Thermal entanglement in two-qutrit spin-1 anisotropic Heisenberg model with inhomogeneous magnetic field

The thermal entanglement of a two-qutrit spin-1 anisotropic Heisenberg XXZ chain in an inhomogeneous magnetic field is studied in detail. The effects of the external magnetic field (B), a parameter b which controls the inhomogeneity of B, and the bilinear interaction parameters J_{x=Jy≠Jz on the thermal variation of the negativity are studied in detail. It is found that negativity N decreases when the values of magnetic field, inhomogeneity b and temperature are increasing. In addition, N remains at higher temperatures for higher values of Jz and lower values of B and b.}     

Thermal entanglement in the XYZ model for a two-qutrit system

The negativity as a measure of thermal entanglement was studied for a two-qutrit spin-1 anisotropic Heisenberg XYZ chain with Dzyaloshinskii-Moriya (DM) interaction in a homogeneous magnetic field in detail. An analytical expression was found for the negativity and then the thermal variations of negativity were investigated in full detail for given values of the DM interaction parameter D_z, the external magnetic field B, the measure of the anisotropy on the xy-plane γ = (J_x − J_y)/(J_x + J_y), a parameter J = (J_x + J_y)/2 and the bilinear interaction parameter J_z along the z-axis.     

Effects of Dzyaloshinskii-Moriya interaction on thermal entanglement and teleportation via a two-qubit Heisenberg XXZ spin chain under external magnetic field

This paper mainly investigates the effects of different Dzyaloshinskii-Moriya (DM) anisotropic antisymmetric interactions on thermal entanglement and teleportation of one-qubit state in both the standard and non-standard protocols as well as the partial teleportation of an entangled state via a two-qubit Heisenberg XXZ spin chain in the presence of external magnetic fields. The dependency of the thermal entanglement and average fidelity on various system parameters is analyzed. The interplay of the different parameters on the teleportation is discussed. The DM interaction is found to be effective for the thermal entanglement in the spin chain both with and without external magnetic fields. However, it turned out to be destructive for the teleportation in the standard protocol, whereas is found constructive for single qubit teleportation when the spin chain with the z-direction parameters is used as the channel in the non-standard protocol. Moreover, the results show that, for teleporting one-qubit state, the antiferromagnetic (AFM) chain is the only qualified candidate in the standard protocol, while both the AFM and ferromagnetic (FM) chains with the parameters along the z-axis are all suitable in the non-standard protocol when the parameters are chosen appropriately. For the partial teleportation of entanglement, both the AFM and FM chains are eligible as long as the appropriate combinations of parameters are chosen. In addition, the comparison of the effects of the same, fixed x- and z-component parameters of the DM interaction (D_x and D_z) on teleportation is presented.     

Enhancing the Trace Norm and Bures Norm Measurement-Induced Nonlocality in the Heisenberg XYZ Model

Nonlocality is one unique characteristic of quantum mechanics and an essential resource for quantum communication and computation. We investigate two measures of the well-defined geometric measurement-induced nonlocality (MIN) in the Heisenberg XYZ model, and found that considerable enhancement of the MINs can be achieved by tuning strength of the anisotropic parameter, the J_z coupling, and the Dzyaloshinsky-Moriya (DM) interaction of the model. Particularly, the maxima of the two MINs can be obtained when the strength of the J_z coupling or the DM interaction approaches infinity. We have also demonstrated the singular behaviors of the two MINs such as the nonunique states ordering and the sudden change behaviors.     

Thermal Entanglement in Anisotropic Heisenberg XYZ Chain with External Magnetic Field at Any Finite <Emphasis Type="Italic">T</Emphasis>

The thermal entanglement of a Two-qubit anisotropic Heisenberg XYZ chain in thermal equilibrium at temperature T in the presence of external magnetic field is investigated, the combined influence of anisotropic interaction and the inhomogeneous magnetic field on the thermal entanglement of the system is examined. Our results show that, the thermal entanglement can be produced at any finite T by adjusting the magnetic field strength, and the critical magnetic field ε for which the concurrence C vanishes is increased by introducing the interaction of the z-component of two neighboring spins J _z , and by the increasing of the anisotropic parameter γ.     

