High-spin Systems Research Articles

Charged particle decay of hot and rotatingMo88nuclei in fusion-evaporation reactions

A study of fusion-evaporation and (partly) fusion-fission channels for the $^{88}$Mo compound nucleus, produced at different excitation energies in the reaction $^{48}$Ti + $^{40}$Ca at 300, 450 and 600 MeV beam energies, is presented. Fusion-evaporation and fusion-fission cross sections have been extracted and compared with the existing systematics. Experimental data concerning light charged particles have been compared with the prediction of the statistical model in its implementation in the Gemini++ code, well suited even for high spin systems, in order to tune the main model parameters in a mass region not abundantly covered by exclusive experimental data. Multiplicities for light charged particles emitted in fusion evaporation events are also presented. Some discrepancies with respect to the prediction of the statistical model have been found for forward emitted $\alpha$-particles; they may be due both to pre-equilibrium emission and to reaction channels (such as Deep Inelastic Collisions, QuasiFission/QuasiFusion) different from the compound nucleus formation.

Spin-nematic order in antiferromagnetic spinor condensates

Large spin systems can exhibit unconventional types of magnetic ordering different from the ferromagnetic or N\'eel-like antiferromagnetic order commonly found in spin 1/2 systems. Spin-nematic phases, for instance, do not break time-reversal invariance and their magnetic order parameter is characterized by a second rank tensor with the symmetry of an ellipsoid. Here we show direct experimental evidence for spin-nematic ordering in a spin-1 Bose-Einstein condensate of sodium atoms with antiferromagnetic interactions. In a mean field description this order is enforced by locking the relative phase between spin components. We reveal this mechanism by studying the spin noise after a spin rotation, which is shown to contain information hidden when looking only at averages. The method should be applicable to high spin systems in order to reveal complex magnetic phases.

Effective spin-chain model for strongly interacting one-dimensional atomic gases with an arbitrary spin

We present a general form of the effective spin-chain model for strongly interacting atomic gases with an arbitrary spin in one-dimensional (1D) traps. In particular, for high-spin systems the atoms can collide in multiple scattering channels, and we find that the resulting form of spin-chain model generically follows the same structure as that of the interaction potentials. This is a unified form working for any spin, statistics (Bose or Fermi), and confinement potentials. We adopt the spin-chain model to reveal both the ferromagnetic (FM) and antiferromagnetic (AFM) magnetic orders for strongly interacting spin-1 bosons in 1D traps. We further show that by adding the spin-orbit coupling, the FM and AFM orders can be gradually destroyed and eventually the ground state exhibits universal spin structure and contacts that are independent of the strength of spin-orbit coupling.

Qubit Control Limited by Spin-Lattice Relaxation in a Nuclear Spin-Free Iron(III) Complex.

High-spin transition metal complexes are of interest as candidates for quantum information processing owing to the tunability of the pairs of MS levels for use as quantum bits (qubits). Thus, the design of high-spin systems that afford qubits with stable superposition states is of primary importance. Nuclear spins are a potent instigator of superposition instability; thus, we probed the Ph4P(+) salt of the nuclear spin-free complex [Fe(C5O5)3](3-) (1) to see if long-lived superpositions were possible in such a system. Continuous-wave and pulsed electron paramagnetic resonance (EPR) spectroscopic measurements reveal a strong EPR transition at X-band that can be utilized as a qubit. However, at 5 K the coherent lifetime, T2, for this resonance is 721(3) ns and decreases rapidly with increasing temperature. Simultaneously, the spin-lattice relaxation time is extremely short, 11.33(1) μs, at 5 K, and also rapidly decreases with increasing temperature. The coincidence of these two temperature-dependent data sets suggests that T2 in 1 is strongly limited by the short T1. Importantly, these results highlight the need for new design parameters in pursuit of high-spin species with appreciable coherence times.

Effects of MnO doping on the electronic properties of zinc oxide: 406 GHz electron paramagnetic resonance spectroscopy and Newman superposition model analysis

MnO-doped ZnO ceramics have been synthesized through the conventional ceramic processing route. Mn2+ ions have been incorporated into the ZnO lattice within the limits of solid solubility. By using X-band-frequency and high-field electron paramagnetic resonance (EPR), we have resolved some of the main electronic transitions for the S = 5/2, I = 5/2 high-spin system and have determined accurately the EPR spin-Hamiltonian parameters. By combining data from crystallographic X-ray diffraction and EPR with the semi-empirical Newman superposition model, we have found the local configurational position of Mn2+ and have confirmed the symmetry of the lattice. The results presented in this contribution indicate that Mn ions substitute at Zn sites in ZnO. The effect of Mn2+ ions on the intrinsic defects becomes remarkable, thus the vacancy related intrinsic defect signals cannot be visible in the EPR spectrum. MnO doping affects the band gap energy of ZnO system which was confirmed via UV-Vis spectroscopy.

