Total Spin Research Articles

Heisenberg-Ivanenko Nonlinear Spinor Field Equation: Spherical Symmetric Soliton-Like Solutions in Gravitational Theory

This research work deals with the concept of soliton as regular localized stable solutions of nonlinear di erential equations. In this context, exact static, spherically symmetric solutions to Heisenberg-Ivanenko nonlinear spinor field equation have been obtained in General Relativity. We opted to the static spherical symmetric metric defined in the pseudoriemannian varieties. It has been shown that the obtained solutions are regular with localized energy density and a finite total energy. In addition, the total charge and the total spin are bounded. Therefore the obtained solutions of Heisenberg-Ivanenko nonlinear spinor field equation are soliton-like configurations. Note that the e ect of gravitational field on the properties of regular localized solutions significantly depends on the symmetry of the system.

Quantum oscillations of Kondo screening phases in strong magnetic fields

We generalize the iterative diagonalization procedure adopted in method of numerical renormalization group to analyze the Kondo effect in strong magnetic fields, where the density of states for itinerary electrons at the chemical potential varies discontinuously as the magnetic field changes. We first examine phases of many-body ground states in the presence of single impurity. By investigating change of $z$-component of total spin, $\Delta S_z$, and spin-spin correlation between the impurity and conduction electrons, we find that there are three states competing for the ground state when Zeeman splitting is present. One of the states is doublet in which the impurity spin is unscreened. The other two states are Kondo screening states with $\Delta S_z=1/2$ and $\Delta S_z=1$, in which the impurity spin is partially screened and completely screened respectively. For Kondo systems with two-impurities in strong magnetic fields, we find that the interplay between the Kondo screening effect, RKKY interaction, and quantum oscillations due to Landau levels determines the ground state of the system. Combination of these three factors results in different screening scenarios for different phases in which spins of two impurities can form spin-0 or spin-1 states, while impurity spins in these phases can be either screened, partially screened, or unscreened by conduction electrons. The emergence of the ground state from these competing states oscillates with the change of magnetic field, chemical potential or inter-impurity distance. This leads to quantum oscillations in magnetization and conductivity. In particular, we find extra peak structures in longitudinal conductivity that reflect changes of Kondo screening phases and are important features to be observed in experiments. Our results provide a complete characterization of phases for Kondo effect in strong magnetic fields.

Linguistic spin in randomized controlled trials about age-related macular degeneration.

To evaluate the prevalence, type and extent of linguistic spin in randomized controlled trials (RCTs) exploring interventions in patients with age-related macular degeneration (AMD), as well as to investigate whether study variables were correlated with linguistic spin. PubMed was searched from 2011 to 2020 to identify RCTs including patients with AMD. Two authors independently assessed a total of 96 RCTs. Linear regression analyses were performed to investigate whether linguistic spin was correlated with predefined study variables. Linguistic spin was found in 61 of 96 abstracts (63.5%) and in 90 of 96 main texts (93.8%). Use of words pointing out the beneficial effect of a treatment and the use of '(statistically) significant/significance' without reporting a P-value or a 95% confidence interval (CI) were the most frequently identified categories of linguistic spin. Sample size was significantly correlated with the total linguistic spin score (95% CI 0.38-5.23, P = 0.02). A high prevalence and extent of linguistic spin in RCTs about AMD was found. We highlighted the importance of objective reporting and awareness of linguistic spin among ophthalmologists and other readers.

Effect of B substitution for Si on the electronic structure and magnetic properties of Heusler alloys Fe2CoSi1-xBx (x = 0–0.25)

