Spin Motion Research Articles

Spin transport at a Pt/InAs quantum well interface using spin Hall and Rashba effects

In the field of spintronics, charge-to-spin conversion without a ferromagnetic material has attracted intense interest from researchers seeking to realize a fully electrical spin device because this design obviates the need for magnetic field control of magnetization. Instead of spin injection from a ferromagnetic source, spin-Hall-induced pure spin current has recently attracted considerable interest for transferring spin information into the semiconductor channel. In the present work, the spin is injected from a platinum electrode via the direct spin Hall effect and is subsequently detected in a strong Rashba channel via the inverse spin Hall effect. Before being detected, the spin state is modulated by a gate voltage; the signal observed with various channel lengths and gate voltages demonstrates this Rashba precessional modulation. The addition of Zeeman precession induced by an external magnetic field provides the signal-elucidating definite spin motion in the channel and clear interplay between the Rashba and Zeeman processions. Our approach opens a fascinating possibility for realizing a ferromagnet-free system for use in low-power and high-temperature spin transistors.

Features of the Coupled Nuclear–Electron Spin Precession in the Bose–Einstein Condensate of Magnons

The experimental detection of the Bose-Einstein condensate of magnons in coupled nuclear-electron spin precession in antiferromagnets brings the prospect of its use for magnonics and computer calculations. In particular, an attractive feature of such systems is a relatively large spin coherence time compared to traditional iron yttrium garnet samples. However, the observed Bose-Einstein condensation of magnons contradicts the Suhl-Nakamura model and the Bloch equations, which are usually used for these systems. The results of a direct experiment in antiferromagnetic MnCO3 performed in this work indicate that the Suhl-Nakamura model and the Bloch equations cannot adequately describe the coupled nuclear-electron spin motion at large levels of magnon excitation.

A Fast Bistatic ISAR Imaging Approach for Rapidly Spinning Targets via Exploiting SAR Technique

Because of the large range of cell migration (RCM) and nonstationary Doppler frequency modulation (DFM) produced by non-cooperative targets with rapid spinning motions, it is difficult to efficiently generate a well-focused bistatic inverse synthetic aperture radar (ISAR) by use of the conventional imaging algorithms. Utilizing the property of the inherent azimuth spatial invariance in strip-map synthetic aperture radar (SAR) imaging mode, in this work, an efficient bistatic ISAR imaging approach based on circular shift operation in the range-Doppler (RD) domain is proposed. First, echoes of rapidly spinning targets are transformed into the RD domain, whose exact analytical is derived on the basis of the principle of stationary phase (POSP). Second, the RCM is corrected by using an efficient circular shift operation in the RD domain. By doing so, the energies of a scatterer that span multiple range cells are concentrated into the same range cell, and the time-varying DFM can also be compensated along the rotating radius direction. Compared with existing methods, the proposed method has advantages in its computational complexity, avoiding the interpolation and multi-dimensional search operation, and in its satisfactory imaging performance under low signal to noise ratio (SNR) conditions thanks to the two-dimensional coherent integration gain utilized. Finally, several numerical simulations are conducted to show the validity of the proposed algorithm.

Elementary Laser‐Less Quantum Logic Operations with (Anti‐)Protons in Penning Traps

AbstractStatic magnetic field gradients superimposed on the electromagnetic trapping potential of a Penning trap can be used to implement laser‐less spin–motion couplings that allow the realization of elementary quantum logic operations in the radio‐frequency regime. An important scenario of practical interest is the application to g‐factor measurements with single (anti‐)protons to test the fundamental charge, parity, time reversal (CPT) invariance as pursued in the Baryon Antibaryon Symmetry Experiment (BASE) collaboration. The classical and quantum behavior of a charged particle in a Penning trap with a superimposed magnetic field gradient is discussed. Using analytic and numerical calculations, it is found that it is possible to carry out a SWAP gate between the spin and the motional qubit of a single (anti‐)proton with high fidelity, provided the particle has been initialized in the motional ground state. The implications of the findings for the realization of quantum logic spectroscopy in this system are discussed.

