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Journal articles on the topic 'Complex spin systems'

Author: Grafiati

Published: 6 September 2023

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1

Mézard, Marc. "Spin glasses and optimization in complex systems." Europhysics News 53, no. 1 (2022): 15–17. http://dx.doi.org/10.1051/epn/2022105.

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Spin glasses are useless. Even the most imaginative physicists, submitted to grant pressure, could not find applications for these materials. Yet their study, triggered by pure intellectual interest, has created a formidable new branch of statistical physics distinguished this year by the Nobel prize attributed to Giorgio Parisi.

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2

Tareyeva, E. E., T. I. Schelkacheva, and N. M. Chtchelkatchev. "Spin-glass-type state in complex nonmagnetic systems." Theoretical and Mathematical Physics 160, no. 2 (August 2009): 1190–202. http://dx.doi.org/10.1007/s11232-009-0110-7.

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3

Andrianov, Timofey, and Anatoly Vedyayev. "Numerical simulation of spin transport in systems with complex geometry." EPJ Web of Conferences 185 (2018): 01021. http://dx.doi.org/10.1051/epjconf/201818501021.

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The spin diffusion and charge equations in Levy-Fert and Waintal models were numerically solved, using finite element method in complex non-collinear geometry with strongly inhomogeneous current flow. As an illustration, spin-dependent transport through a magnetic pillar and nonmagnetic spacer separating two magnetic layers was investigated. It is shown, that the structure with number of pillars gives a higher value of Giant Magnetoresistance (GMR) effect rather than a structure with one pillar of equivalent diameter. The inhomogeneity of spin currents, which has one of the strongest impacts on GMR effect value leads to the occurrence of spin-current vortices. Introduction of lT and lL lengths in Waintal model gives a better description of angular dependence of GMR effect rather than Levy-Fert model.

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4

Hammes-Schiffer, Sharon. "Quantum effects in complex systems: summarizing remarks." Faraday Discussions 221 (2020): 582–88. http://dx.doi.org/10.1039/c9fd00097f.

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Quantum mechanical phenomena such as coherence, spin dynamics, and tunneling have been observed in biological, electrochemical, polymeric, and many other condensed phase processes. This paper summarizes the diverse contributions to the Faraday Discussion on quantum effects in complex systems.

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5

Bora, Shuchi, H. C. Chandola, and B. S. Rajput. "Realizations of generators of complex angular momentum." Canadian Journal of Physics 68, no. 7-8 (July 1, 1990): 599–603. http://dx.doi.org/10.1139/p90-090.

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We use the generators of complex angular momentum in complex c3 space and derive the realizations of the homogeneous Lorentz group for nonzero real mass, zero mass, and imaginary mass systems. We use the appropriate little group for different systems to calculate the modifications in the spin contribution to angular momentum and the unphysical continuous spin representations are shown to be eliminated. We diagonalize the helicity operator in c3 space and obtain the generators of complex angular-momentum operators, which are shown to lead, in a general manner, to the standard helicity representations of the Poincare group for timelike and spacelike systems.

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6

Rüegge, Daniel, and Hanns Fischer. "Kinetic electron spin resonance spectroscopy of complex reaction systems." Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases 84, no. 10 (1988): 3187. http://dx.doi.org/10.1039/f19888403187.

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7

Borgs, C., J. T. Chayes, and J. Fröhlich. "Dobrushin states for classical spin systems with complex interactions." Journal of Statistical Physics 89, no. 5-6 (December 1997): 895–928. http://dx.doi.org/10.1007/bf02764213.

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8

Gibbon, J. D., and E. S. Titi. "Cluster formation in complex multi-scale systems." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 461, no. 2062 (August 12, 2005): 3089–97. http://dx.doi.org/10.1098/rspa.2005.1548.

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Based on the competition between members of a hierarchy of length scales in complex multi-scale systems, it is shown how clustering of active quantities into concentrated sets, like bubbles in a Swiss cheese, is a generic property that dominates the intermittent structure. The halo-like surfaces of these clusters have scaling exponents lower than that of their kernels, which can be as high as the domain dimension. Possible examples include spots in fluid turbulence and droplets in spin-glasses.

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9

Kapitan, Vitaliy Yu, Yuriy A. Shevchenko, Alexander V. Perzhu, and Egor V. Vasiliev. "Thermodynamic Properties of Heisenberg Spin Systems." Key Engineering Materials 806 (June 2019): 142–54. http://dx.doi.org/10.4028/www.scientific.net/kem.806.142.

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We present the simulation results of magnetic 2D and 3D structures with direct (for both of them) and Dzyaloshinskii-Moriya (DMI) (for 2D lattice) interactions in the frame of the Heisenberg model. We have adapted the multipath Metropolis algorithm for systems with complex types of exchange interactions and rough energy landscapes. We show the temperature behavior of magnetization, energy, and heat capacity, and reveal its critical temperatures and order parameter.

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10

IPATE, FLORENTIN, RALUCA LEFTICARU, and CRISTINA TUDOSE. "FORMAL VERIFICATION OF P SYSTEMS USING SPIN." International Journal of Foundations of Computer Science 22, no. 01 (January 2011): 133–42. http://dx.doi.org/10.1142/s0129054111007897.

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This paper presents an approach to P system verification using the Spin model checker. It proposes a P system implementation in PROMELA, the modeling language accepted by SPIN. It also provides the theoretical background for transforming the temporal logic properties expressed for the P system into properties of the executable implementation. Furthermore, a comparison between P systems verification using SPIN and NUSMV is realized. The results obtained show that the PROMELA implementation is more adequate, especially for verifying more complex models, such as P systems that model ecosystems.

