Contribution Of Orbital Angular Momentum Research Articles

Flavor asymmetry of light sea quarks in proton: a light-front spectator model

We formulate a light-front spectator model for the proton that incorporates the presence of light sea quarks. In this particular model, the sea quarks are seen as active partons, whereas the remaining components of the proton are treated as spectators. The proposed model relies on the formulation of the light-front wave function constructed by the soft wall AdS/QCD. The model wave functions are parameterized by fitting the unpolarized parton distribution functions of light sea quarks from the CTEQ18 global analysis. We then employ the light-front wave functions to obtain the sea quarks generalized parton distribution functions, transverse momentum dependent parton distributions, and their asymmetries, which are accessible in the upcoming Electron-Ion-Colliders. We investigate sea quarks’ spin and orbital angular momentum contributions to the proton spin.

Tailoring Photoinduced Nonequilibrium Magnetizations in In2Se3 Bilayers

AbstractMagnetization generation and accumulation in intrinsically nonmagnetic materials is one of the key routes to various exotic applications, especially realizing fast information storage and memory devices. Among the various approaches for magnetization injection, light irradiation is advantageous for its noncontacting and non‐invasive nature, and has been receiving great attention during the past few decades. In the current work, a quadratic response theory and first‐principles calculations are applied to reveal photoinduced magnetization in recently discovered 2D In2Se3 bilayers. The ferroelectric In2Se3 bilayers can be (meta‐) stabilized in versatile stacking patterns, exhibiting largely tunable electronic band structure, and optical feature. Hence, it is suggested that under circularly polarized light illumination, the system can show different photoinduced magnetization responses with large contrast in different stacking patterns. The magnetizations are composed by both spin and orbital angular momentum contributions, which can reach as large as 1μB under a laser with intermediate intensity (≈109 W cm–2). This magnitude can be easily observed and furthermore manipulated in the state‐of‐the‐art experimental techniques. The proposal suggests a candidate material platform to explore the interplay among spintronics, orbitronics, nonlinear optics, and ferroelectrics in a single platform.

Molecular and Electronic Structures of a Series of Dinuclear CoII Complexes Varied by Exogeneous Ligands: Influence of π‐Bonding on Redox Potentials

AbstractFour dinuclear CoII complexes have been synthesized and structurally characterized with the dinucleating ligand susan (susan=4,7‐dimethyl‐1,1,10,10‐tetra(2‐pyridylmethyl)‐1,4,7,10‐tetraazadecane) varying in the exogeneous ligands: [(susan){CoII(CH3CN)2}2](PF6)4, [(susan){CoIICl}2](ClO4)2, [(susan){CoIIBr}2](ClO4)2, and [(susan){CoII(μ‐OH)CoII}](ClO4)3. The CoII ions are six‐coordinate with CH3CN ligands and five‐coordinate with anionic ligands. The electronic absorption spectra reflect the differences in the electronic structures, not only between the six‐ and five‐coordinate complexes, but also between the five‐coordinate complexes. These variations are also reflected in the magnetic properties with the highest orbital angular momentum contribution in six‐coordinate [(susan){CoII(CH3CN)2}2](PF6)4. The lower symmetry in the five‐coordinate complexes reduces the orbital angular momentum contribution. The hydroxo‐bridged complex [(susan){CoII(μ‐OH)CoII}](ClO4)3 exhibits an additional antiferromagnetic interaction. The electrochemical characterization reveals that the π‐acceptor ligand CH3CN facilitates not only reduction from CoII to CoI but also oxidation to CoIII, while the π‐donor ligands Br−, Cl−, and μ‐OH− impede both reduction to CoI and oxidation to CoIII. [(susan){CoII(CH3CN)2}2](PF6)4 and [(susan){CoIICl}2](ClO4)2 show electrocatalytic proton reduction at a potential of ≈−1.9 V vs Fc+/Fc that is associated with a ligand‐centered reduction.