A series of Fe2CoSi1-xBx (x = 0, 0.05, 0.1, 0.15, 0.2 and 0.25) Heusler alloys has been synthesized using melt-spinning method, which can help to reduce the precipitation of the secondary phase and form a highly ordered structure. The XRD patterns indicate that, when x = 0–0.1 the Fe2CoSi1-xBx melt-spun ribbons are single Heusler phases, but when x = 0.2 and 0.25 a small amount of secondary phase appears. The lattice constant decreases with increasing B content, suggesting that B mainly enters the substitutional sites of Si. The Curie temperatures TC of Fe2CoSi1-xBx alloys are all higher than 1000 K, and a 21 K increase of TC is observed as x varies from 0 to 0.25. The hysteresis loops of Fe2CoSi1-xBx alloys show soft magnetic character. Their saturation magnetizations Ms at 5 K and 300 K are similar and close to 5μB / f.u. The zero-gap half-metallic character reported for Fe2CoSi has been confirmed in present work. But with the substitution of B for Si, the Fermi level moves from the center in Fe2CoSi DOS to the left edge of the minority energy gap in Fe2CoSi0.75B0.25, which may disturb the half-metallic character when B content is high. When × = 0–0.1, the Ms at 5 K of Fe2CoSi1-xBx agree well with the calculated total spin moments, but when the B content is high, especially when x = 0.2 and 0.25, a deviation between the experimental and theoretical results is observed, which is related to the secondary phase in these samples.

Oscillating spin Hall effect from polaron transport in organic chains

The polaron dynamics in organic ladders is calculated in the presence of electron-lattice and spin-orbit couplings (SOCs), employing an extended Su-Schrieffer-Heeger (SSH) model and a nonadiabatic dynamics method. The time-dependent total charge and spin in the chains is averaged over initial polaron states with spins up and down. This average reveals a strong oscillating spin Hall effect (SHE). We show the necessity of all terms in the SSH Hamiltonian for the SHE, including intrachain and interchain hopping as well as intrachain and interchain SOC. The large and rapidly oscillating behavior of the SHE is verified to originate from the existence of polarons by comparison with the case of rigid chains without polarons. We attribute the enhancement of the SHE to skew scattering off transient deformations of the chains. Spectral analysis exhibits three dominant parts in the Fourier-transformed spin Hall signal. The high-frequency part is associated with the pure spin-flip dynamics due to SOC, while the low-frequency parts, which are also observed in the charge response, are related to the intrinsic electron transfer between the chains and the appearance of polarons, respectively. In this paper, we reveal the distinct properties of the dynamical SHE in organics dominated by polaron transport.

Linear response for pseudo-Hermitian Hamiltonian systems: Application to PT -symmetric qubits

Motivated by the recent advances in modelling the pseudo-Hermitian Hamiltonian (pHH) systems using superconducting qubits we analyze their quantum dynamics subject to a small time-dependent perturbation. In particular, We develop the linear response theory formulation suitable for application to various pHH systems and compare it to the ones available in the literature. We derive analytical expressions for the generalized temporal quantum-mechanical correlation function $C(t)$ and the time-dependent dynamic susceptibility $\chi(t) \propto \text{Im} ~C(t)$. We apply our results to two \textit{PT}-symmetric non-Hermitian quantum systems: a single qubit and two unbiased/biased qubits coupled by the exchange interaction. For both systems we obtain the eigenvalues and eigenfunctions of the Hamiltonian, identify \textit{PT}-symmetry unbroken and broken quantum phases and quantum phase transitions between them. The temporal oscillations of the dynamic susceptibility of the qubits polarization ($z$-projection of the total spin), $\chi(t)$, relate to {\it ac} induced transitions between different eigenstates and we analyze the dependencies of the oscillations frequency and the amplitude on the gain/loss parameter $\gamma$ and the interaction strength $g$. Studying the time dependence of $\chi(t)$ we observe different types of oscillations, i.e. undamped, heavily damped and amplified ones, related to the transitions between eigenstates with broken (unbroken) $PT$-symmetry. These predictions can be verified in the microwave transmission experiments allowing controlled simulation of the pHH systems.