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11

Cai, Jin-Yi, and Michael Kowalczyk. "Spin systems on k-regular graphs with complex edge functions." Theoretical Computer Science 461 (November 2012): 2–16. http://dx.doi.org/10.1016/j.tcs.2012.01.021.

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12

Hoffmann, Karl Heinz, and Paolo Sibani. "Relaxation and aging in spin glasses and other complex systems." Zeitschrift f�r Physik B Condensed Matter 80, no. 3 (October 1990): 429–38. http://dx.doi.org/10.1007/bf01323526.

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13

Tareyeva, E. E., T. I. Schelkacheva, and N. M. Chtchelkatchev. "ChemInform Abstract: Spin-Glass-Type State in Complex Nonmagnetic Systems." ChemInform 41, no. 36 (August 12, 2010): no. http://dx.doi.org/10.1002/chin.201036213.

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14

Kuz’min, V. S., and V. M. Kolesenko. "Coherent NMR responses in spin systems with complex spectral structure." Journal of Applied Spectroscopy 73, no. 3 (May 2006): 340–46. http://dx.doi.org/10.1007/s10812-006-0080-6.

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15

Timofeev, Ivan O., Olesya A. Krumkacheva, Matvey V. Fedin, Galina G. Karpova, and Elena G. Bagryanskaya. "Refining Spin–Spin Distance Distributions in Complex Biological Systems Using Multi-Gaussian Monte Carlo Analysis." Applied Magnetic Resonance 49, no. 3 (November 10, 2017): 265–76. http://dx.doi.org/10.1007/s00723-017-0965-y.

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16

Nikitina, M., and A. Bazhenov. "Phase Transitions in Ising Model Defined on Complex Networks." Reviews on Advanced Materials and Technologies 5, no. 1 (2023): 16–21. http://dx.doi.org/10.17586/2687-0568-2023-5-1-16-21.

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In this work, we consider an Ising model which allows spin-spin interaction in the systems. We assume that two-level quantum systems are randomly located in N nodes of a complex annealed scale-free network described by the Barabasi-Albert model. It is defined by the power-law degree distribution of nodes. We consider the mean-field approach to the system described by the Ising Hamiltonian. At a certain level, the system is totally characterized by the order parameter Sz. It contains a critical inverse temperature β, which depends on parameter ζ2 as the ratio of the second to the first moment of the degree distribution. We have found that for ζ2, that exceeds its critical value ζ2,c, high temperature phase transition occurs that can be explained by the hubs and clusters which appear in scale-free networks.

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17

Siddall, T. H., and R. L. Flurry. "Theory of nuclear magnetic resonance of higher-spin nuclei:A3B,A4B, and more complex spin-1 and spin-(3/2) systems." Physical Review B 31, no. 7 (April 1, 1985): 4153–60. http://dx.doi.org/10.1103/physrevb.31.4153.

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18

CONTUCCI, PIERLUIGI, CRISTIAN GIARDINÀ, CLAUDIO GIBERTI, and CECILIA VERNIA. "FINDING MINIMA IN COMPLEX LANDSCAPES: ANNEALED, GREEDY AND RELUCTANT ALGORITHMS." Mathematical Models and Methods in Applied Sciences 15, no. 09 (September 2005): 1349–69. http://dx.doi.org/10.1142/s0218202505000765.

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We consider optimization problems for complex systems in which the cost function has a multivalleyed landscape. We introduce a new class of dynamical algorithms which, using a suitable annealing procedure coupled with a balanced greedy-reluctant strategy drive the systems towards the deepest minimum of the cost function. Results are presented for the Sherrington–Kirkpatrick model of spin-glasses.

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19

Shill, Christopher R., and Joaquín E. Drut. "Particle Projection Using a Complex Langevin Method." EPJ Web of Conferences 175 (2018): 03003. http://dx.doi.org/10.1051/epjconf/201817503003.

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Using complex stochastic quantization, we implement a particle-number projection technique on the partition function of spin-1/2 fermions at finite temperature on the lattice. We discuss the method, its application towards obtaining the thermal properties of finite Fermi systems in three spatial dimensions, and results for the first five virial coefficients of one-dimensional, attractively interacting fermions.

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20

Campi, Gaetano, Nicola Poccia, Boby Joseph, Antonio Bianconi, Shrawan Mishra, James Lee, Sujoy Roy, et al. "Direct Visualization of Spatial Inhomogeneity of Spin Stripes Order in La1.72Sr0.28NiO4." Condensed Matter 4, no. 3 (August 10, 2019): 77. http://dx.doi.org/10.3390/condmat4030077.

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In several strongly correlated electron systems, the short range ordering of defects, charge and local lattice distortions are found to show complex inhomogeneous spatial distributions. There is growing evidence that such inhomogeneity plays a fundamental role in unique functionality of quantum complex materials. La1.72Sr0.28NiO4 is a prototypical strongly correlated perovskite showing spin stripes order. In this work we present the spatial distribution of the spin order inhomogeneity by applying micro X-ray diffraction to La1.72Sr0.28NiO4, mapping the spin-density-wave order below the 120 K onset temperature. We find that the spin-density-wave order shows the formation of nanoscale puddles with large spatial fluctuations. The nano-puddle density changes on the microscopic scale forming a multiscale phase separation extending from nanoscale to micron scale with scale-free distribution. Indeed spin-density-wave striped puddles are disconnected by spatial regions with negligible spin-density-wave order. The present work highlights the complex spatial nanoscale phase separation of spin stripes in nickelate perovskites and opens new perspectives of local spin order control by strain.

