Spin-orbit Term Research Articles

Spectrum of strange singly charmed baryons in the constituent quark model

Excited states masses of the strange singly charmed baryons are calculated using the non-relativistic approach of hypercentral Constituent Quark Model (hCQM). The hyper-Coulomb plus screened potential is used as a confinement potential with the first order correction. The spin-spin, spin-orbit and spin-tensor interaction terms are included perturbatively. Our calculated masses are allowed to construct the Regge trajectories in both $(n_r, M^2)$ and $(J, M^2)$ planes. The mass spectra and the Regge trajectories study predict the spin-parity of $\Xi{_c(2970)^{+/0}}$, $\Xi{_c(3080)^{+/0}}$, $\Xi{_c(3123)^+}$, $\Omega{_c}(3000)^0$ and $\Omega{_c}(3119)^0$ baryons. Moreover, the strong one pion decay rates of the isodoublet states of $\Xi{_c(2645)}$, $\Xi{_c(2790)}$ and $\Xi{_c(2815)}$ are analyzed in the framework of Heavy Hadron Chiral Perturbation Theory (HHChPT). Also, the ground state magnetic moments and the radiative decay rates based on the transition magnetic moments are calculated in the framework of constituent quark model.

Halogen Bonding Facilitates Intersystem Crossing in Iodo-BODIPY Chromophores.

BODIPY chromophores can serve as organic-based triplet photosensitizers for a wide range of applications. To perform this function, the formation of the triplet state is critical, and a better understanding of how to modulate the formation of the triplet state could lead to further advances in BODIPY-based sensitizers for solar energy conversion and photodynamic therapy. In this work we investigate the ability of halogen bonding, a noncovalent solvent interaction, to facilitate intersystem crossing in a diiodo-BODIPY. Ultrafast transient absorption spectroscopy is applied to diiodo-BODIPY in the presence of pyridine-based halogen bonding solvent molecules to determine the rate constants for intersystem crossing. We find that halogen bonding facilitates the formation of the triplet state by increasing the intersystem crossing rate constant of diiodo-BODIPY. The results are interpreted in terms of the Marcus expression for intersystem crossing. Quantum chemical calculations show that halogen bonding acts to alter both the spin-orbit coupling terms and the relative energetics of the singlet and triplet states.

A Dispersive Optical Model Analysis of the Alpha Particles Scattering by Titanium Element Nucleus and Its Natural Isotopes

A dispersive optical model analysis of the alpha particles scattering by titanium element nucleus and its natural isotopes has been applied for a new scattering potential within the energy range (1-100) MeV which has contained the range of the Coulomb barrier, and for constant input values of the parameters of this potential. This potential is extent of the mean field potential and is called by (coulomb-nuclear) interference potential, that contains (spin-orbit) coulomb term. The results according to DOMACNIP program that has been designed for that purpose would contain: continuous energy variation of the depths of the real and imaginary parts of the mean field, which are connected by dispersion relations have been compared with these resulting from global parameterizations of the alpha particles scattering potential. In addition to continuous energy variation of the real radius parameter of the Wood-Saxon approximation to the mean field potential with its Hatree-Fock approximation of the nonlocal potential. Consequently, our results for the continuous energy variations of the predicted total reaction cross section within the energy range (1-100) MeV, and with calculation step of the pervious range whose magnitude (1 MeV), differential cross sections, Ratio of the differential elastic scattering cross section to Rutherford cross section and polarization resulted only from the Coulomb spin-orbit term that has been appeared characteristically for selected energy and for selected center-of-mass scattering angle within the energy range (1-100) MeV, showed the excellent agreement with available experimental data and better than these resulted from global parameterizations of the alpha particles scattering potential.

One-bond 1 J(15 N─19 F) spin-spin coupling constants of cationic fluorinating reagents: Insights from DFT calculations.