Ab initio prediction of half-metallicity in the NaMnZ2 (Z = S, Se, Te) ternary layered compounds

Motivated by recent theoretical studies predicting half-metallicity in some ternary manganese chalcogenides, first-principles calculations based on spin-polarized density functional theory (DFT) are applied to investigate the structural, elastic, electronic and magnetic properties of the ternary layered compounds NaMnZ2 (Z = S, Se, Te). We assume for all compounds the experimentally determined, in the case of NaMnSe2 and NaMnTe2 compounds, noncentrosymmetric trigonal structure (space group P3m1; no. 156). The analysis of spin-polarized band structures and of the diagrams of density of states reveals the half-metallic character of the considered materials. We find that the strong spin polarization of the d orbitals of the manganese atoms is at the origin of the ferromagnetism of these compounds with a total magnetic moment per formula unit of 4μB. The studied compounds show a Slater-Pauling behavior and the total spin magnetic moment per cell (Mt) evolves with the total number of valence electrons (Zt) according to the lawMt=(Zt−22)μB. The calculated values of the minority-spin energy gap (Eg) and of the half-metallic gap (EHM) for the explored materials show that they are promising compounds for spintronic applications.

Contact interaction analysis of octet baryon axial-vector and pseudoscalar form factors

Octet baryon axial, induced pseudoscalar, and pseudoscalar form factors are computed using a symmetry-preserving treatment of a vector$\,\times\,$vector contact interaction (SCI), thereby unifying them with an array of other baryon properties and analogous treatments of semileptonic decays of pseudoscalar mesons. The baryons are treated as quark--plus--interacting-diquark bound states, whose structure is obtained by solving a Poincar\'e-covariant Faddeev equation. The approach is marked by algebraic simplicity, involves no free parameters, and since it is symmetry preserving, all consequences of partial conservation of the axial current are manifest. It is found that SCI results are consistent with only small violations of SU$(3)$-flavour symmetry, an outcome which may be understood as a dynamical consequence of emergent hadron mass. The spin-flavour structure of the Poincar\'e-covariant baryon wave functions is expressed in the presence of both flavour-antitriplet scalar diquarks and flavour-sextet axialvector diquarks and plays a key role in determining all form factors. Considering neutral axial currents, SCI predictions for the flavour separation of octet baryon axial charges and, therefrom, values for the associated SU$(3)$ singlet, triplet, and octet axial charges are obtained. The results indicate that at the hadron scale, $\zeta_{\cal H}$, valence degrees-of-freedom carry roughly 50% of an octet baryon's total spin. Since there are no other degrees-of-freedom at $\zeta_{\cal H}$, the remainder may be associated with quark+diquark orbital angular momentum.

Evaporation of water and urea solution in a magnetic field; the role of nuclear isomers

HypothesisOrtho and para water are the two nuclear isomers where the hydrogen protons align to give a total nuclear spin of 1 or 0. The equilibrium ratio of 3:1 is established slowly in freshly evaporated water vapour while the isomers behave distinct gasses, with their own partial pressures. Magnetic-field-induced ortho ⟷ para transformations are expected to alter the evaporation rate. ExperimentEvaporation from beakers of deionized water and a 6 M solution of urea is monitored simultaneously for periods from 1 to 60 h with and without a 500 mT magnetic field, while logging the ambient temperature and humidity. Balances with the two beakers are shielded in the same Perspex container. Many runs have been conducted over a two-year period. FindingsThe evaporation rate of water is found to increase by 12 ± 7% of in the field but that of water with dissolved urea decreases by 28 ± 6%. Two effects are at play. One is dephasing of the Larmor precession of adjacent protons on a water molecule in a field gradient, which tends to equalize the isomer populations. The other is Lorentz stress on the moving charge dipole, which can increase the proportion of the ortho isomer. From analysis of the time and field dependence of the evaporation, we infer that the ortho fraction is 39 ± 1% in fresh vapour from water and 60 ± 5% in fresh vapour from urea.

Cu12@Au30Ag12: a magnetic pentakis icosidodecahedron molecule with core-shell configuration.

