共查询到20条相似文献,搜索用时 15 毫秒
1.
D. V. Dmitriev V. Ya. Krivnov A. A. Ovchinnikov A. Langari 《Journal of Experimental and Theoretical Physics》2002,95(3):538-549
The one-dimensional spin-1/2 XXZ model in a transverse magnetic field is studied. It is shown that the field induces a gap in the spectrum of the model with the easy-plane anisotropy. Using conformal invariance, the field dependence of the gap is found at small fields. The ground state phase diagram is obtained. It contains four phases with the long-range order of different types and a disordered phase. These phases are separated by critical lines, where the gap and the long-range order vanish. Using scaling estimates, the mean-field approach, and numerical calculations in the vicinity of all critical lines, we find the critical exponents of the gap and the long-range order. It is shown that the transition line between the ordered and disordered phases belongs to the universality class of the transverse Ising model. 相似文献
2.
The two-dimensional square lattice mixed-spin anisotropic Heisenberg ferromagnet with a transverse magnetic field is studied by means of the double-time Green's function. The analytic expressions of the critical temperature, the high-temperature zero-field susceptibilities, the spin-wave velocity, spin-wave stiffness and spin-wave gap are obtained. The phase diagrams in which the critical temperature, the reorientation temperature and the reorientation magnetic field are shown as a function of single-ion anisotropic parameter are discussed. 相似文献
3.
Thermal entanglement in two-qutrit spin-1 anisotropic Heisenberg model with inhomogeneous magnetic field 下载免费PDF全文
Erhan Albayrak 《中国物理 B》2010,19(9):90319-090319
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 Jx=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. 相似文献
4.
The effect of a zero-centered Gaussian random magnetic field distribution on the phase transition properties of the anisotropic quantum Heisenberg model has been investigated on a honeycomb lattice within the framework of effective field theory (EFT) for a two-spin cluster (which is abbreviated as EFT-2). Particular attention has been devoted to investigation of the effect of the anisotropy in the exchange interaction on a system with Gaussian random magnetic field distribution. The variation of the critical temperature with the randomness parameter (i.e., the width of the distribution) has been obtained for several anisotropy parameters. Critical Gaussian distribution width values, which make the critical temperature zero, have been obtained. Moreover, it has been concluded that all critical temperatures are of second order, and that reentrant behavior does not exist in the phase diagrams. 相似文献
5.
E. Albayrak 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(4):491-496
The thermal entanglement of a two-qubit anisotropic Heisenberg XXZ
chain with Dzyaloshinskii-Moriya (DM) interaction in an
inhomogeneous magnetic field was studied in detail. The effects of
the DM parameter, external magnetic field (B), a parameter b
which controls the inhomogeneity of B and the bilinear
interaction parameters Jx = Jy ≠ Jz (the anisotropic case) on
the concurrence (C) was formulated and studied in detail. The
behaviors of the concurrences for the cases between (J = Jz = 1) and
(J = -1,Jz = 1) and, (J = Jz = -1) and (J = 1,Jz = -1) at the ground
state and at the thermal equilibrium are exactly the same. It was
found that for the antiferromagnetic (AFM) case the entanglements
persist to higher temperatures in comparison with the ferromagnetic
(FM) case. In addition, the AFM case presents a special point at
which the nonzero concurrences are all equal at some special
temperatures. The further properties will be given in the text. 相似文献
6.
D. C. Li Z. L. Cao 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,50(2):207-214
We investigate the entanglement in a two-qubit Heisenberg XYZ
system with different Dzyaloshinskii-Moriya (DM) interaction and
inhomogeneous magnetic field. It is found that the control
parameters (Dx, Bx and bx) are remarkably different
with the common control parameters (Dz, Bz and bz)
in the entanglement and the critical temperature, and these
x-component parameters can increase the entanglement and the
critical temperature more efficiently. Furthermore, we show the
properties of these x-component parameters for the control of
entanglement. In the ground state, increasing Dx (spin-orbit
coupling parameter) can decrease the critical value bxc and
increase the entanglement in the revival region, and adjusting
some parameters (increasing bx and J, decreasing Bx
and Δ) can decrease the critical value Dxc to enlarge
the revival region. In the thermal state, increasing Dx can
increase the revival region and the entanglement in the revival
region (for T or bx), and enhance the critical value
Bxc to make the region of high entanglement larger. Also, the
entanglement and the revival region will increase with the
decrease of Bx (uniform magnetic field). In addition, small
bx (nonuniform magnetic field) has some similar properties to
Dx, and with the increase of bx the entanglement also
has a revival phenomenon, so that the entanglement can exist at
higher temperature for larger bx. 相似文献
7.
