共查询到20条相似文献,搜索用时 46 毫秒
1.
The entanglement in one-dimensional random XY spin systems where the impurities of exchange couplings and the external magnetic fields are considered as random variables is investigated by solving the different spin-spin correlation functions and the average magnetization per spin. The entanglement dynamics near particular locations of the system is also studied when the exchange couplings (or the external magnetic fields) satisfy three different distributions (the Gaussian distribution, double-Gaussian distribution, and bimodal distribution). We find that the entanglement can be controlled by varying the strength of external magnetic field and the distributions of impurities. Moreover, the entanglement of some nearest-neighbouring qubits can be increased for certain parameter values of the three different distributions. 相似文献
2.
The dynamics of the one-dimensional random transverse Ising model with both nearest-neighbor (NN) and next-nearest-neighbor (NNN) interactions is studied in the high-temperature limit by the method of recurrence relations. Both the time-dependent transverse correlation function and the corresponding spectral density are calculated for two typical disordered states. We find that for the case of bimodal disorder the dynamics of the system undergoes a crossover from a collective-mode behavior to a central-peak one and for the case of Gaussian disorder the dynamics is complex. For both cases, it is found that the central-peak behavior becomes more obvious and the collective-mode behavior becomes weaker as Ki increase, especially when Ki>Ji/2 (Ji and Ki are the exchange couplings of the NN and NNN interactions, respectively). However, the effects are small when the NNN interactions are weak (Ki<Ji/2). 相似文献
3.
Entanglement in One-Dimensional Random XY Spin Chain with Dzyaloshinskii--Moriya Interaction
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The impurities of exchange couplings, external magnetic fields and Dzyaloshinskii-Moriya (DM) interaction considered as Gaussian distribution, and the entanglement in one-dimensional random XY spin systems is investigated by the method of solving the different spin-spin correlation functions and the average magnetization per spin. The entanglement dynamics at central locations of ferromagnetic and antiferromagnetic chains have been studied by varying the three impurities and the strength of DM interaction. (i) For the ferromagnetic spin chain, the weak DM interaction can improve the amount of entanglement to a large value, and the impurities have the opposite effect on the entanglement below and above critical DM interaction. (ii) For the antiferromagnetic spin chain, DM interaction can enhance the entanglement to a steady value. Our results imply that DM interaction strength, the impurity and exchange couplings (or magnetic field) play competing roles in enhancing quantum entanglement. 相似文献
4.
利用递推关系方法在高温极限下研究了具有次近邻自旋耦合相互作用的一维随机量子Ising系统的动力学性质,求解了系统的自关联函数及谱密度.假设自旋耦合参量或横向磁场满足双高斯分布,研究发现当随机变量的标准偏差σJ(σB)较小时系统的动力学性质存在从集体模行为到中心峰值行为的交跨效应,当σJ(σB)较大时,交跨效应消失,系统只表现一种动力学行为.讨论了次近邻相互作用对系统动力学性质的影响,发现当KiJ2i(Ji和Ki分别为近邻和次近邻相互作用)时次近邻相互作用对系统动力学性质的影响不太明显,可以忽略;当Ki2Ji时,次近邻相互作用使得系统的中心峰值行为表现得更加明显,或使其集体模行为呈减弱的趋势. 相似文献
5.
A calculation is presented for the component magnetizations of an infinite multilayer Ising system, consisting periodically of two layers of spin-
A ions, two layers of spin-
B ions, and a disordered layer interface in between that is characterized by a random arrangement of A and B ions like a two-dimensional ApB1−p alloy. The system is a simple cubic Ising-type structure with a coordination number z = 6. The model is general for ferro- and for antiferromagnetic A-B exchange couplings. The A-A and B-B exchange couplings are regarded as ferromagnetic. An effective field theory that goes beyond mean field, is employed to calculate the bulk-like transition temperature, the different component magnetizations as well as the total bulk-like magnetization. The component magnetizations are calculated for different realistic model values of ferro- and antiferromagnetic A-B exchange constants, as a function of temperature and of the concentration parameter p that characterizes the disorder in the interface. We show that the presence of a disordered interface may significantly affect the component and total magnetizations. In particular, for the case of antiferromagnetic exchange couplings, it is shown that the system can acquire a compensation temperature for certain domains of values of the concentration parameter p in the disordered interface. 相似文献
6.
研究了一维随机量子XY自旋链中中心两量子位的纠缠特性,在该系统中引入了自旋间的交换耦合杂质、磁杂质和Dzyaloshinskii-Moriya相互作用,并且杂质满足高斯分布关系.通过数值计算,求出了自旋的关联函数和平均磁化强度,给出了Concurrence的解析表达式.结果表明:高斯分布和Dzyaloshinskii-Moriya相互作用对两量子位的纠缠有重要的影响,选择合适的交换耦合、外界磁场和Dzyaloshinskii-Moriya相互作用参数,可以控制和提高中心两量子位的纠缠.
关键词:
纠缠
XY模型')" href="#">随机量子XY模型
高斯分布
Dzyaloshinskii-Moriya相互作用 相似文献
7.