Derivation of the Reynolds equation in cylindrical coordinates applicable to the slipper/swash plate interface in axial piston pumps

Although many tribology references have presented the Reynolds equation in cylindrical coordinates, they may not be applicable to the slipper/swash plate interface in axial piston pumps due to complex macro and micro motions of slippers. Therefore, this paper derives the generalized Reynolds equation in cylindrical coordinates for this interface from momentum and continuity equations. Also, the boundary velocity conditions for the Reynolds equation are evaluated based on the kinematics of slippers, which accounts for the spinning motion. Compared with the traditional Reynolds equation for the slipper/swash plate interface, the new Reynolds equation in this work considers the geometric squeeze and centrifugal terms and has a different form of Couette terms.

Nonlinear vibration of a deploying laminated Rayleigh beam with a spinning motion in hygrothermal environment

The free vibration of a deploying laminated beam with spinning motion in hygrothermal environment is studied. The model of this system is given within the framework of the Rayleigh beam theory and the von Karman nonlinear strain theory. The nonlinear dynamic equilibrium equation of the cantilever boundary condition is established based on Hamilton's principle with considering the combined effects of the axial motion, transverse vibration, spinning motion, and hygrothermal environment. The frequencies of the system are numerically determined by using the Newmark method. The detailed parameter analyses are provided to investigate the effects of the deploying speed, the spinning speed, the temperature variation, the moisture concentration, and the fiber direction angle on frequency and the corresponding sensitivity.

Magnus effect for roll-decoupled canards on a spinning body of revolution

PurposeSpinning slender bodies are affected by lateral Magnus forces and moments when exposed to cross-flow. The effects occurring for spinning bodies of revolution in combination with stabilising or control surfaces such as canards are not yet fully explained. Therefore the present work aims to investigate the phenomena arising from the interactions of a roll-decoupled guidance unit with a spinning rear body are investigated.Design/methodology/approachA generic tangential-ogive-cylinder projectile equipped with deflectable canards on a roll-decoupled nose is investigated by means of 3D Reynolds-averaged Navier–Stokes simulations at Mach number 2 for angles of attack up to 22 degrees. Different canard deflection angles up to 9 degrees are considered. Global aerodynamic coefficients as well as local flow fields are analysed to explain the interactions occurring between the roll-decoupled guidance unit and the spinning rear body.FindingsThe deflected canards lead to flow interactions resulting in lateral forces and moments even without a spinning motion of the rear part. Depending on the canard deflection angles, these forces act in or against the direction of the classical Magnus effect. For angles of attack smaller than 10 degrees it is possible for the current body geometry to directly superpose the lateral effects resulting from the fins for the non-spinning model with those occurring for the non-finned but spinning model to obtain the total forces and moments acting on a spinning model with canted canards. However, the lateral effects generated on the guidance unit itself are insignificant compared to the canard-induced effects on the rear body.Originality/valueA detailed analysis of the interaction effects arising from a decoupled guidance unit containing canards with a non-spinning/spinning rear body is performed and the underlying phenomena are revealed.

Ellipticity control of high-order harmonic generation with nearly orthogonal two-color laser fields

Elliptically polarized high-order harmonics opens a path toward the study of ultrafast dynamics in circular dichroism of magnetic materials, chiral molecules, and electronic spin motion. Recently, efficient high-order harmonic generation with controllable ellipticity has attracted considerable attention in experiment and theory. Here, we experimentally demonstrate a scenario using cross-linearly-polarized two-color fields consisting of a fundamental field and its second harmonic (SH). Through adjusting the relative phase, crossing angle, and intensity ratio of the cross-linearly-polarized two-color field, we obtain ellipticity-tunable high-order harmonics, with ellipticity up to $\ensuremath{\varepsilon}=0.73$. Meanwhile, the elliptically polarized high-order harmonics preserve high efficiency. Furthermore, when the intensity of the SH field is stronger than that of the fundamental field, the even order harmonics will become several times stronger than the odd order harmonics with opposite helicity.

The Effect of Brush Motion and Rinsing When Manually Cleaning Cannulated Medical Devices.