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21

Xu, Jingyan, Dmitry Budker, and Danila A. Barskiy. "Visualization of dynamics in coupled multi-spin systems." Magnetic Resonance 3, no. 2 (August 9, 2022): 145–60. http://dx.doi.org/10.5194/mr-3-145-2022.

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Abstract. Since the dawn of quantum mechanics, ways to visualize spins and their interactions have attracted the attention of researchers and philosophers of science. In this work we present a generalized measurement-based 3D-visualization approach for describing dynamics in strongly coupled spin ensembles. The approach brings together angular momentum probability surfaces (AMPS), Husimi Q functions, and DROPS (discrete representations of operators for spin systems) and finds particular utility when the total angular momentum basis is used for describing Hamiltonians. We show that, depending on the choice of a generalized measurement operator, the plotted surfaces either represent probabilities of finding the maximal projection of an angular momentum along any direction in space or represent measurable coherences between the states with different total angular momenta. Such effects are difficult to grasp by looking at (time-dependent) numerical values of density-matrix elements. The approach is complete in a sense that there is one-to-one correspondence between the plotted surfaces and the density matrix. Three examples of nuclear spin dynamics in two-spin systems are visualized: (i) a zero- to ultralow-field (ZULF) nuclear magnetic resonance (NMR) experiment in the presence of a magnetic field applied perpendicularly to the sensitive axis of the detector, (ii) interplay between chemical exchange and spin dynamics during high-field signal amplification by reversible exchange (SABRE), and (iii) a high-field spin-lock-induced crossing (SLIC) sequence, with the initial state being the singlet state between two spins. The presented visualization technique facilitates intuitive understanding of spin dynamics during complex experiments as exemplified here by the considered cases. Temporal sequences (“the movies”) of such surfaces show phenomena like interconversion of spin order between the coupled spins and are particularly relevant in ZULF NMR.

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22

Bushuev, Mark B., Denis P. Pishchur, Elena B. Nikolaenkova, and Viktor P. Krivopalov. "Compensation effects and relation between the activation energy of spin transition and the hysteresis loop width for an iron(ii) complex." Physical Chemistry Chemical Physics 18, no. 25 (2016): 16690–99. http://dx.doi.org/10.1039/c6cp01892k.

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Wide thermal hysteresis loops for iron(ii) spin crossover complexes are associated with high activation barriers: the higher the activation barrier, the wider the hysteresis loop for a series of related spin crossover systems.

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23

Chern, Gia-Wei. "Novel Magnetic Orders and Ice Phases in Frustrated Kondo-Lattice Models." SPIN 05, no. 02 (June 2015): 1540006. http://dx.doi.org/10.1142/s2010324715400068.

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We review recent theoretical progress in our understanding of electron-driven novel magnetic phases on frustrated lattices. Our specific focus is on Kondo-lattice or double-exchange models assuming finite magnetic moments localized at the lattice sites. A salient feature of systems with SU(2) symmetric local moments is the emergence of noncoplanar magnetic ordering driven by the conduction electrons. The complex spin textures then endow the electrons a nontrivial Berry phase, often giving rise to a topologically nontrivial electronic state. The second part of the review is devoted to the discussion of metallic spin ice systems, which are essentially frustrated Ising magnets with local spin ordering governed by the so-called ice rules. These rules are similar to those that describe proton configurations in solid water ice, hence the name "spin ice". The nontrivial spin correlations in the ice phase give rise to unusual electron transport properties in metallic spin-ice systems.

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24

von Korff Schmising, Clemens, Felix Willems, Sangeeta Sharma, Kelvin Yao, Martin Borchert, Martin Hennecke, Daniel Schick, et al. "Element-Specific Magnetization Dynamics of Complex Magnetic Systems Probed by Ultrafast Magneto-Optical Spectroscopy." Applied Sciences 10, no. 21 (October 28, 2020): 7580. http://dx.doi.org/10.3390/app10217580.

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The vision to manipulate and control magnetism with light is driven on the one hand by fundamental questions of direct and indirect photon-spin interactions, and on the other hand by the necessity to cope with ever growing data volumes, requiring radically new approaches on how to write, read and process information. Here, we present two complementary experimental geometries to access the element-specific magnetization dynamics of complex magnetic systems via ultrafast magneto-optical spectroscopy in the extreme ultraviolet spectral range. First, we employ linearly polarized radiation of a free electron laser facility to demonstrate decoupled dynamics of the two sublattices of an FeGd alloy, a prerequisite for all-optical magnetization switching. Second, we use circularly polarized radiation generated in a laboratory-based high harmonic generation setup to show optical inter-site spin transfer in a CoPt alloy, a mechanism which only very recently has been predicted to mediate ultrafast metamagnetic phase transitions.

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25

Aguilar, Juan A., Mathias Nilsson, and Gareth A. Morris. "Simple Proton Spectra from Complex Spin Systems: Pure Shift NMR Spectroscopy Using BIRD." Angewandte Chemie International Edition 50, no. 41 (August 31, 2011): 9716–17. http://dx.doi.org/10.1002/anie.201103789.

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Aguilar, Juan A., Mathias Nilsson, and Gareth A. Morris. "Simple Proton Spectra from Complex Spin Systems: Pure Shift NMR Spectroscopy Using BIRD." Angewandte Chemie 123, no. 41 (August 31, 2011): 9890–91. http://dx.doi.org/10.1002/ange.201103789.

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27

Samarakoon, Anjana, Taku J. Sato, Tianran Chen, Gai-Wei Chern, Junjie Yang, Israel Klich, Ryan Sinclair, Haidong Zhou, and Seung-Hun Lee. "Aging, memory, and nonhierarchical energy landscape of spin jam." Proceedings of the National Academy of Sciences 113, no. 42 (October 3, 2016): 11806–10. http://dx.doi.org/10.1073/pnas.1608057113.

