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Journal articles on the topic 'Quantum mixed spin'

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Author: Grafiati

Published: 10 March 2023

Last updated: 11 March 2023

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1

Geiger, Davi, and Zvi M. Kedem. "Spin Entropy." Entropy 24, no. 9 (September 14, 2022): 1292. http://dx.doi.org/10.3390/e24091292.

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Two types of randomness are associated with a mixed quantum state: the uncertainty in the probability coefficients of the constituent pure states and the uncertainty in the value of each observable captured by the Born’s rule probabilities. Entropy is a quantification of randomness, and we propose a spin-entropy for the observables of spin pure states based on the phase space of a spin as described by the geometric quantization method, and we also expand it to mixed quantum states. This proposed entropy overcomes the limitations of previously-proposed entropies such as von Neumann entropy which only quantifies the randomness of specifying the quantum state. As an example of a limitation, previously-proposed entropies are higher for Bell entangled spin states than for disentangled spin states, even though the spin observables are less constrained for a disentangled pair of spins than for an entangled pair. The proposed spin-entropy accurately quantifies the randomness of a quantum state, it never reaches zero value, and it is lower for entangled states than for disentangled states.

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2

Takano, Ken'ichi. "Disordered Phases in Mixed Quantum Spin Chains." Progress of Theoretical Physics Supplement 145 (2002): 170–75. http://dx.doi.org/10.1143/ptps.145.170.

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3

Zhang, Pan-Pan, Jie Wang, Yu-Liang Xu, Chun-Yang Wang, and Xiang-Mu Kong. "Quantum Entanglements in mixed-spin XY systems." Physica A: Statistical Mechanics and its Applications 566 (March 2021): 125643. http://dx.doi.org/10.1016/j.physa.2020.125643.

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4

Hao, Xiang, and Shiqun Zhu. "Entanglement in a quantum mixed-spin chain." Physics Letters A 366, no. 3 (June 2007): 206–10. http://dx.doi.org/10.1016/j.physleta.2007.01.053.

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5

Li, Junyao, Xiaofeng Liu, Lingyun Wan, Xinming Qin, Wei Hu, and Jinlong Yang. "Mixed magnetic edge states in graphene quantum dots." Multifunctional Materials 5, no. 1 (January 10, 2022): 014001. http://dx.doi.org/10.1088/2399-7532/ac44fe.

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Abstract Graphene quantum dots (GQDs) exhibit abundant magnetic edge states with promising applications in spintronics. Hexagonal zigzag GQDs possess a ground state with an antiferromagnetic (AFM) inter-edge coupling, followed by a metastable state with ferromagnetic (FM) inter-edge coupling. By analyzing the Hubbard model and performing large-scale spin-polarized density functional theory calculations containing thousands of atoms, we predict a series of new mixed magnetic edge states of GQDs arising from the size effect, namely mix-n, where n is the number of spin arrangement parts at each edge, with parallel spin in the same part and anti-parallel spin between adjacent parts. In particular, we demonstrate that the mix-2 state of bare GQDs (C 6 N 2 ) appears when N ⩾ 4 and the mix-3 state appears when N ⩾ 6 , where N is the number of six-membered-ring at each edge, while the mix-2 and mix-3 magnetic states appear in the hydrogenated GQDs with N = 13 and N = 15, respectively.

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6

FAN, HONGWEI, ZHAOXIN XU, and HEPING YING. "QUANTUM MONTE CARLO STUDY ON RANDOM BOND MIXED-SPIN CHAIN." International Journal of Modern Physics B 21, no. 23n24 (September 30, 2007): 4196–200. http://dx.doi.org/10.1142/s0217979207045402.

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The effects of bond randomness on the quantum mixed-spin chain 1-1-1/2-1/2 are investigated by a quantum Monte Carlo study. We find that around the critical point of original pure system, quantum Griffiths phases appears, and its region is enlarged with increasing of bond randomness. Moreover, the critical behavior of the original quantum critical point has been changed by the randomness.

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7

Batle, J., M. Abutalib, S. Abdalla, and Ahmed Farouk. "Revival of Bell nonlocality across a quantum spin chain." International Journal of Quantum Information 14, no. 07 (October 2016): 1650037. http://dx.doi.org/10.1142/s0219749916500374.

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The transmission of pure and mixed states along a quantum spin chain is investigated. Nonlocality between two qubits will evolve as it is transmitted through the quantum channel in a way that may violate or not the Clauser–Horne–Shimony–Holt (CHSH) Bell inequality at different times. This violation of local realism is analogue to the so-called sudden death and sudden birth features of entanglement. In the quantum channel, which will turn to be a damping one, some (mixed) states will be preferred according to the nature of the quantum correlations that are preserved during the evolution along the spin chain.