Dark State Adiabatic Passage with Branched Networks and High-Spin Systems: Spin Separation and Entanglement

Adiabatic methods are potentially important for quantum information protocols because of their robustness against many sources of technical and fundamental noise. They are particularly useful for quantum transport, and in some cases elementary quantum gates. Here we explore the extension of a particular protocol, dark state adiabatic passage, where a spin state is transported across a branched network of initialised spins, comprising one `input' spin, and multiple leaf spins. We find that maximal entanglement is generated in systems of spin-half particles, or where the system is limited to one excitation.

Vector magnetometry based onS=32electronic spins

Electronic spin systems with S>1/2 provide an efficient method for DC vector magnetometry, since the conventional electron spin resonance spectra at a given magnetic field reflect not only the field strength but also orientation in the presence of strong spin-spin interactions. S=1 spins, e.g. the nitrogen-vacancy centers in diamond, have been intensively investigated for such a purpose. In this report, we compare S=1 and S=3/2 spins, and discuss how one can apply general principles for the use of high spin systems as a vector magnetometer to the S=3/2 spin systems. We find analytical solutions which allow a reconstruction of the magnetic field strength and polar angle using the observed resonance transitions if an uniaxial symmetry exists for the spin-spin interaction as in S=1 systems. We also find that an ambiguity of determining the field parameters may arise due to the unique properties of S=3/2 systems, and present solutions for it utilizing additional transitions in the low-field region. The electronic spins of the silicon vacancy in silicon carbide will be introduced as a model for the S=3/2 DC vector magnetometer and the practical usage of it, including the magic-angle spinning type method, will be presented too.

Quantum correlations in Heisenberg XY spin-1 and spin-1/2 model with Dzyaloshinskii–Moriya interactions

We study the quantum correlations in a spin-1/2 (qubit) and spin-1 (qutrit) Heisenberg XY model separately, based on quantum discord (QD) and measurement-induced disturbance (MID) respectively. We find the evidence of the first- and second-order quantum phase transition (QPT) in both spin-1/2 and spin-1 systems. The effect of the temperature, magnetic field and Dzyaloshinskii–Moriya (DM) interactions on QPT and quantum correlation are also investigated. Finally, we observed that the QD and MID are not only vigorous for higher spin systems but also more robust than entanglement.

Propagation peculiarities of mean field massive gravity

Massive gravity (mGR) describes a dynamical “metric” on a fiducial, background one. We investigate fluctuations of the dynamics about mGR solutions, that is about its “mean field theory”. Analyzing mean field massive gravity (m‾GR) propagation characteristics is not only equivalent to studying those of the full non-linear theory, but also in direct correspondence with earlier analyses of charged higher spin systems, the oldest example being the charged, massive spin 3/2 Rarita–Schwinger (RS) theory. The fiducial and mGR mean field background metrics in the m‾GR model correspond to the RS Minkowski metric and external EM field. The common implications in both systems are that hyperbolicity holds only in a weak background-mean-field limit, immediately ruling both theories out as fundamental theories; a situation in stark contrast with general relativity (GR) which is at least a consistent classical theory. Moreover, even though both m‾GR and RS theories can still in principle be considered as predictive effective models in the weak regime, their lower helicities then exhibit superluminal behavior: lower helicity gravitons are superluminal as compared to photons propagating on either the fiducial or background metric. Thus our approach has uncovered a novel, dispersive, “crystal-like” phenomenon of differing helicities having differing propagation speeds. This applies both to m‾GR and mGR, and is a peculiar feature that is also problematic for consistent coupling to matter.

New unfolded higher spin systems in AdS3

We investigate the unfolded formulation of bosonic Lorentz tensor fields of arbitrary spin in containing a parity breaking mass parameter. They include deformations of the linearizations of the Prokushkin–Vasiliev higher spin theory around its critical points. They also provide unfolded formulations of linearized topologically massive higher spin fields including their critical versions. The gauge invariant degrees of freedom are captured by infinite towers of zero forms. We also introduce two inequivalent sets of gauge potentials given by trace constrained Fronsdal fields and trace unconstrained metric-like fields.

Simulation of multi-frequency EPR spectra for a distribution of the zero-field splitting

We present a numerical procedure called ‘grid-of-errors’ to extract the distribution of magnetic interactions from continuous-wave electron-paramagnetic-resonance (EPR) spectra at multiple microwave frequencies. The approach is based on the analysis of the lineshape of the spectra and explicitly worked out for high-spin systems for which the lineshape is determined by a distribution of the zero-field splitting. Initial principal values of the zero-field splitting tensor are obtained from the EPR spectrum at a microwave frequency in the high-field limit, and the initial distribution is taken Gaussian. Subsequently, the grid-of-errors procedure optimizes this distribution, without any restriction to its shape, taking into account spectra at various microwave frequencies. The numerical procedure is illustrated for the Fe(III)–EDTA complex. An optimized distribution of the zero-field splitting is obtained, which provides a proper description of the EPR spectra at 9.5, 34, 94, and 275GHz. The proposed approach can be used as well for distributions of magnetic interactions other than the zero-field splitting.