We have investigated, by means of density functional theory protocols, the one-bond 1 J(15 N─19 F) spin-spin coupling constants in a series of fluorinating reagents, containing the N─F bond, recently studied experimentally. The results of the calculations show a very good linear relationship with the experimental values, even though only the M06-2X(PCM)/pcJ-2//B3LYP/6-311G(d,p) level affords a very low mean absolute error. The calculations allow to analyze the various molecular orbitals contributions to the J coupling and to rationalize the observed positive sign, corresponding to a negative sign of the reduced spin-pin coupling constant K(N─F). Moreover, of the four Ramsey contributions, only the diamagnetic spin orbit is negligible, whereas the paramagnetic spin orbit and spin dipole terms decrease the magnitude of the Fermi contact (FC) term by an amount that goes from a minimum of 35% up to more than 60% of the FC term itself. Several effects have been investigated, namely, the contribution of the long-range solvent reaction field, relativistic corrections, and conformational and vibrational effects.

Linear response theory in asymmetric nuclear matter for Skyrme functionals including spin-orbit and tensor terms. II. Charge exchange

We present the formalism of linear response theory both at zero and finite temperature in the case of asymmetric nuclear matter excited by an isospin flip probe. The particle-hole interaction is derived from a general Skyrme functional that includes spin-orbit and tensor terms. Response functions are obtained by solving a closed algebraic system of equations. Spin strength functions are analyzed for typical values of density, momentum transfer, asymmetry and temperature.

Collective excitations involving spin and isospin degrees of freedom

In this paper, we discuss some new important developments in the study of isobaric analog states (IAS) and Gamow-Teller resonances (GTR). In the case of the IAS, we have shown the importance of taking into account charge symmetry breaking (CSB) and charge independence breaking (CIB) forces, in order to reconcile the reproduction of the IAS energy in 208Pb with the reproduction of some very basic observables like the neutron skin which, in turn, is strongly correlated with the density dependence of the symmetry energy. Isospin symmetry breaking terms can increase the energy of the IAS associated with Skyrme EDFs that produce a reasonable value of the neutron skin. In particular, this has been shown in the case of the SAMi functional. The GTR has a large damping width and its strength is experimentally found to be quenched with respect to standard RPA calculations. We have revised the PVC model for the width of giant resonances using the Skyrme force consistently for RPA (QRPA) and (quasi-)particle-vibration couplings (PVC or QPVC) calculations. We apply this model to the study of the GTR both in magic and open-shell nuclei. The results are in very good agreement with the experimental findings. The remaining discrepancies point to the necessity of fine tuning of the spin, spin-isospin, and spin-orbit terms in the existing EDFs. Some detailed formulas of CSB and CIB energy densities are given in the appendix.

Understanding the Role of Solvents and Spin-Orbit Coupling in an Oxygen-Assisted SN 2-Type Oxidative Transmetalation Reaction.

The aerial oxidation of PdII to PdIV has emerged as an integral component of sustainable catalytic C-H functionalization processes. However, a proper understanding of the factors that control the viability of this oxidative process remains elusive. An investigation of the intricate mechanism of the transmetalation reaction of the aerial oxidative transformation of [(Me3 tacn)PdII Me2 ] (Me3 tacn=N,N',N''-trimethyl-1,4,7-triazacyclononane) to [(Me3 tacn)PdIV Me3 ]+ has been conducted by using DFT, along with multireference methods, such as second-order n-electron valence-state perturbation theory (NEVPT2) with complete active space self-consistent field theory (CASSCF). The present endeavor predicts that the thermodynamics and kinetics of the oxygen activation step are primarily dictated by the polarity of the solvents, which determine the amount of charge transfer to the oxygen molecule from the PdII center. Additionally, it is observed that the presence of a protic solvent has a significant effect on the spin-orbit coupling term at the minimum energy crossing point of the triplet and singlet surfaces. Moreover, it is shown that the intermetal ligand-transfer phenomenon is an important instance of an oxygen-assisted SN 2 reaction.

Zeeman Tunability of Andreev Bound States in van der Waals Tunnel Barriers.