Magnetism and spin dynamics in room-temperature van der Waals magnet Fe5GeTe2

Two-dimensional van der Waals (vdWs) materials have gathered a lot of attention recently. However, the majority of these materials have Curie temperatures that are well below room temperature, making it challenging to incorporate them into device applications. In this work, we synthesized a room-temperature vdW magnetic crystal Fe5GeTe2 with a Curie temperature T K, and studied its magnetic properties by vibrating sample magnetometry (VSM) and broadband ferromagnetic resonance (FMR) spectroscopy. The experiments were performed with external magnetic fields applied along the c-axis (H c) and the ab-plane (H ab), with temperatures ranging from 300 to 10 K. We have found a sizable Landé g-factor difference between the H c and H ab cases. In both cases, the Landé g-factor values deviated from g = 2. This indicates contribution of orbital angular momentum to the magnetic moment. The FMR measurements reveal that Fe5GeTe2 has a damping constant comparable to Permalloy. With reducing temperature, the linewidth was broadened. Together with the VSM data, our measurements indicate that Fe5GeTe2 transitions from ferromagnetic to ferrimagnetic at lower temperatures. Our experiments highlight key information regarding the magnetic state and spin scattering processes in Fe5GeTe2, which promote the understanding of magnetism in Fe5GeTe2, leading to implementations of Fe5GeTe2 based room-temperature spintronic devices.

Two-Coordinate, Nonlinear Vanadium(II) and Chromium(II) Complexes of the Silylamide Ligand–N(SiMePh2)2: Characterization and Confirmation of Orbitally Quenched Magnetic Moments in Complexes with Sub-d5 Electron Configurations

The two-coordinate metal amide complexes V{N(SiMePh2)2}2 (1) and Cr{N(SiMe2Ph)2}2 (2) were synthesized by reaction of two equivalents of LiN(SiMePh2)2 with VI2(THF)4 or CrCl2(THF)2 in n-hexane. Their crystal structures showed that they have bent coordination, N-V-N = 137.0(4)°, N-Cr-N = 139.19(5)°, at the metals. The vanadium complex (1) displayed no tendency to isomerize as previously observed for some V(II) amido complexes. Curie fits of SQUID magnetic measurements afforded magnetic moments of 3.36 (1) and 4.68 (2) μB, consistent with high-spin configurations. These values are lower than the spin-only values of 3.88 and 4.90 μB expected for d3 and d4 complexes, suggesting a significant unquenched orbital angular momentum contribution to the overall moment, which is lower as a result of the positive spin-orbit coupling constants.

A Molecular Crystal Shows Multiple Correlated Magnetic and Ferroelectric Switchings

Simultaneous control of the magnetic and electric properties of materials is crucial for their application in next-generation memory and sensor devices. Herein, we report a single-crystal Co(II) co...

Magnetic susceptibility of QCD matter and its decomposition from the lattice

We determine the magnetic susceptibility of thermal QCD matter by means of first principles lattice simulations using staggered quarks with physical masses. A novel method is employed that only requires simulations at zero background field, thereby circumventing problems related to magnetic flux quantization. After a careful continuum limit extrapolation, diamagnetic behavior (negative susceptibility) is found at low temperatures and strong paramagnetism (positive susceptibility) at high temperatures. We revisit the decomposition of the magnetic susceptibility into spin- and orbital angular momentum- related contributions. The spin term — related to the normalization of the photon lightcone distribution amplitude at zero temperature — is calculated non-perturbatively and extrapolated to the continuum limit. Having access to both the full magnetic susceptibility and the spin term, we calculate the orbital angular momentum contribution for the first time. The results reveal the opposite of what might be expected based on a free fermion picture. We provide a simple parametrization of the temperature- and magnetic field-dependence of the QCD equation of state that can be used in phenomenological studies.

Covalency and magnetic anisotropy in lanthanide single molecule magnets: the DyDOTA archetype.