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The notion of complex energy landscape underpins the intriguing dynamical behaviors in many complex systems ranging from polymers, to brain activity, to social networks and glass transitions. The spin glass state found in dilute magnetic alloys has been an exceptionally convenient laboratory frame for studying complex dynamics resulting from a hierarchical energy landscape with rugged funnels. Here, we show, by a bulk susceptibility and Monte Carlo simulation study, that densely populated frustrated magnets in a spin jam state exhibit much weaker memory effects than spin glasses, and the characteristic properties can be reproduced by a nonhierarchical landscape with a wide and nearly flat but rough bottom. Our results illustrate that the memory effects can be used to probe different slow dynamics of glassy materials, hence opening a window to explore their distinct energy landscapes.

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Fring, Andreas. "PT -symmetric deformations of integrable models." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 1989 (April 28, 2013): 20120046. http://dx.doi.org/10.1098/rsta.2012.0046.

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We review recent results on new physical models constructed as -symmetrical deformations or extensions of different types of integrable models. We present non-Hermitian versions of quantum spin chains, multi-particle systems of Calogero–Moser–Sutherland type and nonlinear integrable field equations of Korteweg–de Vries type. The quantum spin chain discussed is related to the first example in the series of the non-unitary models of minimal conformal field theories. For the Calogero–Moser–Sutherland models, we provide three alternative deformations: a complex extension for models related to all types of Coxeter/Weyl groups; models describing the evolution of poles in constrained real-valued field equations of nonlinear integrable systems; and genuine deformations based on antilinearly invariant deformed root systems. Deformations of complex nonlinear integrable field equations of Korteweg–de Vries type are studied with regard to different kinds of -symmetrical scenarios. A reduction to simple complex quantum mechanical models currently under discussion is presented.

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29

Borasi, Luigi. "Finite dimensional systems of free fermions and diffusion processes on spin groups." Journal of Mathematical Physics 63, no. 3 (March 1, 2022): 032102. http://dx.doi.org/10.1063/5.0063424.

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In this article, we are concerned with “finite dimensional fermions,” by which we mean vectors in a finite dimensional complex space embedded in the exterior algebra over itself. These fermions are spinless but possess the characterizing anticommutativity property. We associate invariant complex vector fields on the Lie group Spin(2 n + 1) to the fermionic creation and annihilation operators. These vector fields are elements of the complexification of the regular representation of the Lie algebra [Formula: see text]. As such, they do not satisfy the canonical anticommutation relations; however, once they have been projected onto an appropriate subspace of L2(Spin(2 n + 1)), these relations are satisfied. We define a free time evolution of this system of fermions in terms of a symmetric positive-definite quadratic form in the creation–annihilation operators. The realization of fermionic creation and annihilation operators brought by the (invariant) vector fields allows us to interpret this time evolution in terms of a positive self-adjoint operator that is the sum of a second order operator, which generates a stochastic diffusion process, and a first order complex operator, which strongly commutes with the second order operator. A probabilistic interpretation is given in terms of a Feynman–Kac-like formula with respect to the diffusion process associated with the second order operator.

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WANG, CHUN-YANG, WEN-XIAN YANG, and HONG DU. "SUPERIORITY OF GENERALIZED BOND-MOVING RENORMALIZATION IN STUDYING PHASE TRANSITION OF COMPLEX SPIN SYSTEMS." International Journal of Modern Physics B 27, no. 32 (December 2013): 1350187. http://dx.doi.org/10.1142/s0217979213501877.

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The superiority of the generalized Migdal–Kadanoff bond-moving renormalization (GMKBR) method in studying phase transition of complex spin systems is revealed by a sampled application on the classical S4 model. In three different cases of nearest-neighbor, next-nearest neighbor and external field, we obtain the critical points and further calculate the critical exponents according to the scaling theory. In all the cases, it is shown that the method is of great convenience in obtaining results which are in good conformity with the previous ones.

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Şaka, İrfan, Sedat Gümüş, and Azmi Gençten. "A Complete Product Operator Theory for IS (I=1, S = 1) Spin System and Application to 3D HMQC-COSY NMR Experiment." Zeitschrift für Naturforschung A 64, no. 5-6 (June 1, 2009): 377–86. http://dx.doi.org/10.1515/zna-2009-5-612.

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There exist a variety of multi-pulse NMR experiments for spectral assignment of complex molecules in solution. The conventional heteronuclear multiple-quantum coherence (HMQC) NMR experiment provides correlation between weakly coupled hetero-nuclei. The COSY is one of the most popular two-dimensional NMR experiment which is used to correlate J-coupled homo-nuclei of spectral assignment. The combination of the conventional HMQC and COSY NMR experiments yields a new experiment called 3D HMQC-COSY NMR experiment. The product operator theory is widely used for the analytical descriptions of multi-pulse NMR experiments for weakly coupled spin systems in liquids. In this study, complete product operator theory for weakly coupled IS (I = 1, S = 1) spin system is presented by obtaining the evolutions of the product operators under the spin-spin coupling Hamiltonian. As an application and a verification, analytical descriptions of 3D HMQC-COSY NMR experiment are obtained for weakly coupled ISnI’_S’m (I = I’ = 1/2; S = S’ = 1; n = 1,2, 3; m = 1, 2) multi-spin systems. Then the estimated spectra of this experiment for various multi-spin systems are explained in detail.