Cleaning cannulated medical devices can be challenging for perioperative and sterile processing department personnel. We performed a laboratory experimental study to evaluate differences in cleaning effectiveness using either a back-and-forth or helical spinning brushing motion and the effect of rinsing the bristles at each reintroduction of the brush in the lumen. We also tested the lumen cleanliness after high-pressure water cleansing without brushing. We inspected the devices to determine whether visible soil remained, and we measured the amount of residual organic matter using adenosine triphosphate testing to determine cleaning method effectiveness. The results showed that rinsing the brush during cleaning decreased the amount of organic material that remained in the lumen. A helical spinning motion with brush rinsing at each reintroduction of the brush may be more effective than back-and-forth brushing with rinsing, but additional testing with a larger sample size is required to determine whether this result is replicable.

Tidal oscillations of rotating hot Jupiters

ABSTRACT We calculate small amplitude gravitational and thermal tides of uniformly rotating hot Jupiters composed of a nearly isentropic convective core and a geometrically thin radiative envelope. We treat the fluid in the convective core as a viscous fluid and solve linearized Navier–Stokes equations to obtain tidal responses of the core, assuming that the Ekman number, Ek, is a constant parameter. In the radiative envelope, we take account of the effects of radiative dissipations on the responses. The properties of tidal responses depend on thermal time-scales τ* in the envelope and Ekman number, Ek, in the core and on whether the forcing frequency ω is in the inertial range or not, where the inertial range is defined by |ω| ≤ 2Ω for the rotation frequency Ω. If Ek ≳ 10−7, the viscous dissipation in the core is dominating the thermal contributions in the envelope for τ* ≳ 1 d. If Ek ≲ 10−7, however, the viscous dissipation is comparable to or smaller than the thermal contributions and the envelope plays an important role to determine the tidal torques. If the forcing is in the inertial range, frequency resonance of the tidal forcing with core inertial modes significantly affects the tidal torques, producing numerous resonance peaks of the torque. Depending on the sign of the torque in the peaks, we suggest that there exist cases in which the resonance with core inertial modes hampers the process of synchronization between the spin and orbital motion of the planets.

An Integrated Model to Characterize Comprehensive Stiffness of Angular Contact Ball Bearings

The bearing dynamic behaviors will be complicated due to the changes in the geometric sizes and relative positions of the bearing components at high speed. In this paper, based on the Hertz contact theory, elastohydrodynamic lubrication (EHL) model, and Jones’ bearing theory, the comprehensive stiffness model of the angular contact ball bearing is proposed in consideration of the effects of elastic deformation, centrifugal deformation, thermal deformation, and the ball spinning motion. The influences of these factors on bearing dynamic stiffness are investigated in detail. The calculation results show that the centrifugal deformation and thermal deformation increase with the increase in rotation speed. When the centrifugal deformation and thermal deformation are considered, the bearing radial contact stiffness increases as the speed increases, whereas the axial contact stiffness and the angular contact stiffness decrease. When the deformations and the EHL are all considered, the comprehensive bearing stiffness decreases with the increasing speed. It is also found that the spinning motion of the ball causes the comprehensive bearing stiffness to increase.

Inversion of the Axial Information during Oxidative Aromatization in the Synthesis of Axially Chiral Biaryls with Organocatalysis as a Key Step.

Invited for the cover of this issue is the group of Yujiro Hayashi at the University of Tohoku University. The image depicts the spinning motion of a figure skater, which illustrates the transformation of the chiral information investigated in this work. Read the full text of the article at 10.1002/chem.201905814.

