions of spin excitation mode of β-graphyne monolayer have been investigated due to the effects of biaxial strains, applied magnetic field and Hubbard parameter strength in details.

Magnetoinduced spin Nernst effect in topological nodal-line semimetals

The spin Nernst effect (SNE) of a topological nodal-line semimetals (TNLSMs) nanowire in a four-terminal cross-bar device is studied. Based on the nonequilibrium Green’s function method combining with the tight-binding Hamiltonian, the spin Nernst coefficients Ns3z, Ns3x and Ns3y of the two thermal transport models (kz-y case and kx-y case) under a perpendicular magnetic field are obtained. The traditional SNE describes the transverse voltage and spin current caused by the longitudinal thermal gradient. The transverse spin current is generated by the spin–orbit interaction rather than the perpendicular magnetic field. Here we find that the spin Nernst coefficients are equal to zero at the zero-magnetic field, but have finite values for non-zero magnetic fields in TNLSMs. The spin Nernst coefficient is closely related to the strength of the magnetic field and temperature. With the increase of the magnetic field strength, the peak height of the spin Nernst coefficient increases. These results indicate that the SNE is induced by the perpendicular magnetic field in the present TNLSMs system, which can be considered as an anomalous spin Nernst phenomenon. In addition, we find that Ns3z displays a series of peaks when the transmission coefficient TLR jumps from one integer plateau to another, and the spin Nernst coefficient Ns3i (i=x,y,z) is an odd function of the Fermi energy EF with Ns3z/x/y(−EF)=−Ns3z/x/y(EF) in connection mode kz-y. For the kx-y connection mode, due to the presence of the mass term m opening the energy gap, a sudden jump of the transmission coefficient TLR in the vicinity of the energy gap edge causes a very larger peak for the spin Nernst coefficient Ns3z/x/y, and the symmetrical properties of the spin Nernst coefficient Ns3z/x/y are completely broken in the strong magnetic field. These results indicate that the spin Nernst coefficient in TNLSMs strongly depends on the thermal gradient direction and the transverse lead connection direction. The spin Nernst coefficient in TNLSMs has strongly spatial anisotropy, which can be used as the characterization of the experimental detection of TNLSMs.

Transverse spin and energy flow in Kerker scattering

Transverse spin and energy flow in Kerker scattering

Complete replica solution for the transverse field Sherrington-Kirkpatrick spin glass model with continuous-time quantum Monte Carlo method

Complete replica solution for the transverse field Sherrington-Kirkpatrick spin glass model with continuous-time quantum Monte Carlo method

Dynamics of quantum coherence and correlations in a transverse Ising spin chain environment

In this paper, we study the dynamical processes of quantum coherence and correlations for two central qubits system coupled with a transverse Ising spin chain. Suppose the initial state of quantum system is the Werner state and the initial state of environment is the ground state of spin chain, and the corresponding time evolution operator, decoherence factor and reduced density matrix are given. We deduce the analytical expressions of evolution of quantum coherence, entanglement and quantum discord. We find that when the spin chain undergoes quantum phase transition (QPT), the entanglement vanished at time [Formula: see text], and the coherence and discord vanished when the decoherence factor decayed to zero. Besides, we also find that the environmental scale N, coupling strength g and parameter P of Werner state do not change the evolution rules of quantum correlation, but accelerate their decay rate with these parameters’ increase.

Beam spin asymmetry measurements of deeply virtual π0 production with CLAS12

The new experimental measurements of beam spin asymmetry were performed for the deeply virtual exclusive π0 production in a wide kinematic region with the photon virtualities Q2 up to 6.6 GeV2 and the Bjorken scaling variable xB in the valence regime. The data were collected by the CEBAF Large Acceptance Spectrometer (CLAS12) at Jefferson Lab with longitudinally polarized 10.6 GeV electrons scattered on an unpolarized liquid-hydrogen target. Sizable asymmetry values indicate a substantial contribution from transverse virtual photon amplitudes to the polarized structure functions. The interpretation of these measurements in terms of the Generalized Parton Distributions (GPDs) demonstrates their sensitivity to the chiral-odd GPD E¯T, which contains information on quark transverse spin densities in unpolarized and polarized nucleons and provides access to the nucleon's transverse anomalous magnetic moment. Additionally, the data were compared to a theoretical model based on a Regge formalism that was extended to the high photon virtualities.

Polarization characteristics and transverse spin of Mie scattering.

Complicated polarization states in the near field of Mie scattering have aroused wide interest due to their broad potential applications. In this work, we investigated polarization properties, including polarization dimension, degree of nonregularity, and transverse electric-field spin, of scattering of a partially polarized plane wave by a dielectric nanosphere based on the rigorous Mie scattering theory. It is shown that with the decrease of the correlation coefficient, the polarization dimension and degree of nonregularity generally increase. In the limit of unpolarized incident light, a nearly-perfect nonregular polarization state (PN = 0.928) appears in the near field and the spin is transverse to the radial direction everywhere. The rich structure contained by the partially polarized scattered light offers an approach to manipulating the interaction between light and nanoparticles, which may lead to novel designs of nanoantenna, optical trap and sensing.