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Ibrahim, Yahaya. "Lattice connectivity and entanglement in quantum spin-glasses." UMYU Scientifica 1, no. 1 (September 30, 2022): 332–35. http://dx.doi.org/10.56919/usci.1122.042.

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I have studied the role of lattice connectivity and coupling weights distribution on the entanglement of quantum spin-glasses. It's found in this work that the connectivity of the lattice weakly influence the degree of entanglement in the spin-glass compared to the distribution of the coupling constants between the spins. This suggest important implications for machine learning models such as Boltzmann machines and the study of complex quantum systems.

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Pei, Michael Y., and Stephen R. Clark. "Neural-Network Quantum States for Spin-1 Systems: Spin-Basis and Parameterization Effects on Compactness of Representations." Entropy 23, no. 7 (July 9, 2021): 879. http://dx.doi.org/10.3390/e23070879.

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Neural network quantum states (NQS) have been widely applied to spin-1/2 systems, where they have proven to be highly effective. The application to systems with larger on-site dimension, such as spin-1 or bosonic systems, has been explored less and predominantly using spin-1/2 Restricted Boltzmann Machines (RBMs) with a one-hot/unary encoding. Here, we propose a more direct generalization of RBMs for spin-1 that retains the key properties of the standard spin-1/2 RBM, specifically trivial product states representations, labeling freedom for the visible variables and gauge equivalence to the tensor network formulation. To test this new approach, we present variational Monte Carlo (VMC) calculations for the spin-1 anti-ferromagnetic Heisenberg (AFH) model and benchmark it against the one-hot/unary encoded RBM demonstrating that it achieves the same accuracy with substantially fewer variational parameters. Furthermore, we investigate how the hidden unit complexity of NQS depend on the local single-spin basis used. Exploiting the tensor network version of our RBM we construct an analytic NQS representation of the Affleck-Kennedy-Lieb-Tasaki (AKLT) state in the xyz spin-1 basis using only M=2N hidden units, compared to M∼O(N2) required in the Sz basis. Additional VMC calculations provide strong evidence that the AKLT state in fact possesses an exact compact NQS representation in the xyz basis with only M=N hidden units. These insights help to further unravel how to most effectively adapt the NQS framework for more complex quantum systems.

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Sone, N., and P. Nicholls. "Complexes of cytochrome caa3 from the thermophilic bacterium PS3 formed with ligands and during catalytic activity." Canadian Journal of Biochemistry and Cell Biology 63, no. 3 (March 1, 1985): 153–61. http://dx.doi.org/10.1139/o85-022.

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PS3 (thermophilic bacterium) cytochrome caa3 reacts slowly with cyanide which forms a low-spin complex with the CuBa3 centre. Partial reduction under catalytic conditions increases the rate of cyanide binding, and the reaction constant is rather similar to that of the mammalian enzyme, but the partially reduced complex dissociates more rapidly than does the corresponding eukaryotic complex. A simple biphasic reaction can account for the results obtained. The azide complex of partially reduced PS3 cytochrome caa3 shows an α-peak blue shift similar to that of the mammalian enzyme. PS3 cytochrome caa3, forms an oxyferri ("oxygenated") species like the mammalian enzyme, but does not undergo high- to low-spin changes during the aerobic steady state with ascorbate and N,N,N′,N′-tetramethyl-p-phenylenediamine as substrates. Interactions seen in cytochrome oxidase – ligand reactions and its spin-state changes are therefore intrinsic to the enzyme's large catalytic subunits and do not require the presence of the small nuclear-encoded subunits found in eukaryotic systems.

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Zivieri, Roberto, and Giancarlo Consolo. "Hamiltonian and Lagrangian Dynamical Matrix Approaches Applied to Magnetic Nanostructures." Advances in Condensed Matter Physics 2012 (2012): 1–16. http://dx.doi.org/10.1155/2012/765709.

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Two micromagnetic tools to study the spin dynamics are reviewed. Both approaches are based upon the so-called dynamical matrix method, a hybrid micromagnetic framework used to investigate the spin-wave normal modes of confined magnetic systems. The approach which was formulated first is the Hamiltonian-based dynamical matrix method. This method, used to investigate dynamic magnetic properties of conservative systems, was originally developed for studying spin excitations in isolated magnetic nanoparticles and it has been recently generalized to study the dynamics of periodic magnetic nanoparticles. The other one, the Lagrangian-based dynamical matrix method, was formulated as an extension of the previous one in order to include also dissipative effects. Such dissipative phenomena are associated not only to intrinsic but also to extrinsic damping caused by injection of a spin current in the form of spin-transfer torque. This method is very accurate in identifying spin modes that become unstable under the action of a spin current. The analytical development of the system of the linearized equations of motion leads to a complex generalized Hermitian eigenvalue problem in the Hamiltonian dynamical matrix method and to a non-Hermitian one in the Lagrangian approach. In both cases, such systems have to be solved numerically.

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36

Allami, Ahmed J., Maria Grazia Concilio, Pavan Lally, and Ilya Kuprov. "Quantum mechanical MRI simulations: Solving the matrix dimension problem." Science Advances 5, no. 7 (July 2019): eaaw8962. http://dx.doi.org/10.1126/sciadv.aaw8962.

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We propose a solution to the matrix dimension problem in quantum mechanical simulations of MRI (magnetic resonance imaging) experiments on complex molecules. This problem is very old; it arises when Kronecker products of spin operators and spatial dynamics generators are taken—the resulting matrices are far too large for any current or future computer. However, spin and spatial operators individually have manageable dimensions, and we note here that the action by their Kronecker products on any vector may be computed without opening those products. This eliminates large matrices from the simulation process. MRI simulations for coupled spin systems of complex metabolites in three dimensions with diffusion, flow, chemical kinetics, and quantum mechanical treatment of spin relaxation are now possible. The methods described in this paper are implemented in versions 2.4 and later of the Spinach library.

