Entanglement in the three-qubit Heisenberg model with next nearest neighbor interaction and a nonuniform magnetic field

We investigate the thermal entanglement of two-qubit anisotropic Heisenberg XY model in the presence of an external nonuniform magnetic field B along the z-axis. Concurrence, the measure of entanglement is calculated and its property is studied in different cases. Two best models, Ising model under a uniform magnetic and isotropic model in a nonuniform magnetic field, are discovered. In the two models, the critical temperature Tc (above which there is no entanglement) can be enhanced and its concurrence is maximal.

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COMPENSATION TEMPERATURE OF A MIXED SPIN-1 AND SPIN-1/2 HEISENBERG FERRIMAGNETIC MODEL

International Journal of Modern Physics B ◽

10.1142/s0217979204024963 ◽

2004 ◽

Vol 18 (10n11) ◽

pp. 1637-1649 ◽

Cited By ~ 1

Author(s):

JUN LI ◽

GUOZHU WEI ◽

AN DU

Keyword(s):

Magnetic Field ◽

External Magnetic Field ◽

Crystal Field ◽

Nearest Neighbor ◽

Magnetic Behavior ◽

Compensation Temperature ◽

Square Lattice ◽

Function Technique ◽

Neighbor Interaction ◽

Mixed Spin

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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SIMULATION OF A MULTICRITICAL FCC ISING ANTIFERROMAGNET

International Journal of Modern Physics C ◽

10.1142/s0129183196000703 ◽

1996 ◽

Vol 07 (06) ◽

pp. 857-861

Author(s):

D. RENNÉ

Keyword(s):

Magnetic Field ◽

Monte Carlo ◽

External Magnetic Field ◽

Triple Point ◽

Nearest Neighbor ◽

Neighbor Interaction ◽

Multicritical Point ◽

Fcc Lattice ◽

Ising Antiferromagnet ◽

Open Question

Inspired by the work by Kämmerer, Dünweg, Binder, and d'Onorio de Meo we investigated the spin-[Formula: see text] Ising antiferromagnet on a fcc lattice in a homogeneous external magnetic field H with uniform nearest-neighbor interaction J by Monte Carlo simulations. In order to answer the open question whether this system exhibits a triple point or a multicritical point for positive H, we mainly studied lattices with 4 · 323 and 4 · 723 spins. We found a multicritical point at (Hc, kBTc) = (3.49 ± 0.02, 1.02 ± 0.01) J in the thermodynamic limit.

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Entanglement and quantum spin glass

International Journal of Modern Physics B ◽

10.1142/s0217979214300126 ◽

2014 ◽

Vol 28 (20) ◽

pp. 1430012 ◽

Cited By ~ 3

Author(s):

C. Y. Koh

Keyword(s):

Magnetic Field ◽

Spin Glass ◽

General Formula ◽

Nearest Neighbor ◽

Quantum Spin ◽

Neighbor Interaction ◽

Qubit System ◽

J Coupling ◽

Xx Model ◽

Heisenberg Xx Model

The paper reviews the entanglement behavior of a 2-qubit system in a quantum spin glass using the Heisenberg XX model and the interaction of the system with a spin glass bath environment. In the first part, we study the entanglement (concurrence) for a 3- and 4-qubit with nearest neighbor interaction. With a fixed mean and varying standard deviation for the J coupling, the concurrence is numerically plotted with temperature for the different configurations. A general formula for the concurrence is given for n qubits at low temperature. In the second part, we study the concurrence of a 2-qubit system coupled to a spin glass bath environment with n = 2 to ≥ 4 qubits. The bath sites are coupled with random J coupling and varying applied magnetic field. A general formula for concurrence is given for mean J = 0 and B = 0 for n bath sites. For small random J and magnetic field B, a steady state is obtained with an approximate concurrence of 0.5, showing that the entanglement is preserved.

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Application of Bogoliubov-de Gennes equations to vortices in Hubbard superconductors

MRS Proceedings ◽

10.1557/opl.2015.158 ◽

2015 ◽

Vol 1753 ◽

Author(s):

Chumin Wang ◽

César G. Galván ◽

Luis A. Pérez

Keyword(s):

Magnetic Field ◽

Experimental Data ◽

Electron Concentration ◽

Nearest Neighbor ◽

Magnetic Vortex ◽

Superconducting Gap ◽

Electronic Specific Heat ◽

Neighbor Interaction ◽

Self Consistent ◽

Generalized Hubbard Model

ABSTRACTIn this work, the formation of d-wave superconducting magnetic vortex is studied within the Bogoliubov-de Gennes formalism and the generalized Hubbard model, which leads to 2N2 coupled self-consistent equations for a supercell of N×N atoms. These equations determine the spatial variation of the superconducting gap as a function of the electron concentration and electron-electron interactions. The results show that the superconducting states induced by the correlated hopping (Δt3) are more sensitive to the presence of magnetic field than those induced by attractive nearest-neighbor interaction (V). Furthermore, we calculate the electronic specific heat as a function of the temperature for a given applied magnetic field, whose behavior has a qualitative agreement with experimental data.

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