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8

Brieskorn, G., and K. D. Usadel. "Quantum spin glasses with randomly mixed uniaxial anisotropies." Journal of Physics C: Solid State Physics 19, no. 18 (June 30, 1986): 3413–20. http://dx.doi.org/10.1088/0022-3719/19/18/013.

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9

Wang, Jin Tong, Aaron X. Kan, and J. D. Fan. "The origin of the spooky behavior of quantum particles: Time reversal." Modern Physics Letters A 34, no. 25 (August 20, 2019): 1950199. http://dx.doi.org/10.1142/s0217732319501992.

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In this paper, we study the origin of the quantum particle entanglement. Particles will have one mixed wave function as soon as they are created, which are called quantum particle entanglement. Electron spin states are used as an example to discuss this topic. When two electrons are created simultaneously, they have two different mixed quantum spin states. Before the measurement of its spin, we cannot determine its spin state. However, as soon as the spin of one of the electrons is determined (measured), the spin of the other will definitely be in the opposite state, regardless of how far they are away from each other. This paper uses the mechanism that the wave packet spreads as soon as they are created and then the wave packet shrinks when it undergoes a measurement to interpret this spooky phenomenon mentioned above.

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10

Sakai, T., T. Tonegawa, and K. Okamoto. "Quantum magnetization plateau of an anisotropic mixed spin chain." Journal of Physics: Conference Series 51 (November 1, 2006): 163–66. http://dx.doi.org/10.1088/1742-6596/51/1/037.

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11

Berger, Michael, Dominik Schulz, and Jamal Berakdar. "Spin-Resolved Quantum Scars in Confined Spin-Coupled Two-Dimensional Electron Gas." Nanomaterials 11, no. 5 (May 11, 2021): 1258. http://dx.doi.org/10.3390/nano11051258.

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Quantum scars refer to an enhanced localization of the probability density of states in the spectral region with a high energy level density. Scars are discussed for a number of confined pure and impurity-doped electronic systems. Here, we studied the role of spin on quantum scarring for a generic system, namely a semiconductor-heterostructure-based two-dimensional electron gas subjected to a confining potential, an external magnetic field, and a Rashba-type spin-orbit coupling. Calculating the high energy spectrum for each spin channel and corresponding states, as well as employing statistical methods known for the spinless case, we showed that spin-dependent scarring occurs in a spin-coupled electronic system. Scars can be spin mixed or spin polarized and may be detected via transport measurements or spin-polarized scanning tunneling spectroscopy.

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12

Sabi Takou, D., M. Karimou, F. Hontinfinde, and E. Albayrak. "Anisotropic Heisenberg model for the mixed spin-3/2 and spin-1/2 under random crystal field." Condensed Matter Physics 24, no. 1 (March 2021): 13704. http://dx.doi.org/10.5488/cmp.24.13704.

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Thermodynamic properties of the mixed spin-3/2 and spin-1/2 Heisenberg model are examined within the Oguchi approximation in the presence of a random crystal-field (RCF). The RCF is either introduced with probability p or turned off with probability 1-p randomly. The thermal variations of the global magnetization and free energy of the system are investigated to construct the phase diagrams for the classical, quantum and anisotropic cases. Different results revealed that no qualitative changes exist between them. Quantum effects are found to be present and abundant in the quantum model in the negative D -range. This phenomenon has a strong decreasing effect on the critical temperature which becomes much lower than in the classical case. In the presence of an external field, it was observed that coercivity and remanence decrease in a wide range of the absolute temperature.

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13

Sánchez-de-Armas, Rocío, and Carmen J. Calzado. "Spin-crossover Fe(ii) complexes on a surface: a mixture of low-spin and high-spin molecules at low temperature from quantum-chemistry calculations." Inorganic Chemistry Frontiers 9, no. 4 (2022): 753–60. http://dx.doi.org/10.1039/d1qi01487k.

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The deposition of a 2D monolayer of an Fe(ii) SCO complex on Au(111) is studied by quantum chemistry calculations. The results indicate that there exists thermodynamic and kinetic factors favoring the presence of the mixed HS/LS state at low temperature.

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14

Palii, Andrew, Juan Modesto Clemente-Juan, Andrey Rybakov, Sergey Aldoshin, and Boris Tsukerblat. "Exploration of the double exchange in quantum cellular automata: proposal for a new class of cells." Chemical Communications 56, no. 73 (2020): 10682–85. http://dx.doi.org/10.1039/d0cc04135a.

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We propose to extend the class of systems suitable as cells for quantum cellular automata by including magnetic quantum dots and molecular mixed valence dimers to employ both charges and spin degrees of freedom.

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15

Batchelor, M. T., X. W. Guan, N. Oelkers, and Z. J. Ying. "Quantum Phase Diagram of an Exactly Solved Mixed Spin Ladder." Journal of Statistical Physics 116, no. 1-4 (August 2004): 571–89. http://dx.doi.org/10.1023/b:joss.0000037225.79748.98.