A 54-atom trimetallic core-shell Cu12@Au30Ag12 molecule has been identified by using first-principles calculations. This molecule with Ih symmetry consists of an icosahedral 12-atom Cu core (Cu12) coated by a pentakis icosidodecahedral 42-atom Au-Ag shell (Au30Ag12) composed of an icosidodecahedral Au30 and an icosahedral Ag12. Both the molecular dynamics simulations and vibrational frequency analysis demonstrate the high stability of Cu12@Au30Ag12. The analyses for electronic properties indicate that there exists spd hybridization which is crucial to maintain the geometrical configuration of Cu12@Au30Ag12. Moreover, a total spin magnetic moment of Cu12@Au30Ag12 is found to be 4 µB, which chiefly arises from the 6s states of Au atoms. A new type of sugar gourd-like [Cu12@Au30Ag11]n nanowire is also proposed; the results demonstrate that the nanowire exhibits metallic and magnetic behaviors. The magnetic Cu12@Au30Ag12 molecule and [Cu12@Au30Ag11]n nanowire can be promising candidates of novel magnetic nanomaterials and nanodevices.

Deterministic preparation of supersinglets with collective spin projections

We introduce a procedure to generate supersinglets, the multipartite generalization of angular momentum singlet states. A supersinglet is defined as a total spin zero state consisting of $N$ spin-$j$ particles. They are highly entangled and have zero spin variance in any direction, and as such are potentially useful for quantum metrology. Our scheme is based on projective measurements that measure the collective spin of the whole spin ensemble. A local unitary rotation is applied conditionally on the measurement outcome, such as to maximize the probability of obtaining spin zero on the subsequent measurement. The sequence is repeated in the $z$ and $x$ basis until convergence is obtained towards the supersinglet state. Our sequence works regardless of the initial state, and no postselection is required. Due to the use of strong projective measurements, very fast convergence towards zero spin variance is obtained. We discuss an example implementation using quantum nondemolition measurements in atomic ensembles, and perform numerical simulations to demonstrate the procedure.

Spin-textures of medium-body boson systems with trapped spin-f cold atoms

The spin-textures of bound medium-body systems with spin-mathfrak {f} atoms (mathfrak {f}ge 3) have been studied. The Hamiltonian is assumed to be dominated by the two-body interaction favoring parallel spins. The system with particle number N=8 and mathfrak {f}=3 is first chosen, and the Hamiltonian is exactly diagonalized by using Fock-states as basis-states, thereby all the eigenenergies and eigenstates are obtained and a detailed analysis is made. Then the cases with N=13 and mathfrak {f}=4 are further studied. Since the total spin S is conserved, the eigenstates having the same S form an S-group. Let the lowest (highest) energy state of an S-group be called a bottom-state (top-state). We found that all the bottom-states are bipartite product states with constituent states describing fully polarized subsystems containing N_1 and N_2 (le N_1) particles, respectively. For two bottom-states different in N_2, the one with a larger N_2 is higher. For two having the same N_2, the one with a smaller S is higher. Whereas all the top-states are found to be essentially a product state of the pairs, in each pair the two spins are coupled to lambda if the strength of the lambda-channel is more repulsive than the others. For the states belonging to an S-group, the higher one would contain more pieces. As the energy goes up, larger pieces (those containing more than two particles) will disappear.

Controlling Antiferromagnetic Magnon Polarization by Interfacial Exchange Interaction

We demonstrate highly efficient control of antiferromagnetic (AFM) magnon spins by the interfacial exchange interaction in heterostructures of ferrimagnetic yttrium iron garnet (YIG) and AFM ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$. At low temperatures, ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ is antiferromagnetically ordered. The interfacial exchange interaction exerted by YIG lifts the degeneracy between the AFM magnon modes in ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$, resulting in a net spin polarization and a spin current dominated by left-handed magnons, even at zero magnetic field, which is detected by the spin Seebeck effect with a 5-nm-thick $\mathrm{Pt}$ film. In the AFM magnon-dominated region, even if the magnetic field is not sufficiently strong to induce the spin-flop transition in ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$, the total spin Seebeck signal polarity flips when the YIG magnetization switches. It clearly indicates that the ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ magnon polarization is controlled by YIG magnetization through the interfacial exchange interaction. The demonstration of the efficient control of AFM magnon polarization opens a pathway to manipulate AFM magnon quantum states using FM-AFM heterostructures.