Coligand and solvent effects on the architectures and spin-crossover properties of (4,4)-connected Iron(II) coordination polymers.

The self-assemblies of 1,4-bis(pyrid-4-yl)benzene (bpb) and Fe(NCX)2 (X = S, Se, BH3) afforded six coordination polymers with the general formula of [Fe(bpb)2(NCX)2]·Y (X = S and Y = 3C2H5OH·2.5H2O for complex 4, X = S and Y = 2C2H5OH for 5, X = Se and Y = 2C2H5OH·H2O for 6, X = Se and Y = 0.67CH2Cl2·1.33C2H5OH·0.67H2O for 7, X = BH3 and Y = 3C2H5OH·2H2O for 8, X = BH3 and Y = 2CH2Cl2·2C2H5OH for 9). The frameworks of complexes 4 and 5 with the NCS(-) anion as coligand are supramolecular isomers, of which complex 4 features a threefold self-interpenetrated three-dimensional (3D) CdSO4-type topological structure with a Schläfli symbol of 6(5)·8, and complex 5 is a two-dimensional (2D) 4(4) rhombic grid network. These two complexes are purely high-spin systems. Complexes 6 and 7 with the NCSe(-) anion as coligand, both having the 3D 6(5)·8 CdSO4-type framework, show gradual and incomplete spin-crossover behaviors with transition temperature T1/2 being equal to 86 and 96 K, respectively. The usage of NCBH3(-) anion as coligand leads to the formation of 2D 4(4) rhombic grid networks for both complexes 8 and 9, which undergo relatively abrupt, complete spin crossover with T1/2 being equal to 247 and 189 K, respectively. The structural divergences are attributed to the coligands NCX(-) (X = S, Se, BH3) and solvent molecules. Meanwhile, a significant coligand effect is observed on the spin-crossover behaviors of these complexes, and the completeness and transition temperature of spin-state conversion depends on the nature of the coligand, that is, T1/2(NCS(-)) < T1/2(NCSe(-)) < T1/2(NCBH3(-)). These results further facilitate the design and synthesis of spin-crossover complexes with spin-state conversion.

Artificial magnetic fields in momentum space in spin-orbit-coupled systems

The Berry curvature is a geometrical property of an energy band which can act as a momentum-space magnetic field in the effective Hamiltonian of a wide range of systems. We apply the effective Hamiltonian to a spin-$\frac{1}{2}$ particle in two dimensions with spin-orbit coupling, a Zeeman field, and an additional harmonic trap. Depending on the parameter regime, we show how this system can be described in momentum space as either a Fock-Darwin Hamiltonian or a one-dimensional ring pierced by a magnetic flux. With this perspective, we interpret important single-particle properties, and identify analog magnetic phenomena in momentum space. Finally, we discuss the extension of this work to higher-spin systems, as well as experimental applications in ultracold atomic gases and photonic systems.

Third-Order Incremental Dual-Basis Set Zero-Buffer Approach for Large High-Spin Open-Shell Systems.

The third-order incremental dual-basis set zero-buffer approach (inc3-db-B0) is an efficient, accurate, and black-box quantum chemical method for obtaining correlation energies of large systems, and it has been successfully applied to many real chemical problems. In this work, we extend this approach to high-spin open-shell systems. In the open-shell approach, we will first decompose the occupied orbitals of a system into several domains by a K-means clustering algorithm. The essential part is that we preserve the active (singly occupied) orbitals in all the calculations of the domain correlation energies. The duplicated contributions of the active orbitals to the correlation energy are subtracted from the incremental expansion. All techniques of truncating the virtual space such as the B0 approximation can be applied. This open-shell inc3-db-B0 approach is combined with the CCSD and CCSD(T) methods and applied to the computations of a singlet-triplet gap and an electron detachment process. Our approach exhibits an accuracy better than 0.6 kcal/mol or 0.3 eV compared with the standard implementation, while it saves a large amount of the computational time and can be efficiently parallelized.

Emulating quantum state transfer through a spin-1 chain on a one-dimensional lattice of superconducting qutrits

Spin-1 systems, in comparison to spin-$\frac{1}{2}$ systems, offer a better security for encoding and transferring quantum information, primarily due to their larger Hilbert spaces. Superconducting artificial atoms possess multiple energy levels, thereby being capable of emulating higher-spin systems. Here I consider a one-dimensional lattice of nearest-neighbor-coupled superconducting transmon systems, and devise a scheme to transfer an arbitrary qutrit state (a state encoded in a three-level quantum system) across the chain. I assume adjustable couplings between adjacent transmons, derive an analytic constraint for the control pulse, and show how to satisfy the constraint to achieve a high-fidelity state transfer under current experimental conditions. My protocol thus enables enhanced quantum communication and information processing with promising superconducting qutrits.