Lanthanide ions when complexed by polyamino-polycarboxylate chelators form a class of compounds of paramount importance in several research and technological areas, particularly in the fields of magnetic resonance and molecular magnetism. Indeed, the gadolinium derivative is one of the most employed contrast agents for magnetic resonance imaging while the dysprosium one belongs to a new generation of contrast agents for T2-weighted MRI. In molecular magnetism, Single Molecule Magnets (SMMs) containing lanthanide ions have become readily popular in the chemistry and physics communities since record energy barriers to the reversal of magnetization were reported. The success of lanthanide complexes lies in their large anisotropy due to the contribution of the unquenched orbital angular momentum. However, only a few efforts have been made so far to understand how the f-orbitals can be influenced by the surrounding ligands. The outcomes have been rationalized using mere electrostatic perturbation models. In the archetype compound [Na{Dy(DOTA) (H2O)}]·4H2O (Na{DyDOTA}·4H2O) an unexpected easy axis of magnetization perpendicular to the pseudo-tetragonal axis of the molecule was found. Interestingly, a dependency of the orientation of the principal magnetization axis on the simple rotation of the coordinating apical water molecule (AWM) - highly relevant for MRI contrast - around the Dy-OAWM bond was predicted by ab initio calculations, too. However, such a behaviour has been contested in a subsequent paper justifying their conclusions on pure electrostatic assumptions. In this paper, we want to shed some light on the nature of the subtle effects induced by the water molecule on the magnetic properties of the DyDOTA archetype complex. Therefore, we have critically reviewed the structural models already published in the literature along with new ones, showing how the easy axis orientation can dangerously depend on the chosen model. The different computed behaviors of the orientation of the easy axis of magnetization have been rationalized as a function of the energy gap between the ground and the first excited doublet. Magneto-structural correlations together with a mapping of the electrostatic potential generated by the ligands around the Dy(iii) ion through a multipolar expansion have also been used to evidence and quantify the covalent contribution of the AWM orbitals.

Experimental Observation of Hidden Berry Curvature in Inversion-Symmetric Bulk 2H-WSe_{2}.

We investigate the hidden Berry curvature in bulk 2H-WSe_{2} by utilizing the surface sensitivity of angle resolved photoemission (ARPES). The symmetry in the electronic structure of transition metal dichalcogenides is used to uniquely determine the local orbital angular momentum (OAM) contribution to the circular dichroism (CD) in ARPES. The extracted CD signals for the K and K^{'} valleys are almost identical, but their signs, which should be determined by the valley index, are opposite. In addition, the sign is found to be the same for the two spin-split bands, indicating that it is independent of spin state. These observed CD behaviors are what are expected from Berry curvature of a monolayer of WSe_{2}. In order to see if CD-ARPES is indeed representative of hidden Berry curvature within a layer, we use tight binding analysis as well as density functional calculation to calculate the Berry curvature and local OAM of a monolayer WSe_{2}. We find that measured CD-ARPES is approximately proportional to the calculated Berry curvature as well as local OAM, further supporting our interpretation.

Humblet's angular momentum decomposition applied to radiation torque on metallic spheres using the Hagen–Rubens approximation

When a circularly polarized electromagnetic wave is scattered by an isotropic sphere, Humblet's decomposition from 1943 is helpful for understanding why the axial projection of the spin-angular momentum gives incomplete information concerning the total radiated angular momentum. Humblet asserted that some field angular momentum is orbital angular momentum (OAM). This distinction, applied here to Mie scattering, gives insight into why classical electromagnetic radiation torque is proportional to absorbed power for isotropic spheres. It also reveals the direct measurability (from Stokes parameters) of spin contributions to the radiated angular momentum. This approach is applied to metallic spheres in circularly polarized illumination modeled with Lorenz–Mie theory using the Hagen–Rubens approximation (1903) in which the real and imaginary components of the sphere's refractive index are equal in magnitude. That approximation is often useful for terahertz and lower frequencies. It was helpful to compare a spin efficiency factor Qspin with the canonical scattering efficiency factor Qsca for varying sphere sizes at a fixed frequency. A small-size limiting case Qsca/Qspin = 2 is recovered associated with a common interpretation of electric dipole-related torque. For larger sizes, the OAM contribution increases giving Qsca/Qspin > 2. Van de Hulst's scattering calculations for metal spheres are also reproduced.Dedicated in memory of Seattle Pacific University Professor James H. Crichton (1937–1999).