Quantum Monte Carlo Investigation of the magnetic properties of weakly interacting antiferromagnetic chains with an alternating exchange interaction with spin S = 1/2

An approximation dependence of the spontaneous magnetic moment at a site, σ/σ(0) ? 1 = and the antiferromagnet-singlet state phase boundary, J ₂/J ₁ = 0.52(3)δ, are determined by the quantum Monte Carlo method in the self-consistent sublattice molecular field approximation for weakly inter-acting (J ₂) antiferromagnetic chains with spin S = 1/2 and alternating exchange interaction (J ₁ ± δ). The Néél temperature and a number of critical temperatures which could be related with the filling energy of two singlets (ΔS ^z = 0) and one triplet (ΔS ^z = 1) spin bands, each of which is split by the sublattice field (h ^{x, y} ≠ h ^z into two subbands, are determined on the basis of the computed correlation radii of the two-and four-spin correlation function, the squared total spin 〈 (S ^z)²〉 with respect to the longitudinal components, the dimerization parameter, and the correlation functions between the nearest neighbors with respect to longitudinal and transverse spin components. On the basis of the Monte Carlo calculations, the critical temperatures and possible energy gaps at the band center are determined for the antiferromagnets CuWO₄ and Bi₂CuO₄ and for the singlet compounds (VO)₂P₂O₇ and CuGeO₃, agreeing satisfactorily with existing results, and new effects are also predicted.     

Thermal entanglement and teleportation in a two-qubit Heisenberg XXZ chain with different Dzyaloshinskii-Moriya interactions

We study the thermal output entanglement and teleportation in a two qubit Heisenberg XXZ chain with different Dzyaloshinskii-Moriya (DM) interactions. The analytical expressions of the output entanglement and the average fidelity are obtained for this model. We find the entanglement of replica states will be induced by some large value of D_z and the output entanglement exists for the case of J_z < − 1. The influences of the different DM interactions on the fidelity of teleportation are studied. We show that by introducing the x-component DM interaction, the average fidelity F_A can reach its maximum value 1.     

具有次近邻相互作用的五量子比特XXZ海森伯自旋链的热纠缠

研究具有次近邻相互作用五量子比特XXZ海森伯自旋链在磁场作用下的热纠缠性质,利用数值计算求出最近邻两量子比特和次近邻两量子比特的共生纠缠度(concurrence),分别记为C_(12)和C_(13).研究结果表明,阻挫参数对配对热纠缠具有重要影响,而且阻挫参数的变化对C_(12)和C_(13)的影响也各不相同;温度、磁场、Dzyaloshinkii-Moriya相互作用以及各向异性参数对配对热纠缠有着不同程度的影响;通过选择适当的模型参数,可以有效地调节和提高五量子比特XXZ海森伯自旋链的配对热纠缠.     

Correlation inequalities and the Kosterlitz-Thouless transition for anisotropic rotators

I give a proof of the Kosterlitz-Thouless transition for sufficiently anisotropic (J _zJ _x ^–1 =J _zJ _y ^–1 <2q ^–(JKT)^–J) two-dimensionalN-component rotators (N 3). The method is based on Wells' inequality and is related to mean field Gaussian inequalities.     

The temperature-dependent phase diagrams of the spin-3/2 Ising model on a FM/AFM two-layer lattice with a crystal field

The temperature-dependent phase diagrams of the spin-3/2 Ising model on a two-layer Bethe lattice with ferromagnetic (FM)/antiferromagnetic (AFM) intra-layer and either FM or AFM type inter-layer interactions are investigated under a constant magnetic field (H) and in the presence of a crystal field (D) by using exact recursion equations in a pairwise approach for coordination numbers q=3,4 and 6, in detail. In the light of the ground-state (GS) phase diagrams, the temperature-dependent phase diagrams of the model are obtained by studying the thermal variations of the order parameters, response functions and free energy. Then, they are illustrated on the (kT/J₁,J₃/J₁) and (kT/J₁,J₂/J₁) planes for the given system parameters. It is observed that the system exhibits first- and second-order phase transitions for all q values, and hence, in some cases, tricritical points. The existence of critical-end points and that of isolated points are also observed. The re-entrant behavior owes its presence to the two Néel temperatures, T_N, that are present for all q.     