Number of states with given spin I and isospin T for n fermions in a j orbit* *Supported by the National Natural Science Foundation of China (11975151, 11961141003) and the MOE Key Lab for Particle Physics, Astrophysics and Cosmology for financial support

In this study, we investigate formulas of the number of states with a given total spin I and isospin T for n nucleons in a single-j shell denoted by . Talmi's recursion formulas for the number of states with a given z-axis projection of total spin are generalized by further considering the isospin couplings and are applied to derive explicit formulas of .

Domain-wall dynamics driven by thermal and electrical spin-transfer torque

According to spin Seebeck effect, a thermal spin current will be produced when a temperature gradient is applied to the metallic ferromagnet. Similar to the electrical spin transfer torque (ESTT) induced by spin-polarized current, there is also a thermal spin transfer torque (TSTT) caused by the thermal spin current, which can be attributed to the s-d interaction between the conduction electrons and the local magnetization. In this paper, the generalized analytical expressions of thermal spin current and TSTT are derived based on the spinor Boltzmann equation (SBE) under the local equilibrium approximation. This generalized TSTT has different terms compared to the previous phenomenological form, and the phenomenological coefficients can be determined theoretically within our framework. Combined with the SBE under the applied electric field and temperature gradient, we solve the Landau-Lifshitz-Gilbert-Levy equation to study the domain wall (DW) motion driven by the ESTT and TSTT. We investigated the temperature-dependent DW motion, the total spin torque, and TSTT in permalloys. We found that the velocity of the DW can be promoted by increasing temperature and temperature gradient, which provide a path to effectively utilize the Joule heating in spintronics devices.

Mechanisms of Complete Dissociation of CO2 on Iron Clusters.

Dissociation of CO2 on iron clusters was studied by using semilocal density functional theory and basis sets of triple-zeta quality. Fe2 , Fe4 , and Fe16 clusters were selected as the representative host clusters. When searching for isomers of Fen CO2 , n=2, 4 and 16 corresponding to carbon dioxide attachment to the host clusters, its reduction to O and CO, and to the complete dissociation, it was found that the total spin magnetic moments of the lowest energy states of the isomers are often quenched with respect to those of initial reagents Fen +CO2 . Dissociation pathways of the Fe2 +CO2 , Fe4 +CO2 , and Fe16 +CO2 reactions contain several transition states separated by the local minima states; therefore, a natural question is where do the spin flips occur? Since lifetimes of magnetically excited states were shown to be of the order of 100 fs, the search for the CO2 dissociation pathways was performed under the assumption that magnetic deexcitation may occur at the intermediate local minima. Two dissociation pathways were obtained for each Fen +CO2 reaction using the gradient-based methods. It was found that the Fe2 +CO2 reaction is endothermic with respect to both reduction and complete dissociation of CO2 , whereas the Fe4 +CO2 and Fe16 +CO2 reactions are exothermic to both reduction and complete dissociation of carbon dioxide. The CO2 reduction was found to be more favorable than its complete dissociation in the Fe4 case.

Spin and orbital magnetism of exohedral fullerene doped with single transition metal atom (Sc-Ni): A relativistic density functional theory study

Relativistic density functional theory calculations have been implemented to study the structural configurations, electronic and magnetic properties of exohedral 3d transition metal atoms doping on C60 fullerene (TM-C60) by a full potential local orbital method. The calculated binding energies revealed that the TM-C60 molecules are energetically stable in all adsorption sites. We also found that the TM-doped exohedral C60 complexes are more reactive than pure C60 fullerene. The spin and orbital magnetic moments were also determined. We have indicated that in all of the five adsorption sites, exohedral TM-C60 molecules (except for Ni-C60) are magnetized. Our magnetic calculations show that the total spin magnetic moments of TM-C60 molecules mainly come from the TM atoms. We found that the spin magnetic moments of adsorbed TM atoms in exohedral doping C60 fullerene from Sc to Mn (HH adsorption site) and for Sc to Cr (HP and P adsorption sites) are greater than their free states. Our calculations suggest that exohedral doping 3d TM-C60 complexes can almost maintain spin magnetic moments. We have indicated that the magnetic properties of exohedral TM-C60 molecules change in the presence of spin–orbit coupling. Significant orbital contributions to magnetic moments are recognized in these configurations while the spin moments are unaffected. We found that Co in exohedral doping of C60 fullerene shows a robust orbital moment in all the five adsorption sites.