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37

Delcey, Mickaël G., Rebecka Lindblad, Martin Timm, Christine Bülow, Vicente Zamudio-Bayer, Bernd von Issendorff, J. Tobias Lau, and Marcus Lundberg. "Soft X-ray signatures of cationic manganese–oxo systems, including a high-spin manganese(v) complex." Physical Chemistry Chemical Physics 24, no. 6 (2022): 3598–610. http://dx.doi.org/10.1039/d1cp03667j.

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Limitations in synthesis of high-valent metal–oxo complexes are circumvented by trapping a series of ionic Mn–oxo complexes. One of them is a rare high-spin Mn(v)–oxo, which can serve as a template to identify similar intermediates in catalysis.

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38

CALABRESE, PASQUALE, ANDREA PELISSETTO, PAOLO ROSSI, and ETTORE VICARI. "FIELD THEORY RESULTS FOR THREE-DIMENSIONAL TRANSITIONS WITH COMPLEX SYMMETRIES." International Journal of Modern Physics B 17, no. 31n32 (December 30, 2003): 5829–38. http://dx.doi.org/10.1142/s0217979203023355.

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We discuss several examples of three-dimensional critical phenomena that can be described by Landau–Ginzburg–Wilson ϕ4 theories. We present an overview of field-theoretical results obtained from the analysis of high-order perturbative series in the frameworks of the ∊ and of the fixed-dimension d=3 expansions. In particular, we discuss the stability of the O (N)-symmetric fixed point in a generic N-component theory, the critical behaviors of randomly dilute Ising-like systems and frustrated spin systems with noncollinear order, and the multicritical behavior arising from the competition of two distinct types of ordering with symmetry O (n1) and O (n2) respectively.

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39

Burton, J. D., and E. Y. Tsymbal. "Magnetoelectric interfaces and spin transport." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, no. 1977 (October 28, 2012): 4840–55. http://dx.doi.org/10.1098/rsta.2012.0205.

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Engineered heterostructures designed for electric control of magnetic properties, the so-called magnetoelectric interfaces , present a novel route towards using the spin degree of freedom in electronic devices. Here, we review how a subset of such interfaces, namely ferromagnet–ferroelectric heterostructures, display electronically mediated control of magnetism and, in particular, emphasis is placed on how these effects manifest themselves as detectable spin-dependent transport phenomena. Examples of these effects are given for a variety of material systems on the basis of ferroelectric oxides, manganese and ruthenium magnetic complex oxides and elemental ferromagnetic metals. Results from both theory and experiment are discussed.

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40

Furman, G. B., S. D. Goren, V. M. Meerovich, and V. L. Sokolovsky. "Fictitious spin-12 operators and correlations in quadrupole nuclear spin system." International Journal of Quantum Information 16, no. 01 (February 2018): 1850008. http://dx.doi.org/10.1142/s0219749918500089.

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The Hamiltonian and the spin operators for a spin 3/2 are represented in the basis formed by the Kronecker productions of the [Formula: see text] Pauli matrices. This reformulation allows us to represent a spin 3/2 as a system of two coupled fictitious spins 1/2. Correlations between these fictitious spins are studied using well-developed methods. We investigate the temperature and field dependences of correlations, such as mutual information, classical correlations, entanglement, and geometric and quantum discords in the fictitious spin-1/2 system describing a nuclear spin 3/2 which is placed in magnetic and inhomogeneous electric fields. It is shown that the correlations between the fictitious spins demonstrate properties which differ from those of real two-spin systems. In contrast to real systems all the correlations between the fictitious spins do not vanish with increasing external magnetic field; at a high magnetic field the correlations tend to their limiting values. Classical correlations, quantum and geometric discords reveal a pronounced asymmetry relative to the measurements on subsystems (fictitious spins) even in a uniform magnetic field and at symmetrical EFG, [Formula: see text]. The correlations depend also on the distribution of external charges, on the parameter of symmetry [Formula: see text]. At [Formula: see text] quantum and geometric discords have finite values in a zero magnetic field. The proposed approach may be useful in analysis of properties of particles with larger angular momentum, can provide the way to discover new physical phenomenon of quantum correlations, and can be a useful tool for similar definitions of other physical quantities of complex systems.

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41

Kitakawa, Colin, Tomohiro Maruyama, Jinta Oonari, Yuki Mitsuta, Takashi Kawakami, Mitsutaka Okumura, Kizashi Yamaguchi, and Shusuke Yamanaka. "Linear Response Functions of Densities and Spin Densities for Systematic Modeling of the QM/MM Approach for Mono- and Poly-Nuclear Transition Metal Systems." Molecules 24, no. 4 (February 25, 2019): 821. http://dx.doi.org/10.3390/molecules24040821.

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We applied our analysis, based on a linear response function of density and spin density, to two typical transition metal complex systems-the reaction centers of P450, and oxygen evolving center in Photosystem II, both of which contain open-shell transition metal ions. We discuss the relationship between LRF of electron density and spin density and the types of units and interactions of the systems. The computational results are discussed in relation to quantum mechanics (QM) cluster and quantum mechanics/molecular mechanics (QM/MM) modeling that are employed to compute the reaction centers of enzymes.

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42

Köhler, C., G. Seifert, U. Gerstmann, M. Elstner, H. Overhof, and Th Frauenheim. "Approximate density-functional calculations of spin densities in large molecular systems and complex solids." Physical Chemistry Chemical Physics 3, no. 23 (September 21, 2001): 5109–14. http://dx.doi.org/10.1039/b105782k.