Thermal Entanglement in a Two-Qubit Heisenberg XXZ Spin Chain Under a Single Pulse Magnetic Field

The thermal entanglement in a two-qubit Heisenberg XXZ spin chain is investigated under a single pulse magnetic field Bsinθ. The paper shows that the greater the contribution of the inhomogeneity on the exchange interaction, the higher thermal entanglement will be attained at the fixed temperature except the case that $\theta=2k\pi+\frac{3}{2}\pi$ . J _z  significantly disturb the thermal entanglement in uniform case. When the structure of the spin system are given, changing the external magnetic field B can induce controllable entanglement. Our study may provide a useful tool to change the entanglement of spin chain system.     

Influence of Dzyaloshinskii–Moriya interaction in the sinusoid magnetic field on the thermal quantum correlation of inhomogeneous Heisenberg spin chain

We investigate the anisotropic Heisenberg XXZ spin chain that possesses Dzyaloshinskii–Moriya (DM) interaction and discuss the behavior characteristics of the thermal quantum correlation (thermal quantum discord and thermal quantum entanglement) in the inhomogeneous magnetic field that is manipulated by sinusoidal wave. The results indicate that the DM interaction strengthens the thermal correlation such that the stronger the DM interaction is, the more obvious it strengthens. We can control the thermal correlation through externally adding an inhomogeneous magnetic field that a relative stable range can be formed where the thermal quantum correlation is almost foreign to the coupling coefficient of z-direction spin, thereby the thermal quantum correlation is controlled and enhanced.     

Dynamics of Anisotropic Bianchi Type-III Bulk Viscous String Model with Magnetic Field

In this paper, we discuss the dynamics of spatially homogeneous and anisotropic Bianchi type-III string cosmological model in presence of bulk viscous fluid and electromagnetic field. Exact solutions of Einstein’s field equations are obtained by assuming (i) a special form of the deceleration parameter and (ii) the component \(\sigma^{1}_{1}\) of the shear scalar tensor is proportional to mean Hubble parameter. The source of magnetic field is due to an electric current produced along z-axis. The role of bulk viscosity and magnetic field in establishing string phase of universe is presented. The physical and kinematical features of solutions are also discussed in detail.     

自旋为1的三粒子Heisenberg XXX链中杂质对热纠缠的影响

采用纠缠的度量方法Negativity研究了匀强磁场下自旋为1的含杂质三粒子Heisenberg XXX链的热纠缠特性.通过计算系统的杂质位与其余部分间的两体纠缠N_1-23及正常位与其余部分间的两体纠缠N_12-3,发现纠缠存在的临界温度T_c的改变来自杂质参数J₁的变化,随杂质参数J₁的增加而增加,外界磁场B< 关键词： 热纠缠 XXX链')" href="#">Heisenberg XXX链 杂质     

Ion beam induced atomic transport in bilayer systems

Atomic transport in ion beam mixed Co/Pt and Pd/Au bilayer systems have been studied from the shifts of maker layers in Rutherford backscattering spectroscopy. Thin layers (1 nm) of marker (Pd for Co/Pt and Ni for Pd/Au) were embedded as markers at each interfaces. 80 keV Ar⁺ was used to irradiate the marker samples at the temperature range between 90 and 600 K. The Co/Pt system shows isotropic atomic transport (J_Co/J_Pt∼1.1) at low temperatures and anisotropic atomic transport (J_Co/J_Pt∼5.0) at high temperatures. Meanwhile, the Pd/Au system shows near isotropic atomic transport (J_Pd/J_Au∼1.2) at all temperatures examined. These results were discussed in terms of the activation energies for the normal impurity diffusion, cohesive energy difference, and the vacancy migration energy. Atomic transport in thermal spike regime is closely related with the activation energy for normal impurity diffusion. In radiation enhanced diffusion regime, the cohesive energy and/or the vacancy migration energy plays a dominant role for the atomic transport.     