Transition magnetic moments of decuplet to octet baryons in the chiral constituent quark model

In light of the developments of the chiral constituent quark model (χCQM) in studying low energy hadronic matrix elements of the ground-state baryons, we extend this model to investigate their transition properties. The magnetic moments of transitions from the decuplet to octet baryons are calculated with explicit valence quark spin, sea quark spin and sea quark orbital angular momentum contributions. Since the experimental data is available for only a few transitions, we compare our results with the results of other available models. The implications of other complicated effects such as chiral symmetry breaking and SU(3) symmetry breaking arising due to confinement of quarks are also discussed.

Synthesis, Structure, and Bonding for Bis(permethylpentalene)diiron.

The synthesis of the first homoleptic double metallocene complex of iron, Fe2Pn*2 (Pn* = permethylpentalene, C8Me6) is described. The structural and electronic properties of Fe2Pn*2 have been characterized by NMR and EPR spectroscopy, single crystal X-ray diffraction, magnetic measurements, cyclic voltammetry, and DFT calculations. Fe2Pn*2 adopts a Ci symmetry in the solid state with a Fe-Fe distance of 2.3175(9) Å, slightly lower than the sum of radii in metallic iron. Magnetic measurements in solution, and of the solid phase between 60 and 300 K, indicate that Fe2Pn*2 is a triplet (S = 1) paramagnet, with effective magnetic moments (μeff) of 3.4 and 3.48 μB, respectively. DFT calculations indicate the origin of this high magnetic moment is likely to be unquenched orbital angular momentum contributions from two SOMOs which have metal d character. Cyclic voltammetry studies demonstrate that Fe2Pn*2 can access four charge states (-1, 0, +1, +2).

Quantum numbers of theX(3872)state and orbital angular momentum in itsρ0J/ψdecay

Angular correlations in $B^+\to X(3872) K^+$ decays, with $X(3872)\to \rho^0 J/\psi$, $\rho^0\to\pi^+\pi^-$ and $J/\psi \to\mu^+\mu^-$, are used to measure orbital angular momentum contributions and to determine the $J^{PC}$ value of the $X(3872)$ meson. The data correspond to an integrated luminosity of 3.0 fb$^{-1}$ of proton-proton collisions collected with the LHCb detector. This determination, for the first time performed without assuming a value for the orbital angular momentum, confirms the quantum numbers to be $J^{PC}=1^{++}$. The $X(3872)$ is found to decay predominantly through S wave and an upper limit of $4\%$ at $95\%$ C.L. is set on the fraction of D wave.

Electroproduction of theN*(1535)nucleon resonance in QCD

Following the 12 GeV upgrade, a dedicated experiment is planned with the Hall B CLAS12 detector at Jefferson Lab, with the aim to study electroproduction of nucleon resonances at high photon virtualities up to $Q^2 = 12$ GeV$^2$. In this work we present a QCD-based approach to the theoretical interpretation of these upcoming results in the framework of light-cone sum rules that combine perturbative calculations with dispersion relations and duality. The form factors are thus expressed in terms of $N^\ast(1535)$ light-front wave functions at small transverse separations, called distribution amplitudes. The distribution amplitudes can therefore be determined from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations. The results of the corresponding next-to-leading order calculation are presented and compared with the existing data. We find that the form factors are dominated by the twist-four distribution amplitudes that are related to the $P$-wave three-quark wave functions of the $N^\ast(1535)$, i.e. to contributions of orbital angular momentum.

Direct observation of high-spin states in manganese dimer and trimer cations by x-ray magnetic circular dichroism spectroscopy in an ion trap.

The electronic structure and magnetic moments of free Mn2 (+) and Mn3 (+) are characterized by 2p x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap that is coupled to a synchrotron radiation beamline. Our results directly show that localized magnetic moments of 5 μB are created by 3d(5)((6)S) states at each ionic core, which are coupled ferromagnetically to form molecular high-spin states via indirect exchange that is mediated in both cases by a delocalized valence electron in a singly occupied 4s derived antibonding molecular orbital with an unpaired spin. This leads to total magnetic moments of 11 μB for Mn2 (+) and 16 μB for Mn3 (+), with no contribution of orbital angular momentum.