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16

Wu, X. G., G. Dev, and J. K. Jain. "Mixed-spin incompressible states in the fractional quantum Hall effect." Physical Review Letters 71, no. 1 (July 5, 1993): 153–56. http://dx.doi.org/10.1103/physrevlett.71.153.

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17

Zheludev, A., S. Maslov, T. Yokoo, S. Raymond, S. E. Nagler, and J. Akimitsu. "Quantum and classical dynamics in mixed-spin one-dimensional antiferromagnets." Journal of Physics: Condensed Matter 13, no. 27 (June 25, 2001): R525—R536. http://dx.doi.org/10.1088/0953-8984/13/27/202.

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18

Ma, Y. Q., and Y. G. Ma. "The Quantum Transverse Mixed Ising System with Arbitrary Spin Magnitude." physica status solidi (b) 177, no. 2 (June 1, 1993): K77—K81. http://dx.doi.org/10.1002/pssb.2221770238.

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19

Hu, Guo-Jin, and Xiu-Xia Hu. "Spin Squeezing and Quantum Fisher Information for Mixed Hamiltonian Model." International Journal of Theoretical Physics 53, no. 2 (September 26, 2013): 533–37. http://dx.doi.org/10.1007/s10773-013-1837-3.

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20

Zad, Hamid Arian, and Hossein Movahhedian. "Classical correlation and quantum entanglement in the mixed-spin Ising-XY model with Dzyaloshinskii–Moriya interaction." International Journal of Modern Physics B 31, no. 13 (February 9, 2017): 1750094. http://dx.doi.org/10.1142/s0217979217500941.

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In the present work, initially, a mixed-three-spin (1/2,1,1/2) cell of a mixed-[Formula: see text]-spin chain with Ising-XY model is introduced, for which pair spins (1,1/2) have Ising-type interaction and pair spins (1/2,1/2) have both XY-type and Dzyaloshinskii–Moriya (DM) interactions together. An external homogeneous magnetic field [Formula: see text] is considered for the system in thermal equilibrium. Integer-spins have a single-ion anisotropy property with coefficient [Formula: see text]. Then, we investigate the quantum entanglement between half-spins (1/2,1/2), by means of the concurrence. Classical correlation (CC) for this pair of spins is investigated as well as the concurrence and some interesting temperature, the magnetic field and the DM interaction properties are expressed. Moreover, single-ion anisotropy effects on the correlation between half-spins is verified. According to the verifications based on the communication channels category by Rossini, Giovannetti and Fazio [D. Rossini, V. Giovannetti and R. Fazio, Int. J. Quantum Inf. 5, 439 (2007)], we theoretically consider such tripartite spin model as an ideal quantum channel, then calculate its information transmission rate and express some differences in behavior between this suggested model and introduced simple models in the previous works (chains without spin integer and DM interaction) from information transferring protocol point of view.

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21

Chandra, P., and P. Coleman. "TWISTED MAGNETS AND TWISTED SUPERFLUIDS." International Journal of Modern Physics B 03, no. 12 (December 1989): 1729–53. http://dx.doi.org/10.1142/s0217979289001111.

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We present a quantum fluids approach to incommensurate magnetic structures, emphasizing the close analogies between spin and neutral superfluidity. In particular we show that in twisted magnets the spin superfluid phase stiffness determines the long-wavelength behavior, and that there exists the spin analogue of the roton. We conclude with a brief discussion of charge fluctuation effects, and the possibility of twisted superconductors with mixed parity pairs.

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22

Koga, Akihisa, Seiya Kumada, and Norio Kawakami. "Quantum Phase Transitions in Two-Dimensional Spin Systems with Ladder, Plaquette and Mixed-Spin Structures." Journal of the Physical Society of Japan 68, no. 7 (July 15, 1999): 2373–79. http://dx.doi.org/10.1143/jpsj.68.2373.

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23

Long, Yang, Jie Ren, and Hong Chen. "Intrinsic spin of elastic waves." Proceedings of the National Academy of Sciences 115, no. 40 (September 18, 2018): 9951–55. http://dx.doi.org/10.1073/pnas.1808534115.

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Unveiling spins of physical systems usually gives people a fundamental understanding of the geometrical properties of waves from classical to quantum aspects. A great variety of research has shown that transverse waves can possess nontrivial spins and spin-related properties naturally. However, until now, we still lack essential physical insights about the spin nature of longitudinal waves. Here, demonstrated by elastic waves, we uncover spins for longitudinal waves and the mixed longitudinal–transverse waves that play essential roles in spin–momentum locking. Based on this spin perspective, several abnormal phenomena beyond pure transverse waves are attributed to the hybrid spin induced by mixed longitudinal–transverse waves. The unique hybrid spin reveals the complex spin essence in elastic waves and advances our understanding about their fundamental geometrical properties. We also show that these spin-dependent phenomena can be exploited to control the wave propagation, such as nonsymmetric elastic wave excitation by spin pairs, a unidirectional Rayleigh wave, and spin-selected elastic wave routing. These findings are generally applicable for wave cases with longitudinal and transverse components.