Quantum dots proximity coupled to superconductors are attractive research platforms due to the intricate interplay between the single-electron nature of the dot and the many body nature of the superconducting state. These have been studied mostly using nanowires and carbon nanotubes, which allow a combination of tunability and proximity. Here we report a new type of quantum dot which allows proximity to a broad range of superconducting systems. The dots are realized as embedded defects within semiconducting tunnel barriers in van der Waals layers. By placing such layers on top of thin NbSe_{2}, we can probe the Andreev bound state spectra of such dots up to high in-plane magnetic fields without observing the effects of a diminishing superconducting gap. As tunnel junctions defined on NbSe_{2} have a hard gap, we can map the subgap spectra without a background related to the rest of the junction. We find that the proximitized defect states invariably have a singlet ground state, manifest in the Zeeman splitting of the subgap excitation. We also find, in some cases, bound states that converge to zero energy and remain there. We discuss the role of the spin-orbit term, present both in the barrier and the superconductor, in the realization of such topologically trivial zero-energy states.

Energetics and structural properties of two- and three-boson systems in the presence of one-dimensional spin-orbit coupling

It was shown recently that the discrete scaling symmetry, which underlies the Efimov effect in the three identical boson system with two-body short-range interactions, survives when single-particle 1D spin-orbit coupling terms are added to the Hamiltonian. Each three-body energy level in the ordinary Efimov scenario turns into an energy manifold that contains four energy levels in the presence of 1D spin-orbit coupling (equal mixture of Rashba-Dresselhaus coupling). This work provides a detailed characterization of the energy levels in these manifolds. The two-boson energies, which enter into the three-boson scattering threshold, are analyzed in detail. Moreover, the structural properties, e.g., momentum distributions of the two- and three-boson systems, are analyzed for various parameter combinations.

Toward the evaluation of intersystem crossing rates with variational relativistic methods.

The change in electronic state from one spin multiplicity to another, known as intersystem crossing, occurs in molecules via the relativistic phenomenon of spin-orbit coupling. Current means of estimating intersystem crossing rates rely on the perturbative evaluation of spin-orbit coupling effects. This perturbative approach, valid in lighter atoms where spin-orbit coupling is weaker, is expected to break down for heavier elements where relativistic effects become dominant. Methods which incorporate spin-orbit effects variationally, such as the exact-two-component (X2C) method, will be necessary to treat this strong-coupling regime. We present a novel procedure which produces a diabatic basis of spin-pure electronic states coupled by spin-orbit terms, generated from fully variational relativistic calculations. This method is implemented within X2C using time-dependent density-functional theory and is compared to results from a perturbative relativistic study in the weak spin-orbit coupling regime. Additional calculations on a more strongly spin-orbit-coupled [UO2Cl4]2- complex further illustrate the strengths of this method. This procedure will be valuable in the estimation of intersystem crossing rates within strongly spin-coupled species.

Magnetism and optical properties of Yb3Al5O12 hosted Er3+ – experiment and theory

Using the recently developed method based on a combination of DFT plane wave code applied to extract the crystal field parameters and a local atomic like Hamiltonian involving electron-electron, spin-orbit and Zeeman terms we calculated the energy levels of ground and excited multiplets of Yb3+ and Er3+ ions hosted in ytterbium and yttrium aluminum garnet (YbAG and YAG) including their crystal and magnetic field splitting. The obtained energy levels and derived magnetic properties are compared with the experimental data from magnetometry, photoluminiscence and near-infrared spectroscopy.

Proton elastic scattering on calcium isotopes from chiral nuclear optical potentials

We formulate microscopic optical potentials for nucleon-nucleus scattering from chiral two- and three-nucleon forces. The real and imaginary central terms of the optical potentials are obtained from the nucleon self energy in infinite nuclear matter at a given density and isospin asymmetry, calculated self-consistently to second order in many-body perturbation theory. The real spin-orbit term is extracted from the same chiral potential using an improved density matrix expansion. The density-dependent optical potential is then folded with the nuclear density distributions of 40Ca, 42Ca, 44Ca, and 48Ca from which we study proton-nucleus elastic scattering and total reaction cross sections using the reaction code TALYS. We compare the results of the microscopic calculations to those of phenomenological models and experimental data up to projectile energies of E = 180 MeV. While overall satisfactory agreement with the available experimental data is obtained, we find that the elastic scattering and total reaction cross sections can be significantly improved with a weaker imaginary optical potential, particularly for larger projectile energies.