Possible Detection of Magnetic Anomaly During Tsunami Events in Indonesian Regions Using Global Magnetogram Records

Ocean flow generates secondary, weak magnetic signals relative to the main field induced by the Earth spinning motion, where the secondary signals lead to magnetic anomaly. The anomaly were apparently observed as short-lived variation in secondary field components, namely the vertical bz and horizontal components bH , respectively, during tsunami occurrence. In this study, maximum amplitudes associated with these components were determined using theoretical approaches and field records on global magnetogram provided by INTERMAGNET and BCMT. The roles played by a depth ratio of h/L where h and L are the ocean depth and characteristic length, respectively, and a speed ratio of c/cs where c and cs are the speed for linear long wave solution and the complex speed involving ocean diffusion, respectively, are here examined using Indonesian case studies of tsunami with respect to trans-Pacific tsunamis as reference. For cases with advection dominance, it was found that frozen-flux theory can be used to estimate bz and bH, consistent with values provided by the global magnetic institutions. In short, whereas bz is a measure of water surface elevation and hence tsunami height offshore, bH is an indicator for tsunami propagation direction. Detection of magnetic anomaly prior to tsunami arrivals at coastal zones is thus possible, making it crucial for tsunami early warning.

Spinning gasodynamic projectile system identification experiment design

PurposeThe purpose of this paper is to present the methodology that was used to design a system identification experiment of a generic spinning gasodynamic projectile. For this object, because the high-speed spinning motion, it was not possible to excite the aircraft motion along body axes independently. Moreover, it was not possible to apply simultaneous multi-axes excitations because of the short time in which system identification experiments can be performed (multi-step inputs) or because it is not possible to excite the aircraft with a complex input (multi-sine signals) because of the impulse gasodynamic engines (lateral thrusters) usage.Design/methodology/approachA linear projectile model was used to obtain information about identifiability regions of stability and control derivatives. On this basis various sets of lateral thrusters’ launching sequences, imitating continuous multi-step inputs were used to excite the nonlinear projectile model. Subsequently, the nonlinear model for each excitation set was identified from frequency responses, and the results were assessed. For comparison, the same approach was used for the same projectile exited with aerodynamic controls.FindingsIt was found possible to design launching sequences of lateral thrusters that imitate continuous multi-step input and allow to obtain accurate system identification results in specified frequency range.Practical implicationsThe designed experiment can be used during polygonal shooting to obtain a true projectile aerodynamic model.Originality/valueThe paper proposes a novel approach to gasodynamic projectiles system identification and can be easily applied for similar cases.

Room-temperature terahertz anomalous Hall effect in Weyl antiferromagnet Mn3Sn thin films

Antiferromagnetic spin motion at terahertz (THz) frequencies attracts growing interests for fast spintronics, however, their smaller responses to external field inhibit device application. Recently the noncollinear antiferromagnet Mn3Sn, a Weyl semimetal candidate, was reported to show large anomalous Hall effect (AHE) at room temperature comparable to ferromagnets. Dynamical aspect of such large responses is an important issue to be clarified for future THz data processing. Here the THz anomalous Hall conductivity in Mn3Sn thin films is investigated by polarization-resolved spectroscopy. Large anomalous Hall conductivity {mathrm{Re}};sigma _{xy}left( omega right) sim 20;{mathrm{Omega }}^{ - 1}{mathrm{cm}}^{ - 1} at THz frequencies is clearly observed as polarization rotation. A peculiar temperature dependence corresponding to the breaking/recovery of symmetry in the spin texture is also discussed. Observation of the THz AHE at room temperature demonstrates the ultrafast readout for the antiferromagnetic spintronics using Mn3Sn, and will also open new avenue for studying nonequilibrium dynamics in Weyl antiferromagnets.

Statistical sensitivity estimates for oscillating electric dipole moment measurements in storage rings

In this paper analytical expressions are derived to describe the spin motion of a particle in magnetic and electric fields in the presence of an axion field causing an oscillating electric dipole moment (EDM). These equations are used to estimate statistical sensitivities for axion searches at storage rings. The estimates obtained from the analytic expressions are compared to numerical estimates from simulations in Chang et al. (Phys Rev D 99(8):083002, 2019). A good agreement is found.