Quantum correlations in a two-qubit anisotropic Heisenberg XYZ chain with uniform magnetic field 下载免费PDF全文
Quantum correlations in an anisotropic Heisenberg XY Z chain is investigated by use of concurrence C and measurement-induced disturbance(MID). We show that the behaviors of the MID are remarkably different from the concurrence. Firstly, it is shown that there is a revival phenomenon in the concurrence but not in the MID, which is suitable for both the ground state case and the finite temperature case. Based on the analysis of the ground-state C and MID structures,we illustrate the reason why the ground-state MID does not show a revival phenomenon in detail. Then we explore different effects of the external and self parameters on entanglement and MID behaviors. It can be shown that the region of MID is evidently larger than the case of concurrence, and that the concurrence signals a quantum phase transition even at finite T while MID does not. Cases where the concurrence finally maintains one nonzero constant value regardless of the value of the variable B for a constant Jz, while MID decreases monotonously to zero with increasing B. We also show that if B can take a proper range of values, the concurrence decreases with the improvement of the anisotropic parameter γ, whereas an opposite effect for MID behaviors is presented. 相似文献
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10.
The variational approach based on the Bogoliubov inequality for the free energy is used to study the three-dimensional anisotropic Heisenberg XXZ model with a crystal field. The magnetization and the phase diagrams are obtained as a function of the parameters of the Hamiltonian. Limiting cases, such as isotropic Heisenberg, XY, and planar rotator models in two and three dimensions, are analyzed and compared to previous results obtained from analytical approximations as well as to those obtained from more reliable approaches such as series expansion and Monte Carlo simulations. A parametric procedure has been used in order to simplify the solutions of the self-consistent coupled equations. 相似文献
11.
12.
Znidarič M 《Physical review letters》2011,106(22):220601
We analytically and numerically study spin transport in a one-dimensional Heisenberg model in linear-response regime at infinite temperature. It is shown that as the anisotropy parameter Δ is varied spin transport changes from ballistic for Δ<1 to anomalous at the isotropic point Δ=1, to diffusive for finite Δ>1, ending up as a perfect isolator in the Ising limit of infinite Δ. Using perturbation theory for large Δ a quantitative prediction is made for the dependence of diffusion constant on Δ. 相似文献
13.
14.
Making the assumption that high-energy fermions exist in the two dimensional spin- 1/2 Heisenberg antiferromagnet, we present predictions based on the pi-flux ansatz for the dynamic structure factor when the antiferromagnet is subject to a uniform magnetic field. The main result is the presence of gapped excitations in a momentum region near (pi,pi) with energy lower than that at (pi,pi). This is qualitatively different from spin-wave theory predictions and may be tested by experiments or by quantum Monte Carlo. 相似文献
15.
The effects of multi-impurity on the entanglement of anisotropic Heisenberg ring XXZ under a homogeneous magnetic field are studied. The impurities make the equal pairwise entanglement in a ring compete with each other so that the pairwise entanglement exhibits oscillation. If the impurities are of larger couplings, both the critical temperature and pairwise entanglement can be improved. 相似文献
16.
An approximate expression is obtained for the dynamical susceptibility, χzz(q, ω), of the spin one half, simple cubic Ising model in a transverse magnetic field, which is appropriate to the disordered state (〈Sz〉 = 0). The susceptibility along the direction of the field is shown to contain a thermal part with a relative weight proportional to the difference between the isothermal and adiabatic susceptibilities and a width determined by the thermal diffusion constant. 相似文献
17.
Xiang Hao 《Physics letters. A》2008,372(7):1119-1122
Correct swap action can be realized via the control of the anisotropic Heisenberg interaction in solid-state quantum systems. The conditions of performing a swap are derived by the dynamics of arbitrary bipartite pure state. It is found that swap errors can be eliminated in the presence of symmetric anisotropy. In realistic quantum computers with unavoidable fluctuations, the gate fidelity of swap action is estimated. The scheme of quantum computation via the anisotropic Heisenberg interaction is implemented in a one-dimensional quantum dots. The slanting and static magnetic field can be used to adjust the anisotropy. 相似文献
18.
Da-Chuang Li 《Optics Communications》2009,282(6):1226-1636
Thermal entanglement is investigated in a two-qubit Heisenberg XYZ system with different inhomogeneous magnetic fields. It is found that different magnetic fields have different entanglement and critical values. In addition, according to the relation of spin-spin coupling coefficients, a more efficient control parameter of magnetic field can be obtained by adjusting the direction of external magnetic field. 相似文献
19.
Thermal entanglement in a mixed-spin Heisenberg XXZ model under a nonuniform external magnetic field
The thermal entanglement in (1/2,1) mixed-spin Heisenberg XXZ model is investigated under an external nonuniform magnetic
field. In the uniform magnetic field system, the critical magnetic field B
c and critical temperature T
c are increased by increasing the anisotropic parameter k. The degree of magnetic field b plays an important role in improving the critical temperature and enlarging the region of entanglement in the nonuniform
magnetic field system. 相似文献
20.
Lukyanova A.V. Rakhimov A.T. Suetin N.V. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1991,19(2):197-203
A numerical model of RF discharges in a steady transverse magnetic field is developed. This model is valid in a range of parameters (gas pressure, magnetic field, RF voltage) used in a number of experimental and technical installations. The comparison between numerical calculations and some experimental results is presented 相似文献