Density Functional Calculations of Electron Paramagnetic Resonance g- and Hyperfine-Coupling Tensors Using the Exact Two-Component (X2C) Transformation and Efficient Approximations to the Two-Electron Spin-Orbit Terms.

A two-component quasirelativistic density functional theory implementation of the computation of hyperfine and g-tensors at exact two-component (X2C) and Douglas-Kroll-Hess method (DKH) levels in the Turbomole code is reported and tested for a series of smaller 3d1, 4d1, and 5d1 complexes, as well as for some larger 5d7 Ir and Pt systems in comparison with earlier four-component matrix-Dirac-Kohn-Sham results. A main emphasis is placed on efficient approximations to the two-electron spin-orbit contributions, comparing an existing implementation of two variants of Boettger's "scaled nuclear spin-orbit" (SNSO) approximation in the code with a newly implemented atomic mean-field spin-orbit (AMFSO) approximation. The different variants perform overall comparably well with the four-component data. The AMFSO approximation has the added advantage of being able to include the spin-other-orbit contributions arising from the Gaunt term of relativistic electron-electron interactions. These are of comparably larger importance for the 3d complexes than for their heavier homologues. The excellent agreement between X2C and four-component electron paramagnetic resonance parameter results provides the opportunity to treat large systems efficiently and accurately with the computationally more expedient two-component quasirelativistic methodology.

Relativistic multimode pseudo-Jahn-Teller effect in planar molecules YX3 with D3h′ symmetry

• Relativistic multimode pseudo-Jahn-Teller effect 2 E ′ + 2 A 2 ″ × e ′ + a 2 ″ . • Planar tetratomic molecules Y X 3 with the odd number of electrons. • Double symmetry group D 3 h ′ . • Symmetry properties of electronic Hamiltonian. • Spin-orbit coupling terms. • Second order terms for electrostatic and spin-orbit contributions. • 6 × 6 vibronic matrix. • e ′ and a 2 ″ vibration normal modes. • 9 electrostatic and 10 spin-orbital real constant parameters. Relativistic multimode pseudo-Jahn-Teller effect 2 E ′ + 2 A 2 ″ × e ′ + a 2 ″ is considered for planar tetratomic molecules Y X 3 , which have the odd number of electrons and are characterized by the double symmetry group D 3 h ′ . Our analysis is based on the symmetry properties of electronic Hamiltonian, which includes spin-orbit coupling terms. Taylor series expansion of electronic Hamiltonian in terms of vibration normal modes e ′ and a 2 ″ is restricted by second order terms for electrostatic and spin-orbit contributions. The result of this research is 6 × 6 vibronic matrix, which depends on e ′ and a 2 ″ vibration normal modes and includes nine electrostatic and ten spin-orbital real constant parameters.

Influence of Scalar-Relativistic and Spin–Orbit Terms on the Plasmonic Properties of Pure and Silver-Doped Gold Chains

The unique plasmonic character of silver and gold nanoparticles has a wide range of applications, and tailoring this property by changing electronic and geometric structures has received a great de...

Pairing in nuclear matter and finite nuclei

Effects of pairing with isospin $T=0$ and $T=1$ are systematically studied in a model, which is based on a realistic nucleon-nucleon interaction and allows us to describe the transition from infinite nuclear matter to finite nuclei. Special attention is paid to the development of the spin-orbit term in the mean field of nucleons in finite nuclei. The spin-orbit term yields a drastic suppression of $T=0$ proton-neutron pairing but does not lead to a complete disappearance in finite nuclei. Arguments are presented as to why no clear evidence of $T=0$ pairing can be observed in the binding energies of finite nuclei.