Small-scale structure in vector dark matter

We investigate the differences in the small-scale structure of vector dark matter (VDM) and scalar dark matter (SDM) using 3+1 dimensional simulations of single/mul­ticomponent Schrödinger-Poisson system. We find that the amount of wave interference, core-to-halo mass ratio (and its scatter), spin of the core, as well as the shape of the central regions of dark matter halos can distinguish VDM and SDM. Starting with a collection of idealized halos (self-gravitating solitons) as an initial condition, we show that the system dynamically evolves to an approximately spherically symmetric configuration that has a core surrounded by a halo of interference patterns in the mass density. In the vector case, the central soliton in less dense and has a smoother transition to an r -3 tail compared to the scalar case. As compared to SDM, wave interference in VDM is ∼ 1/√3 times smaller, resulting in fewer low and high density regions, and more diffuse granules in the halo. The ratio of VDM core mass to the total halo mass is lower than that in SDM, with a steeper dependence on the total energy of the system and a slightly larger scatter. Finally, we also initiate a study of the evolution of intrinsic spin angular momentum in the VDM case. We see a positive correlation between the total intrinsic spin in the simulation and the spin of the final central core, with significant scatter. We see large intrinsic spin in the core being possible even with vanishing amounts total angular momentum in the initial conditions (at least instantaneously). Our results point towards the possibility of distinguishing VDM from SDM using astrophysical and terrestrial observations.

Identification of Ge═O Double Bonds in Planar MnGe3O and MnGe4O Clusters: Anion Photoelectron Spectroscopy and Ab Initio Calculations.

The structures, chemical bonding, and magnetic properties of MnGe3O-/0 and MnGe4O-/0 are investigated by photoelectron spectroscopy and ab initio calculations. The experimental vertical electron detachment energies of MnGe3O- and MnGe4O- are measured to be 2.06 ± 0.04 and 2.64 ± 0.04 eV, respectively. The structures of MnGe3O-/0 and MnGe4O-/0 can be viewed as evolved from quadrilateral MnGe3 or tetrahedral MnGe3. It is found that both MnGe3O- and MnGe3O have Cs symmetric planar structures with an O atom attached to quadrilateral MnGe3. The structure of MnGe4O- is nonplanar with an O atom and an additional Ge atom attached to tetrahedral MnGe3, while that of MnGe4O is planar with an O atom and an additional Ge atom attached to quadrilateral MnGe3. Chemical bonding analyses reveal the existence of Ge═O double bonds in MnGe3O and MnGe4O. Magnetic property analyses suggest that MnGe3O and MnGe4O are ferromagnetic with total spin magnetic moments of 5 μB.

EPR-active dimer centers with S=1 in α-Al2O3 single crystals irradiated by fast neutrons

Corundum (α-Al2O3) possesses a number of unique properties, including high tolerance to harsh radiation environment. Material functionality is strongly affected by radiation-induced structural defects, single interstitial-vacancy Frenkel pairs and their aggregates. Three novel paramagnetic two-electron defects with total spin S = 1 have been revealed in fast neutron irradiated α-Al2O3 single crystals by means of the EPR method. Analysis of the EPR characteristics of these defects allows to conclude that the main novel D1 defect (initial concentration after irradiation about 2.8 × 1016 cm−3) is oriented along one of three equivalent b crystal axes, that connect two adjacent anion sites of oxygen triangles on the base corundum plane. The D1 defect is ascribed to the F22+ center (two adjacent single-charged oxygen vacancies), while the D2 and D3 have the same dimer structure with an additional defect in their vicinity. The suggested defect structure is supported by pulse annealing of the EPR signal of relevant defects: defect concentration dependence contains a rising stage at 500–630 K, while complete thermal destruction due to the recombination with complementary oxygen interstitials occurs by 720–750 K. Such behavior qualitatively coincides with earlier studied thermal annealing of the F22+ center optical absorption in neutron-irradiated corundum.