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24

MATERDEY, TOMAS B. "GRAND CANONICAL MIXED-STATE WIGNER FUNCTION IN A MAGNETIC FIELD: de HAAS–van ALPHEN OSCILLATIONS." International Journal of Modern Physics B 21, no. 06 (March 10, 2007): 829–55. http://dx.doi.org/10.1142/s0217979207036680.

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Kohn proved in 1961 that interactions between electrons did not change the de Haas–van Alphen (dHvA) oscillation frequency for single electrons in the nondegenerate ground-state [Phys. Rev.123(4), 1242 (1961)]. It was proved recently that the pure-state Wigner function for an electron in a magnetic field carries this quantum and physical oscillation, and a quantum dielectric function, so the conductance can be calculated from the Wigner function [Int. J. Mod. Phys. B17(25), 4555 (2003)], [Int. j. Mod. Phys. B17(26), 4683 (2003)]. We present the first complete proof that at a finite temperature, the mixed-state Wigner function also shows dHvA oscillations with the same frequency. The Wigner function is a fundamental quantity, the fact that it carries observable physical information shows a great potential in the design of new quantum materials at the nanoscale. The definition of the mixed-state Wigner function involves a grand canonical partition function (GCPF). Although dHvA is a well-known phenomenon, we present the first complete proof of it happening in degenerate mixed-states, based on a GCPF, which requires reconciliation between the dHvA experimental condition of a fixed number of particles and the GCPF's sum over number of particles. The GCPF is applied to one of the two spin species, while both the spin and spin-magnetic moment interaction are considered. We show that the contour integration in ω(ε) leads to a non-oscillatory term that is much larger than an oscillatory term, in the dHvA experimental conditions of high fields and low temperatures. This dominance of the non-oscillatory term explains the constancy of the chemical potential, allowing it to reduce to the Fermi energy in the limit of zero temperature. The obtained mixed-state Wigner function shows a fundamental period of oscillation with respect to B-1 that reduces to the Onsager's period for dHvA oscillations. This indicates that in mixed-states, dHvA oscillations depend on electrons of one spin species, this means the population of electrons of each spin species oscillates with the magnetic field. The temperature dependence in the Wigner function will allow a combination of phase-space and thermodynamics information for mesoscopic structures, and the study of phase-space density holes such as BGK modes in the quantum domain.

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25

SANCTUARY, B. C. "CORRELATIONS IN ENTANGLED STATES." International Journal of Modern Physics B 20, no. 11n13 (May 20, 2006): 1496–503. http://dx.doi.org/10.1142/s0217979206034078.

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Entangled EPR spin pairs can be treated using the statistical ensemble interpretation of quantum mechanics. As such the singlet state results from an ensemble of spin pairs each with its own specific axis of quantization. This axis acts like a quantum mechanical hidden variable. If the spins lose coherence they disentangle into a mixed state that contains classical correlations. In this paper an infinitesimal phase decoherence is introduced to the singlet state in order to reveal more clearly some of the correlations. It is shown that a singlet state has no classical correlations.

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26

Palii, Andrew, Juan Modesto Clemente-Juan, Andrey Rybakov, Sergey Aldoshin, and Boris Tsukerblat. "Toward multifunctional molecular cells for quantum cellular automata: exploitation of interconnected charge and spin degrees of freedom." Physical Chemistry Chemical Physics 23, no. 26 (2021): 14511–28. http://dx.doi.org/10.1039/d1cp00444a.

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We discuss a possibility of using mixed-valence dimers comprising paramagnetic metal ions as molecular cells for quantum cellular automata. Charge distributions in these systems encode binary information with additional option of spin switching.

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27

SARKAR, SUJIT. "QUANTUM PHASE ANALYSIS OF AN ANISOTROPIC (XYZ) HEISENBERG SPIN-1/2 CHAIN UNDER A UNIFORM AND STAGGERED MAGNETIC FIELD." International Journal of Modern Physics B 23, no. 16 (June 30, 2009): 3363–68. http://dx.doi.org/10.1142/s0217979209052819.

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We study quantum phases of an anisotropic (XYZ) Heisenberg spin-1/2 chain under a mixed magnetic field (uniform and staggered), along with its variant. Our model consists of two competing relevant operators, anisotropy a, and staggered magnetic field hs. Depending on the sign of a this model describes either the physics of solitonic confinement, or the Ising transition between gapped phases. In our case excitations are the integer spin particle in contrast to the half-integer spin particle of frustrated dimerized spin chain. We do all analysis in weak coupling limit.