The microscopic origin of spin-orbit mediated spin-flips

Laser induced ultrafast demagnetization is a powerful process by which the magnetic moment of a material can be modified on femtosecond timescales. However, to eventually utilize this process in technology, it is crucial that we develop a thorough understanding of the physical mechanisms involved. Based on ab initio simulations, spin-orbit mediated spin-flips have been proposed as one form of ultrafast demagnetization. In this paper, we explore this mechanism in more detail using time-dependent density functional theory (TDDFT) to study demagnetization in bulk Ni. We show why spin-orbit coupling (SOC) causes spin-flips by highlighting the importance of circulating spin currents induced by the coupling between the electronic spin and orbital motion. We present both a mathematical and heuristic picture of how SOC can cause demagnetization. Furthermore, we show that same arguments can be used to understand how the spin angular momentum is transferred to the lattice during laser induced demagnetization in a realistic material.

On the stability of certain motions of a rigid body-gyrostat in an incompressible ideal fluid

This work is devoted to investigating the stability of motion of a rigid body-gyrostat in an incompressible ideal fluid. This motion is assumed to happen under the action of neutral forces (buoyancy and gravity) whose centers are not coincide. The equations of motion are introduced, and they are expressed by means of the Hamiltonian function in the framework of the Lie-Poisson system. We prove that the problem of motion of a gyrostat in an incompressible ideal fluid is equivalent to the general problem of the motion of a rigid body under the action of a combination of potential and gyroscopic forces. We endeavor for studying the stability of two possible types of stationary solutions which describe the spin motion and non-spin motion of a gyrostat. For the non-spin motion, we consider two stationary solutions for which the translation motion is either in direction of the gravity or in the perpendicular direction on it. For the spin motion, we consider an stationary solution describing physically translation along and rotation about the same axis, say, the third one. The linear approximation method is applied to get the sufficient conditions for instability or in other words, the necessary conditions for stability. The energy-Casimir method is utilized to provide sufficient conditions for stability.

Deuteron Quadrupolar Chemical Exchange Saturation Transfer (Q-CEST) Solid-State NMR for Static Powder Samples: Approach and Applications to Amyloid-β Fibrils.

We provide an experimental and computational framework for 2 H quadrupolar chemical exchange saturation transfer NMR experiments (Q-CEST) under static solid-state conditions for the quantification of dynamics on μs-ms timescales. Simulations using simple 2-site exchange models provide insights into the relation between spin dynamics and motions. Biological applications focus on two sites of amyloid-β fibrils in the 3-fold symmetric polymorph. The first site, the methyl group of A2 of the disordered N-terminal domain, undergoes diffusive motions and conformational exchange due to transient interactions. Earlier 2 H rotating frame relaxation and quadrupolar CPMG measurements are combined with the Q-CEST approach to characterize the multiple conformational states of the domain. The second site, the methyl group of M35, spans the water-accessible cavity inside the fibrils' core and undergoes extensive rotameric exchange. Q-CEST permits us to refine the rotameric exchange model for this site and allows the more precise determination of populations and rotameric exchange rate constants than line shape analysis.

Dynamic Estimation of Spin Spacecraft Based on Multiple-Station ISAR Images

Dynamic estimation of spin spacecraft is a challenge and plays a significant role in space situation awareness applications like potential space collision warning. Based on remote sensing technologies of laser and radar sensors, current methods almost adopt a match strategy to estimate the dynamic parameters of a particular target with the long-term measurement collection. These kinds of data-driven methods merely consider the inherent connection between the measured characters and target dynamic patterns, and can hardly be expanded to other spacecraft when the measurement collection is insufficient. Therefore, this article presents a novel approach to interpreting multiple-station inverse synthetic aperture radar (ISAR) images for the dynamic estimation of spin spacecraft. As a unique phenomenon of radar imaging, the imaging plane of ISAR observation not only depends on the change of the relative position between the target and radar, but also changes with the spin of the target. In order to decouple the target dynamic estimation from the determination of the imaging geometry, the angular diversity of multiple-station images is employed. The proposed algorithm deduces an explicit expression of target dynamic parameters under the imaging projection model of the multiple-station observation. By utilizing the chaotic grasshopper optimization algorithm (CGOA), it determines three crucial elements of the target spin motion with a two-step optimization, including instantaneous attitude, rotation shaft and rotation speed. Simulation experiments of a typical spin spacecraft, Tiangong-I (TG-I), illustrate the feasibility of the proposed method under different motion patterns.