Thermal Entanglement in the Anisotropic Heisenberg XYZ Model with Different Dzyaloshinskii-Moriya Couplings

Thermal entanglement is investigated in a two-qubit Heisenberg XYZ system with different Dzyaloshinskii Moriya （DM） couplings. It is shown that different DM interaction parameters have different influences on the entanglement and the critical temperature. In addition, according to the relation between the real coupling coefficients Jx and Jz, a more efficient DM control parameter can be obtained by adjusting the direction of DM interaction.     

Quantum Discord Behavior for Two Qubits Heisenberg XYZ Chain with Inhomogeneous Magnetic Field

We report the quantum correlation behavior (quantum discord (QD)) of a two-qubit anisotropic Heisenberg XYZ chain under an inhomogeneous magnetic field. It is shown that in the lower region of b QD can be enhanced evidently through increasing anisotropic parameter γ, while the effects of γ are disappear when b is strong enough. The role of J _z is nearly opposite to γ, there is a critical value of b _c , with b>b _c QD is improved with decreasing interaction J _z , while the value of QD is nearly invariable whatever changing J _z when b<b _c . In addition, one can get non-zero QD by properly tuning J _z and γ even at a higher temperature. When inhomogeneity is increased to b _c , the QD can exhibit a regrowth procession, and the regrowth value of QD can be larger than that of before dropping in the region of weak J _z . We also obtain the ground state QD properties. These investigations can imply us more control parameters on quantum correlation in solid state systems.     

The anisotropic 3D Ising model

An expression for the free energy of an (001) oriented domain wall of the anisotropic 3D Ising model is derived. The order--disorder transition takes place when the domain wall free energy vanishes. In the anisotropic limit, where two of the three exchange energies (e.g. J_x and J_y ) are small compared to the third exchange energy (J_z ), the following asymptotically exact equation for the critical temperature is derived, sinh(2J_z /k _B T _c)sinh(2(J_x ?+?J_y )/k _B T _c))?=?1. This expression is in perfect agreement with a mathematically rigorous result (k _B T _c/J_z ?=?2[ln(J_z /(J_x ?+?J_y ))?ln(ln(J_z /(J_x ?+?J_y ))?+?O(1)]^?1) derived earlier by Weng, Griffiths and Fisher (Phys. Rev. 162, 475 (1967)) using an approach that relies on a refinement of the Peierls argument. The constant that was left undetermined in the Weng et al. result is estimated to vary from ～0.84 at ((H_x ?+?H_y )/H_z )?=?10^?2 to ～0.76 at ((H_x ?+?H_y )/H_z )?=?10^?20.     

Macroscopic quantum tunneling in small magnetic particles

Macroscopic quantum tunneling of magnetization in small antiferromagnetic clusters is studied for the spin-1/2 anisotropic (J _z ≡ J, J _x =J _y ≡J _xy ) Heisenberg model with the use of both perturbation theory and an exact numerical diagonalization technique. Splitting of the two lowest levels due to the lifting of the degeneracy between them (in the case J _xy =0) by the in-plane exchange (J _xy ≠ 0) is found to occur in the N/2th order of perturbation theory. Tunneling is absent in systems with an odd number of sites, in which the levels are doubly degenerate in zero magnetic field. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 9, 688–693 (10 May 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Spin waves in MnO; from 4°K to temperatures close to TN

Spin waves have been measured in MnO by inelastic scattering of neutrons from 4 °K to a temperature 0·25 °K below T_N. The 4 °K spectrum is interpreted in the frame of linear spin wave theory with effective exchange integrals J₁^? = 0·321 meV, J₁⁺ = 0·424 meV, J₂¹ = 0·446 meV and a phenomenological parameter for anisotropy D₁ = 0·059 meV. The effect of the actual dipole-dipole Hamiltonian is shown to give a priori a very good account of the lifting of the degeneracy of spin waves near the Brillouin zone center. The Bloch model for interacting spin waves and theories based on Green function approximations have been adapted to the MnO case, in order to compute the main properties (mean magnetization of a sublattice, anisotropic deformation, extra isotropic contraction and magnon spectrum) at many temperatures. Comparison of these with experimental results tends to favour a generalized Callen renormalization model, which gives an overall fit from 4 °K, to temperalures close to T_N.