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28

Gálisová, Lucia, and Michał Kaczor. "Ground State, Magnetization Process and Bipartite Quantum Entanglement of a Spin-1/2 Ising–Heisenberg Model on Planar Lattices of Interconnected Trigonal Bipyramids." Entropy 23, no. 12 (December 12, 2021): 1671. http://dx.doi.org/10.3390/e23121671.

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The ground state, magnetization scenario and the local bipartite quantum entanglement of a mixed spin-1/2 Ising–Heisenberg model in a magnetic field on planar lattices formed by identical corner-sharing bipyramidal plaquettes is examined by combining the exact analytical concept of generalized decoration-iteration mapping transformations with Monte Carlo simulations utilizing the Metropolis algorithm. The ground-state phase diagram of the model involves six different phases, namely, the standard ferrimagnetic phase, fully saturated phase, two unique quantum ferrimagnetic phases, and two macroscopically degenerate quantum ferrimagnetic phases with two chiral degrees of freedom of the Heisenberg triangular clusters. The diversity of ground-state spin arrangement is manifested themselves in seven different magnetization scenarios with one, two or three fractional plateaus whose values are determined by the number of corner-sharing plaquettes. The low-temperature values of the concurrence demonstrate that the bipartite quantum entanglement of the Heisenberg spins in quantum ferrimagnetic phases is field independent, but twice as strong if the Heisenberg spin arrangement is unique as it is two-fold degenerate.

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29

ZHANG, GUANG-MING, ZHAO-BIN SU, and LU YU. "NON-FERMI LIQUID BEHAVIOR IN THE SINGLE-IMPURITY MIXED VALENCE PROBLEM." Modern Physics Letters B 09, no. 23 (October 10, 1995): 1527–33. http://dx.doi.org/10.1142/s0217984995001522.

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An effective Hamiltonian of the Anderson single-impurity model with finite-range Coulomb interactions is derived near a particular limit, which is analogous to the Toulouse limit of the ordinary Kondo problem, and the physical properties around the mixed valence quantum critical point are calculated. At this quantum critical point, the local moment is only partially quenched and X-ray edge singularities are exhibited. Around this point, a new type of non-Fermi liquid behavior is predicted with an extra specific heat C imp ~ T1/4 + AT ln T and spin-susceptibility χ imp ~T−3/4 + B ln T.

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30

LI, XIAO-JING, HUI-HUI JI, and XI-WEN HOU. "THERMAL DISCORD AND NEGATIVITY IN A TWO-SPIN-QUTRIT SYSTEM UNDER DIFFERENT MAGNETIC FIELDS." International Journal of Quantum Information 11, no. 08 (December 2013): 1350070. http://dx.doi.org/10.1142/s0219749913500706.

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The characterization of quantum discord (QD) has been well understood only for two-qubit states and is little known for mixed states beyond qubits. In this work, thermal quantum discord is studied for a qutrit system in different magnetic fields, where classical correlation and entanglement negativity are calculated for comparison. It is shown that the discord is more robust against temperature than the negativity. For a suitable region of magnetic field and its direction, the discord is non-zero while the negativity is zero. When the system is at a lower temperature, these three quantities, however, display a similar behavior for the varied field and direction, and their discontinuities come from crossovers between different ground states in the system. Moreover, the inequality between the quantum and classical correlations depends upon the system parameters as well as the temperature. In particular, both correlations are equal at a suitable field, direction, and temperature. Remarkably, such an equality remains for a strong field in the antiparallel direction, while both correlations in two-qubit systems are identical for any antiparallel field and temperature. These are useful for quantum information and understanding quantum correlations in qutrit mixed states.

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31

LI, JUN, GUOZHU WEI, and AN DU. "COMPENSATION TEMPERATURE OF A MIXED SPIN-1 AND SPIN-1/2 HEISENBERG FERRIMAGNETIC MODEL." International Journal of Modern Physics B 18, no. 10n11 (April 30, 2004): 1637–49. http://dx.doi.org/10.1142/s0217979204024963.

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The behavior of the compensation of a mixed spin-1 and spin-1/2 Heisenberg ferrimagnetic system on a square lattice is investigated theoretically by a two-time Green-function technique which takes into account the quantum nature of Heisenberg spins. The model includes the nearest and next-nearest neighbor interactions between spins, a crystal field and an external magnetic field. This model can be relevant for understanding the magnetic behavior of bimetallic molecular ferrimagnets that are currently being synthesized by several experimental groups. We study the spin-wave spectra of the ground state and investigate the effects of the next-nearest neighbor interactions, a crystal field and an external magnetic field on the compensation temperature. It is found that a compensation point appears and it is basically unchanged when the next-nearest-neighbor interaction between spin-1/2 is taken into account and exceeds a minimum value for other values in Hamiltonian fixed. The compensation temperature is influenced by the next-nearest-neighbor interaction between spin-1 and the external magnetic field and it is disappearing as these parameters exceed the trivial values.