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43

THURNER, STEFAN, and RUDOLF HANEL. "THE ENTROPY OF NON-ERGODIC COMPLEX SYSTEMS — A DERIVATION FROM FIRST PRINCIPLES." International Journal of Modern Physics: Conference Series 16 (January 2012): 105–15. http://dx.doi.org/10.1142/s2010194512007817.

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In information theory the 4 Shannon-Khinchin1,2 (SK) axioms determine Boltzmann Gibbs entropy, S ~ -∑i pi log pi, as the unique entropy. Physics is different from information in the sense that physical systems can be non-ergodic or non-Markovian. To characterize such strongly interacting, statistical systems – complex systems in particular – within a thermodynamical framework it might be necessary to introduce generalized entropies. A series of such entropies have been proposed in the past decades. Until now the understanding of their fundamental origin and their deeper relations to complex systems remains unclear. To clarify the situation we note that non-ergodicity explicitly violates the fourth SK axiom. We show that by relaxing this axiom the entropy generalizes to, S ~∑i Γ(d + 1, 1 - c log pi), where Γ is the incomplete Gamma function, and c and d are scaling exponents. All recently proposed entropies compatible with the first 3 SK axioms appear to be special cases. We prove that each statistical system is uniquely characterized by the pair of the two scaling exponents (c, d), which defines equivalence classes for all systems. The corresponding distribution functions are special forms of Lambert-W exponentials containing, as special cases, Boltzmann, stretched exponential and Tsallis distributions (power-laws) – all widely abundant in nature. This derivation is the first ab initio justification for generalized entropies. We next show how the phasespace volume of a system is related to its generalized entropy, and provide a concise criterion when it is not of Boltzmann-Gibbs type but assumes a generalized form. We show that generalized entropies only become relevant when the dynamically (statistically) relevant fraction of degrees of freedom in a system vanishes in the thermodynamic limit. These are systems where the bulk of the degrees of freedom is frozen. Systems governed by generalized entropies are therefore systems whose phasespace volume effectively collapses to a lower-dimensional 'surface'. We explicitly illustrate the situation for accelerating random walks, and a spin system on a constant-conectancy network. We argue that generalized entropies should be relevant for self-organized critical systems such as sand piles, for spin systems which form meta-structures such as vortices, domains, instantons, etc., and for problems associated with anomalous diffusion.

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Vlaovič, Boštjan, and Aleksander Vreže. "Discrete Time Model for Process Meta Language with Fictitious-Clock." Applied Sciences 12, no. 6 (March 15, 2022): 2990. http://dx.doi.org/10.3390/app12062990.

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Industries like telecommunications, medical, automotive, military, avionics, and aerospace use complex real-time systems. Specification and Description Language (SDL) is one of the leading domain specific languages that is formally defined by international standards and well established in describing such systems. To check system properties abstracted model of the system is prepared in selected modeling language. We use Spin (Simple Promela Interpreter) model checker that is one of the leading tools for verification of complex concurrent and reactive systems. This paper focuses on modeling the SDL timer construct. It is one of the SDL constructs that is not easily modeled with Promela, but is present in many SDL systems. After an overview of the related work we propose a new Discrete Time Model for Promela (DTMP) that is seamlessly integrated in our framework for modeling SDL systems and can be used with the mainstream version of the Spin tool. To the best of our knowledge, this is not possible with the existing solutions. We describe how DTMP can be used to model SDL systems that use timers. Experimental results demonstrate its applicability to non-SDL systems with Fischer’s mutual exclusion protocol and the Parallel Acknowledgment with Retransmission that were used in prior studies. We compare state-space requirements with one of the existing solutions DT Promela and DT Spin. With that, virtues and shortcomings of this high-level solution are exposed. We have shown that DTMP is effective when an extensive range of timer expiration values are used, which is usually the case in real-life SDL systems.

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Anderson, Justin Q., P. A. Praveen Janantha, Diego A. Alcala, Mingzhong Wu, and Lincoln D. Carr. "Physical realization of complex dynamical pattern formation in magnetic active feedback rings." New Journal of Physics 24, no. 3 (March 1, 2022): 033018. http://dx.doi.org/10.1088/1367-2630/ac47cb.

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Abstract We report the clean experimental realization of cubic–quintic complex Ginzburg–Landau (CQCGL) physics in a single driven, damped system. Four numerically predicted categories of complex dynamical behavior and pattern formation are identified for bright and dark solitary waves propagating around an active magnetic thin film-based feedback ring: (1) periodic breathing; (2) complex recurrence; (3) spontaneous spatial shifting; and (4) intermittency. These nontransient, long lifetime behaviors are observed in self-generated spin wave envelopes circulating within a dispersive, nonlinear yttrium iron garnet waveguide. The waveguide is operated in a ring geometry in which the net losses are directly compensated for via linear amplification on each round trip (of the order of 100 ns). These behaviors exhibit periods ranging from tens to thousands of round trip times (of the order of μs) and are stable for 1000s of periods (of the order of ms). We present ten observations of these dynamical behaviors which span the experimentally accessible ranges of attractive cubic nonlinearity, dispersion, and external field strength that support the self-generation of backward volume spin waves in a four-wave-mixing dominant regime. Three-wave splitting is not explicitly forbidden and is treated as an additional source of nonlinear losses. All observed behaviors are robust over wide parameter regimes, making them promising for technological applications. We present ten experimental observations which span all categories of dynamical behavior previously theoretically predicted to be observable. This represents a complete experimental verification of the CQCGL equation as a model for the study of fundamental, complex nonlinear dynamics for driven, damped waves evolving in nonlinear, dispersive systems. The reported dynamical pattern formation of self-generated dark solitary waves in attractive nonlinearity without external sources or potentials, however, is entirely novel and is presented for both the periodic breather and complex recurrence behaviors.