Revisiting physical mechanism of longitudinal photonic spin splitting and Goos-Hänchen shift

The intrinsic connection between the transverse photonic spin Hall effect (PSHE) and the Imbert–Fedorov shift has been well characterized. However, physical insights into the longitudinal photonic spin splitting associated with the Goos-Hänchen (GH) shift remain elusive. This paper aims to expand the theory of the PSHE generation mechanism from the transverse to the longitudinal case by examining the reflection of each spin component from an arbitrarily linearly polarized incident Gaussian beam on the air-dielectric interface. Unlike the transverse case, both spin-maintained and spin-flipped modes exhibit non-zero longitudinal displacements, with the latter being affected by the second-order expansion term of the Fresnel reflection coefficient with respect to the in-plane wave-vector component. Meanwhile, the polarization angle plays a crucial role in determining the longitudinal PSHE since each reflected total spin component is a coherent superposition of these two corresponding modes. Remarkably, the imaginary part of the relative permittivity of the dielectric significantly affects the symmetry of the longitudinal PSHE. Furthermore, the GH shift results from a superposition of individual spin states’ longitudinal displacements, taking into account their energy weights. By incorporating the corresponding extrinsic orbital angular momentum, we explore the generation mechanism of the symmetric/asymmetric longitudinal PSHE. The unified physical framework elucidating the longitudinal photonic spin splitting and GH shift provides a comprehensive understanding of the fundamental origin of the PSHE and beam shifts, paving the way for potential applications in spin-controlled nanophotonics.

Thermally generated spin current in the topological insulator Bi 2 Se 3

We present measurements of thermally generated transverse spin currents in the topological insulator Bi 2 Se 3 , thereby completing measurements of interconversions among the full triad of thermal gradients, charge currents, and spin currents. We accomplish this by comparing the spin Nernst magneto-thermopower to the spin Hall magnetoresistance for bilayers of Bi 2 Se 3 /CoFeB. We find that Bi 2 Se 3 does generate substantial thermally driven spin currents. A lower bound for the ratio of spin current density to thermal gradient is J s ∇ x T = (4.9 ± 0.9) × 10 6 ( ℏ 2 e ) A   m − 2 K   μ m − 1 , and a lower bound for the magnitude of the spin Nernst ratio is −0.61 ± 0.11. The spin Nernst ratio for Bi 2 Se 3 is the largest among all materials measured to date, two to three times larger compared to previous measurements for the heavy metals Pt and W. Strong thermally generated spin currents in Bi 2 Se 3 can be understood via Mott relations to be due to an overall large spin Hall conductivity and its dependence on electron energy.

Pure transverse spin perpendicular to wave propagation in multiple plane waves

Pure transverse spin perpendicular to wave propagation in multiple plane waves

Single Transverse Spin Asymmetry as a New Probe of Standard-Model-Effective-Field-Theory Dipole Operators.

Electroweak dipole operators in the standard-model-effective-field theory (SMEFT) are important indirect probes of quantum effects of new physics beyond the standard model (SM), yet they remain poorly constrained by current experimental analyses for lack of interference with the SM amplitudes in constructing cross section observables. In this Letter, we point out that dipole operators flip fermion helicities and so are ideally studied through single transverse spin asymmetries. We illustrate this at a future electron-positron collider with transversely polarized beams, where such an effect exhibits as azimuthal cosϕ and sinϕ distributions which originate from the interference of the electron dipole operators with the SM and are linearly dependent on their Wilson coefficients. This new method can improve the current constraints on the electron dipole couplings by 1-2 orders of magnitude, without depending on other new physics operators, and can also simultaneously constrain both their real and imaginary parts, offering a new opportunity for probing potential CP-violating effects.

Vectorial characterization of surface wave via one-dimensional photonic-atomic structure

Quantitative assessment of polarization properties of waves opens up the way for effective exploitation of them in many amazing applications. Tamm surface waves (TSW) that propagate on the interface of periodic dielectric media are proposed for many applications in numerous reports. The polarization state of TSW is not simply intuitive and would not be extracted from reflection spectra. Here considering orientation sensitive nature of the interaction between polarized electromagnetic wave and atom, we try to quantitatively characterize the polarization state of TSWs, excited on the surface of the 1D photonic crystal. To do this we performed direct contact between TSW and rubidium atomic gas by fabrication of a one-dimensional photonic crystal-atomic vapor cell and applied a moderate external magnetic field to create geometrical meaning and a sense of directionality to dark lines in reflection intensity. Our experimental results indicate that transition lines in the reflection spectrum of our hybrid system modify dependent on the orientation of the applied magnetic field and the transverse spin of TSW. We have used these changes to redefine the geometry of Voigt and Faraday for evanescent waves, especially Tamm surface waves. In the end, we performed simple mathematical operations on absorption spectra and extract the ratio of longitudinal and transverse electric field components of the polarization vector of TSW equal to 25\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\frac{2}{5}$$\\end{document}.

Comprehensive analysis of the influence of magnetic field gradients on single-beam SERF atomic magnetometer

Magnetic field gradients interfere with the coherence of the atomic ensemble and degrade the performance of the spin-exchange relaxation-free (SERF) atomic magnetometer. In this paper, the influence of magnetic field gradients is incorporated into the response model of single-beam atomic magnetometer, and the theoretical models of transverse relaxation rate, spin polarization and scale factor are established. Based on this model, we find that magnetic field gradients in different directions can cause varying degrees of degradation in the performance parameters of the magnetometer. The magnetic linewidths under different light power and magnetic field gradients are measured using the designed dedicated magnetic field gradients coils, and the spin polarization and magnetic field gradients relaxation rate are obtained through fitting. An unevenness and deviation of the curve are also observed in the experiments, indicating the presence of the magnetic field gradient of approximately 2 nT/cm in the magnetic shields. Furthermore, in a magnetic field gradient environment of 20 nT/cm, the mean of the long-term sensitivity decreased by 3.5 times and the standard deviation increased by 11 times. It shows that the magnetic field gradients will not only affect the signal-to-noise ratio, but also make the magnetometer more vulnerable to external interference when working. The sensitivity and stability of magnetometer will be greatly reduced. The research in this article provides a theoretical and experimental basis for eliminating the influence of magnetic field gradients and improving the accuracy of magnetic field measurements.