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32

Tsukerblat, Boris, Andrew Palii, and Sergey Aldoshin. "In Quest of Molecular Materials for Quantum Cellular Automata: Exploration of the Double Exchange in the Two-Mode Vibronic Model of a Dimeric Mixed Valence Cell." Magnetochemistry 7, no. 5 (May 12, 2021): 66. http://dx.doi.org/10.3390/magnetochemistry7050066.

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In this article, we apply the two-mode vibronic model to the study of the dimeric molecular mixed-valence cell for quantum cellular automata. As such, we consider a multielectron mixed valence binuclear d2−d1–type cluster, in which the double exchange, as well as the Heisenberg-Dirac-Van Vleck exchange interactions are operative, and also the local (“breathing”) and intercenter vibrational modes are taken into account. The calculations of spin-vibronic energy spectra and the “cell-cell”-response function are carried out using quantum-mechanical two-mode vibronic approach based on the numerical solution of the dynamic vibronic problem. The obtained results demonstrate a possibility of combining the function of molecular QCA with that of spin switching in one electronic device and are expected to be useful from the point of view of the rational design of such multifunctional molecular electronic devices.

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33

Gupta, Kumar S., and Amilcar de Queiroz. "Anomalies and renormalization of mixed states in quantum theories." Modern Physics Letters A 29, no. 13 (April 30, 2014): 1450064. http://dx.doi.org/10.1142/s0217732314500643.

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In a Hamiltonian approach to anomalies, parity and time-reversal symmetries can be restored by introducing suitable impure (or mixed) states. However, the expectation values of observables such as the Hamiltonian diverges in such impure states. Here, we show that such divergent expectation values can be treated within a renormalization group (RG) framework, leading to a set of β-functions in the moduli space of the operators representing the observables. This leads to well-defined expectation values of the Hamiltonian in a phase where the impure state restores the P and T symmetry. We also show that this RG procedure leads to a mass gap in the spectrum. Such a framework may be relevant for long wavelength descriptions of condensed matter systems such as the quantum spin Hall (QSH) effect.

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34

Arthur, Tsamouo Tsokeng, Tchoffo Martin, and Lukong Cornelius Fai. "Quantum correlations and coherence dynamics in qutrit–qutrit systems under mixed classical environmental noises." International Journal of Quantum Information 15, no. 06 (September 2017): 1750047. http://dx.doi.org/10.1142/s0219749917500472.

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We investigate the dynamics of entanglement, quantum discord (QD) and state coherence in a bipartite and noninteracting spin-qutrits system under mixed classical noises. Specifically, the collective effects of static noise (SN) and random telegraphic noise (RTN) each being coupled with a marginal system, are analyzed. While the static noise models a non-Markovian environment, the dynamic noise can model both a Markovian or a non-Markovian environment, and both dynamics are studied. We show that quantum correlations and coherence may survive the noise degrading effects at sufficiently long time when the Markovian regime of the RTN is considered. Meanwhile, the opposite is found in the non-Markovian regime, wherein the nonmonotonic dynamics of quantum features avoid sudden death phenomena. However, the static noise is more fatal to the survival of quantum correlations and quantum state coherence as compared to the RTN.

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35

JAFARIZADEH, M. A., and M. MAHDIAN. "SPIN–MOMENTUM CORRELATION IN RELATIVISTIC SINGLE-PARTICLE QUANTUM STATES." International Journal of Quantum Information 08, no. 03 (April 2010): 517–28. http://dx.doi.org/10.1142/s0219749910006125.

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This paper is concerned with the spin–momentum correlation in single-particle quantum states, which is described by the mixed states under Lorentz transformations. For convenience, instead of using the superposition of momenta we use only two momentum eigenstates (p1 and p2) that are perpendicular to the Lorentz boost direction. Consequently, in 2D momentum subspace we show that the entanglement of spin and momentum in the moving frame depends on the angle between them. Therefore, when spin and momentum are perpendicular the measure of entanglement is not an observer-dependent quantity in the inertial frame. Likewise, we have calculated the measure of entanglement (by using the concurrence) and have shown that entanglement decreases with respect to the increase in observer velocity. Finally, we argue that Wigner rotation is induced by Lorentz transformations and can be realized as a controlling operator.

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36

Claes, Jahan, and Wim van Dam. "Instance Independence of Single Layer Quantum Approximate Optimization Algorithm on Mixed-Spin Models at Infinite Size." Quantum 5 (September 15, 2021): 542. http://dx.doi.org/10.22331/q-2021-09-15-542.

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This paper studies the application of the Quantum Approximate Optimization Algorithm (QAOA) to spin-glass models with random multi-body couplings in the limit of a large number of spins. We show that for such mixed-spin models the performance of depth 1 QAOA is independent of the specific instance in the limit of infinite sized systems and we give an explicit formula for the expected performance. We also give explicit expressions for the higher moments of the expected energy, thereby proving that the expected performance of QAOA concentrates.

