Measurement Of Spin Polarization Research Articles

Spin Polarization Measurement in SERF Comagnetometer Based on Phase‐Frequency Response of Magnetic Field

Spin Polarization Measurement in SERF Comagnetometer Based on Phase‐Frequency Response of Magnetic Field

Determination of the polarization of Xe nuclear spin using transverse and longitudinal Rb in-situ magnetometers in NMR co-magnetometers

NMR co-magnetometers, as novel atomic sensors, can measure the angular velocity information in inertial measurements by detecting the spin precession of Xe nuclei. The Xe polarization plays a crucial role in the sensing unit of co-magnetometers, as it enhances the signal-to-noise ratio (SNR) and sensitivity of NMR sensors. Here we elucidated the Rabi dynamics of Xe nuclear spin and demonstrated two methods to determine the Xe polarization based on the classical Bloch equations. By detecting the optical rotation angle signal, we acquired the amplitude and the phase variations information in two methods, respectively. The transverse magnetometer relies on the amplitude of the free induction decay (FID) signal and applies a short pulse to flip the Xe fields into the transverse plane, enabling precise measurements. On the other hand, the longitudinal magnetometer offers an intuitive approach to measuring the demodulated phase variations by capturing the repetitive flips of longitudinal Xe fields. This paper discusses the advantages and disadvantages of both proposed methods, with the aim of enhancing the accuracy and authenticity of nuclear spin polarization measurements for noble gas atoms in atomic sensors.

Geometric Amplitude Accompanying Local Responses: Spinor Phase Information from the Amplitudes of Spin-Polarized STM Measurements.

Solving the Hamiltonian of a system yields the energy dispersion and eigenstates. The geometric phase of the eigenstates generates many novel effects and potential applications. However, the geometric properties of the energy dispersion go unheeded. Here, we provide geometric insight into energy dispersion and introduce a geometric amplitude, namely, the geometric density of states (GDOS) determined by the Riemann curvature of the constant-energy contour. The geometric amplitude should accompany various local responses, which are generally formulated by the real-space Green's function. Under the stationary phase approximation, the GDOS simplifies the Green's function into its ultimate form. In particular, the amplitude factor embodies the spinor phase information of the eigenstates, favoring the extraction of the spin texture for topological surface states under an in-plane magnetic field through spin-polarized STM measurements. This work opens a new avenue for exploring the geometric properties of electronic structures and excavates the unexplored potential of spin-polarized STM measurements to probe the spinor phase information of eigenstates from their amplitudes.

Spin polarization in relativistic heavy-ion collisions

Polarization has opened a new physics chapter in relativistic heavy-ion collisions. Since the first prediction and experimental observation of global spin polarization, a lot of progress has been made in understanding its features, both at experimental and theoretical levels. In this paper, we give an overview on the recent advances in this field. The covered topics include a review of measurements of global and local spin polarization of hyperons and the global spin alignment of vector meson’s. We account for the basic theoretical framework to describe spin polarization in a relativistic fluid such as the Quark–Gluon Plasma, including statistical quantum field theory and local thermodynamic equilibrium, spin hydrodynamics, relativistic kinetic theory with spin and coalescence models.

Systematic characterization of a Ne, Ar, Kr rare-gas moderated positron beam and spin polarization measurements

In this work we report on the systematic characterization of a rare-gas moderated magnetically-transported continuous positron beam based on a 22Na radioactive source. The characterization was performed with three different rare-gas solid moderators: Ne, Ar, and Kr. Each moderator was deposited and then thermal annealed at temperature ∼ 35 % and ∼ 30 % lower than the melting point, respectively. Tests of moderation/magnetic transport efficiency of the apparatus have shown a maximum efficiency of 1.8 10-3, 2.0 10-3 and 0.6 10-3 for Ne, Ar, and Kr, respectively. The average longitudinal kinetic energy of positrons was found to be ∼ 0.95 eV, ∼1.25 eV, and ∼ 0.45 eV for Ne, Ar, and Kr moderator, respectively.The spin polarization measurement of moderated positrons was performed by using the Doppler broadening of the annihilation γ-rays from positronium formed in oxidized nanochanneled silicon positron/positronium converters. Polarization values of 0.30 ± 0.01, 0.29 ± 0.01 and 0.29 ± 0.01 were found for Ne, Ar, and Kr moderator, respectively.