Stern-Gerlach Experiments on Fe@Sn12: Magnetic Response of a Jahn–Teller Distorted Endohedrally Doped Molecular Cage Cluster

The magnetic response of the Fe@Sn12 cluster is investigated by magnetic beam deflection experiments. In contrast to Mn@Sn12, the molecular beam of this cluster is deflected almost exclusively toward increasing field, also at low temperatures, supposable due to Jahn–Teller induced distortions of the tin cage. The magnitude of the magnetic dipole moment is extracted from the shift of the beam profile and provides evidence for a (partially quenched) contribution of electronic orbital angular momentum to the magnetic dipole moment.

Quark Spin-Orbit Correlations

The proton spin puzzle issue focused the attention on the parton spin and orbital angular momentum contributions to the proton spin. However, a complete characterization of the proton spin structure requires also the knowledge of the parton spin-orbit correlation. We showed that this quantity can be expressed in terms of moments of measurable parton distributions. Using the available phenomenological information about the valence quarks, we concluded that this correlation is negative, meaning that the valence quark spin and kinetic orbital angular momentum are, in average, opposite. The quark spin-orbit correlation can also be expressed more intuitively in terms of relativistic phase-space distributions, which can be seen as the mother distributions of the standard generalized and transverse-momentum dependent parton distributions. We present here for the first time some examples of the general multipole decomposition of these phase-space distributions.

An enhancement ZT and spin state transition of Ca3Co4O9 with Pb doping

We reported the structural, electrical, thermal and magnetic properties of Pb-doped Ca3Co4O9 in the range of 300–5K. DTA analysis showed that the stability of the Ca3Co4O9 was increased with Pb doping. According to XRD analysis, it is found that Pb ions were successfully doped in the Ca3Co4O9 structure. The temperature of resistivity minima, Tmin, increased by increasing the Pb doping level and it is seen that incommensurate spin density wave state becomes more stable with Pb doping. The enhancement of thermopower was explained that Pb doping in Ca sites caused a decrease of Co4+ fraction such that Co4+ ions transformed into Co3+ or Co2+. The room temperature ZT value of the polycrystalline sample reaches about 16 times larger value than that of the un-doped polycrystalline sample which is the promising candidate for high temperatures in the thin film applications.According to magnetic susceptibility measurement, the increase of effective magnetic moment by Pb concentration was explained by spin state transition of Co3+ from low spin to intermediate spin and high spin state together with some orbital angular momentum contribution which comes from 5T2 term due to a decrease of the ligand field splitting energy.

Nuclear magnetic moments for J π = 2 1 + state of 10Be with ab initio Monte Carlo shell model calculation

The magnetic moment of 2 1 + state for 10Be are calculated and investigated in terms of single particle orbits for protons and neutrons under the framework of ab initio Monte Carlo shell model method in an e max = 3 model space. The reduced matrix elements of orbital and spin angular momentum are evaluated. It is found that the orientations of orbital angular momentum in different single particle orbits are consistent. Conversely, the orientations of spin in different single particle orbits tend to be chaotic. The nuclear magnetic moment of 2 1 + state for 10Be is obtained as 1.006 µ N and is discussed in regards to the contribution of orbital and spin angular momentum both for protons and neutrons. The corresponding g-factor is also given.

Transverse single spin asymmetry measurements at STAR

Transverse single spin asymmetries AN are expected to be sensitive to par-ton polarization and orbital angular momentum contributions to the nucleon spin. Significantly large AN has been observed in different collision systems such as semi-inclusive deep inelastic scattering (SIDIS) and polarized proton-proton (pp) collisions, indicating a dominant contribution of partonic interactions in the non-perturbative regime. Therefore it’s critical to measure AN in various channels of polarized pp collisions in order to complement SIDIS data and to constrain theoretical models. We report STAR asymmetry measurements on mid-rapidity hadron-jet and di-hadron correlations at √s = 200 GeV and forward rapidity inclusive hadron production at √s = 500 GeV polarized pp collisions.