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Schneider, Benjamin, Serhiy Demeshko, Sven Neudeck, Sebastian Dechert, and Franc Meyer. "Mixed-Spin [2 × 2] Fe4 Grid Complex Optimized for Quantum Cellular Automata." Inorganic Chemistry 52, no. 22 (October 25, 2013): 13230–37. http://dx.doi.org/10.1021/ic4021838.

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38

Teki, Yoshio, and Takafumi Matsumoto. "Spin dynamics on photoexcited state of functionality π-radical via quantum-mixed state: Theoretical study of the spin polarized state generation using the mechanism via quantum-mixed state." Synthetic Metals 173 (June 2013): 35–39. http://dx.doi.org/10.1016/j.synthmet.2012.12.005.

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39

Yang, Sheng, and Jing‐Bo Xu. "Quantum Phase Transition of a Quantum Mixed Spin Chain by Employing Density Matrix Renormalization Group Method." Annalen der Physik 533, no. 5 (March 31, 2021): 2100011. http://dx.doi.org/10.1002/andp.202100011.

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40

Falson, Joseph, Daniela Tabrea, Ding Zhang, Inti Sodemann, Yusuke Kozuka, Atsushi Tsukazaki, Masashi Kawasaki, Klaus von Klitzing, and Jurgen H. Smet. "A cascade of phase transitions in an orbitally mixed half-filled Landau level." Science Advances 4, no. 9 (September 2018): eaat8742. http://dx.doi.org/10.1126/sciadv.aat8742.

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Half-filled Landau levels host an emergent Fermi liquid that displays instability toward pairing, culminating in a gapped even-denominator fractional quantum Hall ground state. While this pairing may be probed by tuning the polarization of carriers in competing orbital and spin degrees of freedom, sufficiently high quality platforms offering such tunability remain few. We explore the ground states at filling factor ν = 5/2 in ZnO-based two-dimensional electron systems through a forced intersection of opposing spin branches of Landau levels taking quantum numbers N = 1 and 0. We reveal a cascade of phases with distinct magnetotransport features including a gapped phase polarized in the N = 1 level and a compressible phase in N = 0, along with an unexpected Fermi liquid, a second gapped, and a strongly anisotropic nematic-like phase at intermediate polarizations when the levels are near degeneracy. The phase diagram is produced by analyzing the proximity of the intersecting levels and highlights the excellent reproducibility and controllability that ZnO offers for exploring exotic fractionalized electronic phases.

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MIZRAHI, S. S., V. V. DODONOV, and D. OTERO. "A COMPARISON BETWEEN WEHRL–LIEB AND VON NEUMANN ENTROPIES FOR TIME-EVOLVING SPIN-1/2 MIXED STATES." Modern Physics Letters B 08, no. 16 (July 10, 1994): 995–1006. http://dx.doi.org/10.1142/s021798499400100x.

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Years ago, A. Wehrl (Rev. Mod. Phys.50, 221 (1978)) introduced the concept of classicallike entropy of quantum states when a two-label continuous representation is used; for instance, the harmonic oscillator coherent states. Subsequently, E. H. Lieb (Commun. Math. Phys.62, 35 (1978)) extended that concept of entropy to the Bloch coherent spin states. Here, we consider spin-1/2 systems and calculate both the Wehrl–Lieb and von Neumann entropies, and then we compare the results and discuss the Wehrl–Lieb entropy as an alternative formulation to von Neumann's. As illustration, three examples are worked out: (i) the decoherence of a quantum state in a measurement process, (ii) the conservation of coherence, and (iii) the recoherence phenomena that appear in the solutions of a specific master equation that originates from a nonlinear Schrödinger equation.

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42

Vargová, Hana, and Jozef Strečka. "Unconventional Thermal and Magnetic-Field-Driven Changes of a Bipartite Entanglement of a Mixed Spin-(1/2,S) Heisenberg Dimer with an Uniaxial Single-Ion Anisotropy." Nanomaterials 11, no. 11 (November 16, 2021): 3096. http://dx.doi.org/10.3390/nano11113096.

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The concept of negativity is adapted in order to explore the quantum and thermal entanglement of the mixed spin-(1/2,S) Heisenberg dimers in presence of an external magnetic field. The mutual interplay between the spin size S, XXZ exchange and uniaxial single-ion anisotropy is thoroughly examined with a goal to tune the degree and thermal stability of the pairwise entanglement. It turns out that the antiferromagnetic spin-(1/2,S) Heisenberg dimers exhibit higher degree of entanglement and higher threshold temperature in comparison with their ferromagnetic counterparts when assuming the same set of model parameters. The increasing spin magnitude S accompanied with an easy-plane uniaxial single-ion anisotropy can enhance not only the thermal stability but simultaneously the degree of entanglement. It is additionally shown that the further enhancement of a bipartite entanglement can be achieved in the mixed spin-(1/2,S) Heisenberg dimers, involving half-odd-integer spins S. Under this condition the thermal negativity saturates at low-enough temperatures in its maximal value regardless of the magnitude of half-odd-integer spin S. The magnetic field induces consecutive discontinuous phase transitions in the mixed spin-(1/2,S) Heisenberg dimers with S>1, which are manifested in a surprising oscillating magnetic-field dependence of the negativity observed at low enough temperature.