In Situ Spin Polarization Measurement Method and Identification of Optimal Spin Polarization Range in Atomic Magnetometer

AbstractIn this study, an in situ measurement method of spin polarization in single‐beam atomic magnetometer is presented. Modeling magnetic linewidth by incorporating nonlinear attenuation along the propagation direction of light and employing the output response equation of magnetometers at zero‐field resonance. Utilizing the model for fitting to extract relaxation rate information, the photon absorption cross‐sections at three temperatures are estimated to be , , and , respectively. Further, the spin polarization curves are obtained by introducing the spin polarization equations. Given the diminishing marginal utility resulting from the enhancement of performance through increased spin polarization, long‐term sensitivity is employed to determine optimal spin polarization range. The optimal long‐term sensitivity for four displayed states is (@31.5Hz), while the ultimate minimum sensitivity is 10.7 (@31.5Hz). The optimal spin polarization ranges at three temperatures are 78.9%–87.1%, 82.3%–88.5%, and 84.5%–88.4%, respectively. The measurement method applied to single‐beam magnetometer can be easily extended to multi‐axis vector magnetometer. The determination of optimal spin polarization range is of great significance for the performance and stability of the magnetometer system, improving the sensitivity of magnetic field measurement, and ensuring its widespread application in bio‐magnetic measurement.

Recent advances in application-oriented new generation diluted magnetic semiconductors

Diluted ferromagnetic semiconductors (DMSs) have attracted widespread attention in last decades, owing to their potential applications in spintronic devices. But classical group-III, IV, and V elements based DMS materials, such as (Ga, Mn)As which depend on heterovalent (Ga<sup>3+</sup>, Mn<sup>2+</sup>) doping, cannot separately control carrier and spin doping, and have seriously limited chemical solubilities, which are disadvantages for further improving the Curie temperatures. To overcome these difficulties, a new-generation DMS with independent spin and charge doping have been designed and synthesized. Their representatives are I-II-V based Li(Zn, Mn)As and II-II-V based (Ba, K)(Zn, Mn)<sub>2</sub>As<sub>2</sub>. In these new materials, doping isovalent Zn<sup>2+</sup> and Mn<sup>2+</sup> introduces only spins, while doping heterovalent non-magnetic elements introduces only charge. As a result, (Ba, K)(Zn, Mn)<sub>2</sub>As<sub>2</sub> achieves Curie temperature of 230 K, a new record among DMS where ferromagnetic orderings are mediated by itinerate carriers. Herein, we summarize the recent advances in the new-generation DMS materials. The discovery and synthesis of several typical new-generation DMS materials are introduced. Physical properties are studied by using muon spin relaxation, angle-resolved photoemission spectroscopy and pair distribution function. The physical and chemical pressure effects on the title materials are demonstrated. The Andreev reflection junction based on single crystal and the measurement of spin polarization are exhibited. In the end, we demonstrate the potential multiple-parameter heterojunctions with DMS superconductors and antiferromagnetic materials.

Correlation effects on topological end-states in finite-size graphene nanoribbons in the GW approximation

Finite size armchair graphene nanoribbons (GNRs) of different families are theoretically studied using the Hubbard model in both mean-field and GW approximations, including spin correlation effects. It is shown that correlation primarily affect the properties of topological end states of the nanoribbons. A representative structure of each of the three GNR families is considered but the seven-atom width nanoribbon is studied in detail and compared to previously published experimental results, showing a clear improvement when correlations are included. Using isolated spin contributions to scanning tunneling microscopy (STM) simulations, spin-polarized measurements in STM are also suggested to help distinguish and highlight correlation effects.

Ultrafast Hidden Spin Polarization Dynamics of Bright and Dark Excitons in 2H-WSe_{2}.

We performed spin-, time- and angle-resolved extreme ultraviolet photoemission spectroscopy of excitons prepared by photoexcitation of inversion-symmetric 2H-WSe_{2} with circularly polarized light. The very short probing depth of XUV photoemission permits selective measurement of photoelectrons originating from the top-most WSe_{2} layer, allowing for direct measurement of hidden spin polarization of bright and momentum-forbidden dark excitons. Our results reveal efficient chiroptical control of bright excitons' hidden spin polarization. Following optical photoexcitation, intervalley scattering between nonequivalent K-K^{'} valleys leads to a decay of bright excitons' hidden spin polarization. Conversely, the ultrafast formation of momentum-forbidden dark excitons acts as a local spin polarization reservoir, which could be used for spin injection in van der Waals heterostructures involving multilayer transition metal dichalcogenides.