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46

Rechcińska, Katarzyna, Mateusz Król, Rafał Mazur, Przemysław Morawiak, Rafał Mirek, Karolina Łempicka, Witold Bardyszewski, et al. "Engineering spin-orbit synthetic Hamiltonians in liquid-crystal optical cavities." Science 366, no. 6466 (November 7, 2019): 727–30. http://dx.doi.org/10.1126/science.aay4182.

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Spin-orbit interactions lead to distinctive functionalities in photonic systems. They exploit the analogy between the quantum mechanical description of a complex electronic spin-orbit system and synthetic Hamiltonians derived for the propagation of electromagnetic waves in dedicated spatial structures. We realize an artificial Rashba-Dresselhaus spin-orbit interaction in a liquid crystal–filled optical cavity. Three-dimensional tomography in energy-momentum space enabled us to directly evidence the spin-split photon mode in the presence of an artificial spin-orbit coupling. The effect is observed when two orthogonal linear polarized modes of opposite parity are brought near resonance. Engineering of spin-orbit synthetic Hamiltonians in optical cavities opens the door to photonic emulators of quantum Hamiltonians with internal degrees of freedom.

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Hardy, Matthias, Niklas Struch, Julian J. Holstein, Gregor Schnakenburg, Norbert Wagner, Marianne Engeser, Johannes Beck, Guido H. Clever, and Arne Lützen. "Dynamic Complex‐to‐Complex Transformations of Heterobimetallic Systems Influence the Cage Structure or Spin State of Iron(II) Ions." Angewandte Chemie International Edition 59, no. 8 (February 17, 2020): 3195–200. http://dx.doi.org/10.1002/anie.201914629.

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48

Stass, Dmitri V. "Geometrization for Energy Levels of Isotropic Hyperfine Hamiltonian Block and Related Central Spin Problems for an Arbitrarily Complex Set of Spin-1/2 Nuclei." International Journal of Molecular Sciences 23, no. 23 (December 2, 2022): 15199. http://dx.doi.org/10.3390/ijms232315199.

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Description of interacting spin systems relies on understanding the spectral properties of the corresponding spin Hamiltonians. However, the eigenvalue problems arising here lead to algebraic problems too complex to be analytically tractable. This is already the case for the simplest nontrivial (Kmax−1) block for an isotropic hyperfine Hamiltonian for a radical with spin-12 nuclei, where n nuclei produce an n-th order algebraic equation with n independent parameters. Systems described by such blocks are now physically realizable, e.g., as radicals or radical pairs with polarized nuclear spins, appear as closed subensembles in more general radical settings, and have numerous counterparts in related central spin problems. We provide a simple geometrization of energy levels in this case: given n spin-12 nuclei with arbitrary positive couplings ai, take an n-dimensional hyper-ellipsoid with semiaxes ai, stretch it by a factor of n+1 along the spatial diagonal (1, 1, …, 1), read off the semiaxes of thus produced new hyper-ellipsoid qi, augment the set {qi} with q0=0, and obtain the sought n+1 energies as Ek=−12qk2+14∑iai. This procedure provides a way of seeing things that can only be solved numerically, giving a useful tool to gain insights that complement the numeric simulations usually inevitable here, and shows an intriguing connection to discrete Fourier transform and spectral properties of standard graphs.

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49

Şaka, Irfan, and Azmi Gençten. "A Theoretical Application of MAXY NMR for CDn Groups." Zeitschrift für Naturforschung A 62, no. 5-6 (June 1, 2007): 259–64. http://dx.doi.org/10.1515/zna-2007-5-605.

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Liquid-state NMR experiments including edited-pulse angles are widely used to distinguish protonated and deuterated carbonyl groups in complex molecules. One of them is maximum quantum correlation NMR spectroscopy (MAXY NMR), which is very suitable to separate CHn groups. The product operator theory is used for the analytical description of these experiments for weakly coupled spin systems. In this study, the MAXY NMR experiment is applied for weakly coupled ISn (I = 1/2; S = 1; n = 1, 2, 3) spin systems using the product operator theory. A theoretical discussion and experimental suggestions for sub-spectral editing of CDn groups are also presented.

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50

Coey, J. M. D. "Noncollinear spin structures." Canadian Journal of Physics 65, no. 10 (October 1, 1987): 1210–32. http://dx.doi.org/10.1139/p87-197.

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A survey of experimental results on noncollinear spin structures in crystalline and amorphous ionic materials is given. The occurrence of coherent helical, triangular, and canted structures in pure crystals is related to the presence of competing interactions: topologically frustrated antiferromagnetic superexchange, positive and negative exchange coupling with different shells of neighbours, symmetric and antisymmetric exchange, or exchange and single-ion anisotropy. These ideas are extended to crystal surfaces, disordered crystals, mixed crystals, amorphous compounds, and complex multicomponent glasses. Random noncollinear structures found in all these materials are due to randomly competing interactions. A distinction is made between isotropic random structures, where spin correlations are very short-ranged in all directions, and those structures where comparatively long-range longitudinal ferro-, antiferro-, or ferrimagnetic correlations coexist with transverse spin freezing having correlations only on the scale of nearest neighbour distances. A generalized magnetic phase diagram for diluted random magnets is presented. It is emphasized that important aspects of those systems now known as "reentrant spin glasses" had already been described in diamagnetically substituted ferrites many years previously.

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