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43

Ang, Joo Chuan, Yanyan Mulyana, Chris Ritchie, Rodolphe Clérac, and Colette Boskovic. "Mixed-Valent Polynuclear Cobalt Complexes Incorporating Tetradentate Phenoxyamine Ligands." Australian Journal of Chemistry 62, no. 9 (2009): 1124. http://dx.doi.org/10.1071/ch09256.

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The new potentially tetradentate ligand precursor 2-[(bis(2-hydroxyethyl)amino)methyl]-4,6-bis-tert-butylphenol (H3L) has been synthesized and characterized. The reaction of H3L with cobalt(ii) acetate has afforded the novel mixed-valent tetra- and pentanuclear cobalt complexes [CoII2CoIII2(OAc)2(L)2(HL)] (1) and [CoIICoIII4(OAc)2(L)4] (2). Single-crystal X-ray diffraction studies of these complexes indicate different coordination geometries for the divalent cobalt centres in each complex, with distorted trigonal bipyramidal and distorted tetrahedral coordination evident in 1 and 2, respectively. The variable temperature magnetic susceptibility data for complex 1 reveal behaviour dominated by antiferromagnetic coupling between the two cobalt(ii) centres. Their approximate trigonal bipyramidal coordination geometries give rise to a 4A′2 ground term, allowing a spin-only treatment assuming local spin quantum numbers of Si = 3/2. Fitting the data to the Heisenberg exchange Hamiltonian (Ĥex = –2JS·1S2) results in J = –6.9(1) cm–1 and g = 2.30(5).

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Qin, Yan, and Sheng-Chang Li. "Quantum phase transition of a modified spin-boson model." Journal of Physics A: Mathematical and Theoretical 55, no. 14 (March 8, 2022): 145301. http://dx.doi.org/10.1088/1751-8121/ac5507.

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Abstract We adopt a modified spin-boson model to investigate the quantum phase transition in an ultracold atom-molecule conversion system involving molecule–molecule interaction. We explore the properties of ground state, entanglement entropy, and many-body dynamics, which confirm that the system exhibits a second-order phase transition from a pure atom phase to a mixed atom-molecule phase when the energy detuning is below a critical value. We obtain three scaling laws and the corresponding two critical exponents to characterize the phase transition. In particular, we discuss the effects of both the speed of ground-state dynamical evolution and the strength of molecular interaction on the phase transition. The adiabatic evolution condition is obtained as well. Our results show that the molecular interaction can greatly reduce the upper bound of the adiabatic condition, which provides a theoretical basis for easier observation of the phase transition in experiments.

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Toutounji, Mohamad. "Electronic dephasing in mixed quantum–classical molecular systems using the spin-boson model." Physica A: Statistical Mechanics and its Applications 585 (January 2022): 126385. http://dx.doi.org/10.1016/j.physa.2021.126385.

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46

Ivanov, Peter A., and Ferdinand Schmidt-Kaler. "Simulation of quantum magnetism in mixed-spin systems with impurity-doped ion crystals." New Journal of Physics 13, no. 12 (December 9, 2011): 125008. http://dx.doi.org/10.1088/1367-2630/13/12/125008.

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Aydiner, Ekrem, and Seyit Deniz Han. "Quantum heat engine model of mixed triangular spin system as a working substance." Physica A: Statistical Mechanics and its Applications 509 (November 2018): 766–76. http://dx.doi.org/10.1016/j.physa.2018.06.018.

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48

Xiong, Y. S., Y. M. Shang, L. Yi, and K. L. Yao. "Quantum Heisenberg spin-glass model with mixed-anisotropy interactions in applied magnetic fields." Journal of Physics: Condensed Matter 7, no. 14 (April 3, 1995): 2865–73. http://dx.doi.org/10.1088/0953-8984/7/14/023.

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49

Palii, Andrew, Boris Tsukerblat, Juan Modesto Clemente-Juan, and Eugenio Coronado. "Spin Switching in Molecular Quantum Cellular Automata Based on Mixed-Valence Tetrameric Units." Journal of Physical Chemistry C 120, no. 30 (July 14, 2016): 16994–7005. http://dx.doi.org/10.1021/acs.jpcc.6b02587.

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50

Bešlić, I., L. Vranješ Markić, and J. Boronat. "Quantum Monte Carlo study of small pure and mixed spin-polarized tritium clusters." Journal of Chemical Physics 128, no. 6 (February 14, 2008): 064302. http://dx.doi.org/10.1063/1.2827119.

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