Competing superconducting phases in the interacting two-dimensional electron gas with strong Rashba spin-orbit coupling

In this work we study interacting electrons on square lattice in the presence of strong Rashba spin-orbit interaction. The spin-orbit term forces the time-reversal electron states to be paired in even Cooper channels. For concreteness, we only consider the repulsive onsite Hubbard and nearest-neighbor coulomb interactions, the so called extended Hubbard model. To examine the superconducting instability we obtain the effective interaction between electrons within the random phase approximation and treat the pairing instabilities driven by charge and spin fluctuations and their combined effects. We mapped out the phase diagram of the model in terms of interactions and electron fillings, and found that while the $d_{xy}$ and $d_{x^2-y^2}$ symmetries are the most likely pairing symmetries driven by charge and spin fluctuations, respectively, the strong effect of both fluctuations yields higher angular momentum Cooper instability. The possibility of topological superconductivity and triplet pairing is also discussed.

Transport of a persistent spin helix drifting transverse to the spin texture

Time-resolved magneto-optic Kerr microscopy measures the effect of in-plane electric fields on the dynamics of a photoexcited spin distribution in a modulation-doped GaAs quantum well. The structure features nearly equal Dresselhaus and Rashba coefficients, such that there is negligible impact of spin-orbit coupling for electrons moving along the $[1\overline{1}0]$ or $[\overline{1}10]$ directions. Meanwhile, spin texture emerges for electrons moving in the $[110]$ or $[\overline{1}\overline{1}0]$ directions. The overall spin pattern resembles a persistent spin helix. An in-plane electric field, applied transverse to the spin texture (along the $[1\overline{1}0]$ or $[\overline{1}10]$ directions), introduces a drift of the spin packet and additional Larmor precessions, i.e., a marked decrease of the spatial periodicity of the spin pattern. The in-plane electric field also increases the temporal frequency of the evolving spin distribution, which is directly linked to the cubic Dresselhaus spin-orbit coupling term. Moreover, the in-plane field increases the diffusion coefficient by more than an order of magnitude. We attribute this effect to carrier heating and the separation of the photogenerated electron-hole dipole.

Out-of-plane magnetic anisotropy energy in the Ni3Bz3 molecule.

Organometallic complexes formed by transition metals clusters and benzene molecules have already been synthesized, and in selected cases display magnetic properties controlled by external magnetic fields. We have studied NinBzn complexes made of nickel atoms surrounded by benzene molecules and here we focus specifically on the magnetic molecule Ni3Bz3. By means of calculations including relativistic spin-orbit terms, we show that this molecule reveals a large magnetic anisotropy energy of approximately 8 meV, found with the easy axis perpendicular to the metal atom plane. Note that the matching bare Ni3 cluster has a similar magnetic anisotropy, however the easy axis is in-plane. Covering with benzene molecules thus switches the easy axis from in-plane for Ni3 to out-of-plane for Ni3Bz3. The large out-of-plane magnetic anisotropy of Ni3Bz3 suggests that this molecule could indeed be used as a part in the design of molecular magnetic memories.

Spin-orbit coupling effects in the quantum Hall regime probed by electron spin resonance

The spin resonance of two-dimensional (2D) electrons confined in a high-quality 4.5-nm AlAs quantum well was studied in the regime of the integer quantum Hall effect. The electron $g$-factor extracted from the magnetic field position of the spin resonance at a fixed microwave frequency demonstrated a strong nonlinear dependence on the magnetic field with discontinuities around even filling factors. The value of the $g$-factor tended to increase with a decrease of the magnetic field around each odd filling. Furthermore, the $g$-factor at the exactly odd filling factor $\ensuremath{\nu}$ turned out to be dependent on $\ensuremath{\nu}$, suggesting the entanglement between the spin degree of freedom and the orbital motion of the electrons in the regime of the integer quantum Hall effect. This suggestion is further supported, as all the experimental data are well described, when a Dresselhaus-type spin-orbit interaction is introduced into the Hamiltonian of a single electron in the quantizing magnetic field. Surprisingly, such excellent agreement was observed even in the case of tilted magnetic fields. The fitting procedure allowed us to determine the strength of the Dresselhaus spin-orbit term in a 2D electron system and to extract the fundamentally important Dresselhaus constant for bulk AlAs. Unexpectedly, not only was single spin resonance observed around even fillings, it tended to split into two well-resolved lines. Yet this finding remains a mystery and highlights the need for further experimental and theoretical efforts.