Spin‐Decoupling and In‐Situ Nuclear Magnetometer with Hyperpolarized Nuclear Spin

AbstractThis paper investigates the dynamical properties of the spin‐coupling ensemble, with a focus on the spin‐decoupling phenomenon. The nuclear spin in such systems is significantly impacted by the electron spin when the main magnetic field approaches the Fermi contact field of nuclear spin, leading to measurement inaccuracies. A comprehensive dynamics model of the electron‐nuclear spin coupling ensemble has been established and analyzed. It proposes that the primary magnetic field augmenting effectively disentangles the precession frequency of the two spin‐coupling species, thereby yielding a spin‐decoupled state. Such a state allows nuclear spin serves as a high sensitive element for magnetic field measurements, while electron spin serves as a probe to acquire the precession of nuclear spin. With proposed method, a magnetic field resolution of 0.75 nT in a 12000 nT environment is achieved, indicating potential for magnetic field detection in geomagnetic environments. It further demonstrates measurements of electron spin Fermi contact interaction and polarization based on spin‐decoupling and in situ nuclear spin precession, results indicate measurement errors close to 1%. These results demonstrate the effectiveness of our approach in improving the accuracy and sensitivity of magnetic field measurements in spin‐coupled systems such as co‐magnetometers, nuclear magnetic resonance gyroscopes, and nuclear magnetometers.

Measurement of optically-pumped electron spin polarization in n-GaAs at high external electric fields

We use the technique of time-resolved Kerr rotation (TRKR) to measure the electron spin polarization generated by optical spin pumping in an n-type gallium arsenide (GaAs) epilayer when an external electric field is simultaneously applied on the sample. The drift of the electron spins under the influence of the external electric field is captured with spatial scans of the pump–probe separation. A significant decay in the magnitude of electron spin polarization with electric field is observed and is attributed to the increased inhomogeneous broadening caused by the field-induced drift and the hot electron effects. We extend the electric field range to as high as the Gunn threshold field in the measurement and we do not observe a spin amplification effect due to the spin Gunn effect under our experimental scheme.

Spin-polarisation measurement using NbN-insulator-ferromagnet tunnel junction with oxidized barrier

We report a two-step process for the fabrication of superconductor-insulator-normal metal tunnel junctions using NbN as the superconducting electrode and its surface oxide as the insulating tunnel barrier, and investigate its efficacy in measuring spin-polarisation of ferromagnets using the Meservey-Tedrow technique. We observe that for NbN film thickness below 10 nm, under the application of parallel magnetic field, the superconducting density of states show clear “Zeeman” splitting into spin-up and spin-down sub-bands. Tunnelling measurements on devices where ferromagnetic Co is used as the normal electrode shows that these devices can be used to measure spin polarisation of a ferromagnet at temperatures up to 1.6 K. The simplicity of our fabrication process makes NbN a very attractive candidate for spin polarisation measurements. Some limitations of this process are also discussed.

In-situ measurement of the electron spin polarization by controlling its distribution in atomic ensembles.

The determination of electron spin polarization by controlling the atomic population distributions of ground states has been proposed. The polarization could be deduced by generating different population symmetries by polarized lights. The polarization of the atomic ensembles was decoded from optical depth in different transmissions of linearly and elliptic polarized lights. The feasibility of the method has been validated theoretically and experimentally. Moreover, the influences of relaxation and magnetic fields are analyzed. The transparency induced by high pump rates are investigated experimentally, and the influences of ellipticity of lights are also discussed. The in-situ polarization measurement was achieved without changing optical path of atomic magnetometer, which provides a new way to interrogate the performance of atomic magnetometer and in-situ monitoring the hyperpolarization of nuclear spins for atomic co-magnetometer.

Nonzero-Order Resonances in Single-Beam Spin-Exchange Relaxation-Free Magnetometers

Zero-field optically pumped magnetometers operating in the spin-exchange relaxation-free (SERF) regime have been extensively studied, and usually depend on zeroth-order parametric resonance to measure the magnetic field. However, the studies conducted on this topic lack thorough analyses and in-depth discussion of nonzero-order magnetic resonances in single-beam SERF magnetometers. In this paper, we analyzed the nonzero-order resonance, especially the first-order resonance, based on a single-beam SERF magnetometer, and discussed its various applications. A comprehensive theoretical analysis and experiments were conducted with respect to multiple functions, including nonzero finite magnetic field measurements, spin polarization measurement, and in situ coil constant calibration. The results showed that first-order resonance can be utilized for nonzerofinite magnetic field measurements, and the spin polarization of alkali-metal atoms can be determined by measuring the slowing-down factor using the resonance condition. Furthermore, acquiring the first-order resonance point at an equivalent zero pump light power through fitting offers an approach for quick and precise in situ coil constant calibration. This study contributes to the applications of SERF magnetometers in nonzero finite magnetic fields.