Uniformizing higher-spin equations

Vasilievʼs higher-spin (HS) theories in various dimensions are uniformly represented as a simple system of equations. These equations and their gauge invariances are based on two superalgebras and have a transparent algebraic meaning. For a given HS theory these algebras can be inferred from the vacuum HS symmetries. The proposed system of equations admits a concise AKSZ formulation. We also discuss novel HS systems including partially-massless and massive fields in AdS, as well as conformal and massless off-shell fields.

Percolation features of cooperative Jahn-Teller systems: Ising EFT framework

Elastic exchange between two nearest Jahn-Teller (JT) centers in two or three dimensional dense crystals, can give an ordered macroscopic distortion known as cooperative JT effect (CJTE). A very diluted JT crystal does not show this effect. In the dynamic JT effect (DJTE), tunneling between different equivalent distorted wells has a pronounced influence on the CJTE. We investigate this phenomenon using a progressive increase in the concentration of these centers in the JT crystals, based on a bond percolation vector spin analogy technique within the framework of effective field theory (EFT). Mean field theory (MFT) was extensively used in previous studies of CJTE; however it neither includes correlation between JT centers in the lattice due to the complexity of the distortion field in the crystal nor the effect of tunneling between wells. We resort to an alternative procedure, by describing a JT center as a pseudo-spin vector $$\vec S$$ , induced to represent the degenerate JT-distorted states, where two nearest JT centers interact via an elastic exchange described by an Ising type spin interaction. The DJTE is considered to be similar to an elastic transverse field term in the Hamiltonian portraying the effect of tunneling between equivalent wells in the adiabatic potential energy surface (APES). We will be particularly discussing S = 1, S = 3/2 and S = 5/2 spin cases, where 2S + 1 wells in the APES are present and what JT systems they actually represent, with a percolative mechanism applied to the interactions between different JT centers. The different lattices are distinguished by their coordination numbers. Strong tunneling effects can suppress the CJTE and lead to a new state of criticality. Generalizations to higher spin systems will be obtained using a scaling technique. For the relevant distortions, we determine single site correlations, the macroscopic average distortion describing a structural phase transition and the elastic isothermal susceptibility as a function of temperature. The critical bond percolation threshold and the critical tunneling parameter are also obtained.

Entanglement and discord for qubits and higher spin systems

We discuss aspects of entanglement and quantum discord, two of the quantum correlations that are of much interest in the field of quantum information. Their definitions and handling will be discussed, with simple illustrative examples. A specific example is of entanglement decay resulting from a simple dissipative process and how to alter that decay. An analytical prescription for computing quantum discord when a qubit (spin-1/2 or two-level quantum system) is involved is presented along with applications, and its generalization to higher spins (many levels) indicated.

Collective mode evidence of high-spin bosonization in a trapped one-dimensional atomic Fermi gas with tunable spin

We calculate the frequency of collective modes of a one-dimensional repulsively interacting Fermi gas with high-spin symmetry confined in harmonic traps at zero temperature. This is a system realizable with fermionic alkaline-earth-metal atoms such as 173Yb, which displays an exact SU(κ) spin symmetry with κ⩾2 and behaves like a spinless interacting Bose gas in the limit of infinite spin components κ→∞, namely high-spin bosonization. We solve the homogeneous equation of state of the high-spin Fermi system by using Bethe ansatz technique and obtain the density distribution in harmonic traps based on local density approximation. The frequency of collective modes is calculated by exactly solving the zero-temperature hydrodynamic equation. In the limit of large number of spin-components, we show that the mode frequency of the system approaches that of a one-dimensional spinless interacting Bose gas, as a result of high-spin bosonization. Our prediction of collective modes is in excellent agreement with a very recent measurement for a Fermi gas of 173Yb atoms with tunable spin confined in a two-dimensional tight optical lattice.

Thermal Entanglement in the Spin-S Heisenberg XYZ Model

The thermal entanglement in the spin-S Heisenberg XYZ model is studied in detail by using the entanglement measure of negativity. The effects of spin on the thermal entanglement, the threshold temperature, the critical uniform external magnetic field, the nonuniform external magnetic field and the entanglement extremum are discussed, respectively. It is shown that with increasing spin, the entanglement will increase, and then decrease slowly. In addition, we find that entanglement will approach a constant Nc with the increase of DM interaction, the constant increases with the increase of spin, and both the threshold temperature Tc and critical uniform external magnetic field Bc will increase with the increasing spin. Thus high-spin system can inhibit the influence of the external environment better.