Relativistic hydrodynamics with spin in the presence of electromagnetic fields

We extend the classical phase-space distribution function to include the spin and electromagnetic fields coupling and derive the modified constitutive relations for charge current, energy-momentum tensor, and spin tensor. Because of the coupling, the new tensors receive corrections to their perfect fluid counterparts and make the background and spin fluid equations of motion communicate with each other. We investigate special cases which are relevant in high-energy heavy-ion collisions, including baryon free matter and large mass limit. Using Bjorken symmetries, we find that spin polarization increases with increasing magnetic field for an initially positive baryon chemical potential. The corrections derived in this framework may help to explain the splitting observed in Lambda hyperons spin polarization measurements.

Conceptual design of DIII-D experiments to diagnose the lifetime of spin polarized fuel

In magnetic fusion experiments, the cross sections for the D-T and D-3He fusion reactions are increased by as much as 50% if the fuel remains spin polarized parallel to the magnetic field. The goal of this study is to assess the feasibility of lifetime measurements of spin polarization, in magnetic fusion relevant conditions, on the DIII-D tokamak using relative changes in charged fusion product (CFP) loss measurements that depend upon the differential fusion cross section dσ/dΩ. Relative measurements that capture changes in the escaping CFP pitch, poloidal, and energy distributions are studied in two realistic TRANSP calculated plasma scenarios: (a) vector-polarized 3He and D pellets are injected into a hot hydrogen plasma to produce thermonuclear reactions, and (b) a tensor-polarized deuterium pellet is injected into an L-mode hydrogen background plasma that includes unpolarized 3He neutral beam injection. Ideal CFP signals in both scenarios show substantial pitch sensitivity to polarization for 14.7 MeV proton detection at a poloidal angle of (on the outer wall in the ion direction), and strong sensitivity to polarization for 3.6 MeV alpha flux detection by an array of poloidal detectors. Energy-resolved measurements of 14.7 MeV protons are also sensitive to the degree of polarization for the port in the beam-plasma scenario. A realistic assessment of CFP signals in the thermonuclear scenario show count rates in the range of cps for pitch-resolved proton detection and cps for alpha flux measurements. Reduced chi-squared calculations show polarization lifetime measurements are feasible for either proton or alpha detection of both enhanced or suppressed polarization for the thermonuclear scenario. Measurements of gamma rays produced in the weak branch complement the CFP measurements.

Spin polarization and spin-dependent scattering of holes observed in transverse magnetic focusing

In two-dimensional hole systems, the Rashba spin-orbit interaction leads to a spin dependent momentum. A perpendicular magnetic field spatially separates holes with different spins, creating a mass spectrometer for spin. Spin-resolved magnetic focussing has been used to measure spin polarization from the amplitude of magnetic focussing peaks. In this work, the authors show that the ${k}^{3}$ form of the Rashba spin-orbit interaction term for semiconductor holes changes the scattering rate, which has an exponential effect on the focussing peak amplitude. This result further demonstrates the impact of the Rashba spin-orbit interaction in the field of semiconductor hole spin physics.

Spin polarization and alignment in heavy-ion collisions

We report the measurements of global spin polarization of hyperons (PΛ) from FAIR, RHIC and LHC energies. The PΛ continues to follow an increasing trend at √SNN < 7.7 GeV indicating that enormous vorticity prevails even in hadronic dominant region. New measurements of local spin polarization (Pz,2) from isobar collisions follow the same pattern observed in previous RHIC and LHC energies. An observable motivated by predicted baryonic Spin Hall Effect, the net local polarization (Pz,2net), show a negative value in Au+Au collisions at √SNN = 19.6 and 27 GeV. The first Pz measurement with respect to third order harmonic in 200 GeV RHIC isobar collisions shows a non-zero sine modulation, indicating the presence of complex vortical structure in the medium. Surprising new patterns of spin alignment (ρ00) for various vector mesons (K*0, K*±, ϕ and J/ψ emerged at both RHIC and LHC energies. The large deviation in ρ00 of several species poses challenge to the theory.

Spin Polarization Measurements in Relativistic Heavy-ion Collisions

Spin Polarization Measurements in Relativistic Heavy-ion Collisions

Polarization in heavy ion collisions: A theoretical review

In these proceedings I discuss the recent progress in the theory of spin polarization in relativistic fluids. To date, a number of studies have begun to examine the impact of the shear tensor on the local spin polarization and whether this contribution can restore agreement between the measurements and the predictions obtained from a polarization induced by the gradients of the plasma. I present the derivation of the spin polarization vector of a fermion at local thermal equilibrium and I discuss the role of pseudo-gauge transformations and of dissipative effects. I list what we can learn from the polarization measured at lower energies. Finally, I discuss possible applications of spin polarization measurements in relativistic heavy ion collisions.