Boguslaw Zegarlinski 《Journal of statistical physics》1994,77(3-4):717-732
We consider a spin system on a lattice with finite-range, possibly unbounded random interactions. We show that for such systems the Glauber dynamics cannot decay to equilibrium exponentially fast inL
2 even at high temperatures. Additionally, for one-dimensional systems with unbounded random couplings we prove that with probability one the corresponding Glauber dynamics has a fast (subexponential) decay to equilibrium in the uniform norm, provided that the distribution of random couplings satisfies some exponential bound. 相似文献
8.
L. S. Lima A. S.T. Pires 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(3):335-342
In this paper we study the dynamics of the two-dimensional XY model with single-ion anisotropy, and spin S = 1, in the large
D phase, and low temperatures, using the bond operator formalism. The in-plane structure factor is a delta function. The out
of plane shows a three peak structure, which merges in a single peak at the Brillouin zone boundary. We analyze also spin
currents generated by a magnetic field gradient. The spin conductivity is calculated, at finite temperature, using the Kubo
formula. The model shows unconventional ballistic spin transport at finite temperature. The computed spin conductivity exhibits
a nonzero Drude weight at finite temperature. For ω< 2m, where m is the energy gap, the spin conductivity is described solely
by the Drude weight. There is a regular contribution to the spin conductivity for ω> 2m, which persist in the zero temperature
limit. The conductivity at the critical point, and for small frequencies, is (gμB)2/ħ times a universal scaling function of ħω/kB T. 相似文献
9.
Within the framework of the high-temperature series expansions technique, we examine the phase transition and the critical phenomena of a two-component superlattice with simple cubic structure, through three models: Ising, XY and Heisenberg. The reduced critical temperature of the system is studied as a function of the thickness of the constituents and the exchange interactions in each material, and within the interface. We show the existence of a critical thickness of the unit cell at which the reduced critical temperature of the binary superlattice remains insensitive to the exchange coupling within the interfaces. The values of the effective critical exponent γ eff associated with the magnetic susceptibility agreed with the universal classes in the limit cases where the superlattice is still comparable to an infinite simple cubic lattice. We attribute the breakdown in the universality hypothesis to the crossover effects. 相似文献
10.
W. Li Z. Zhang P. Tong 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(2):73
The effect of the Dzyaloshinskii-Moriya (DM) interaction on the heat conduction in the quantum Ising chain has been studied
by solving the Lindblad master equation. The chain is subject to a uniform transverse field h, while the exchange couplings {J
m
} between the nearest-neighbor spins are either uniform, random or quasi-periodic. The average energy-density profile and
the average energy current in the non-equilibrium steady state have been numerically calculated. The ballistic transport is
observed in the uniform Ising chain with DM interaction. For the random Ising chain with DM interaction, the energy gradient
is observed in the bulk of the spin chain whose energy current appears to scale as the system size ⟨Q⟩ ∼ exp(βN) with β < 0. For the quasi-periodic Ising chain with DM interaction, the J
m
takes the two values J
A
and J
B
arranged in the Fibonacci sequence. The energy gradient also exists in the spin chain and the energy current behaves as ⟨Q⟩ ∼ N
α
with α < 0. By increasing the strength of the DM interaction D, a non-trivial transition from the thermal insulator heat transport to anomalous heat conduction is found in the Fibonacci
Ising chain with large ratio of couplings λ = J
A
/J
B
. A rough phase diagram of λ vs. D is given in this paper as well. 相似文献
11.
We study the average density of states in a small metallic grain coupled to two superconductors with the phase difference
π, in a magnetic field. The spectrum of the low-energy excitations in the grain is described by the random matrix theory whose
symmetry depends on the magnetic field strength and coupling to the superconductors. In the limiting cases, a pure superconducting
symmetry class is realized. For intermediate magnetic fields or couplings to the superconductors, the system experiences a
crossover between different symmetry classes. With the help of the supersymmetric σ-model we derive the exact expressions
for the average density of states in the crossovers between the symmetry classes A-C and CI-C. 相似文献
12.
G. A. Petrakovskii K. A. Sablina A. M. Vorotynov O. A. Bayukov A. F. Bovina G. V. Bondarenko R. Szymczak M. Baran H. Szymczak 《Physics of the Solid State》1999,41(4):610-612
The temperature dependence of the magnetic susceptibility of Cu3B2O6 single crystals grown by spontaneous crystallization from a melt consisting of a mixture of CuO and B2O3 and the behavior of their magnetization are investigated in magnetic fields up to 55 kOe. A broad susceptibility maximum
is observed near 39 K, and a sharp drop in susceptibility is observed at T<10 K. The paramagnetic Néel temperatures for all orientations of the magnetic field in the crystal investigated are negative,
attesting to the predominantly antiferromagnetic character of the exchange interactions. The effective magnetic moment of
the Cu2+ ion is anisotropic and lies in the range from 1.054μ
B to 1.545μ
B. The magnetization depends linearly on magnetic field at T>10 K, whereas at temperatures below 10 K a discontinuity is observed at fields of the order of 40 kOe. At room temperature,
electron magnetic resonance characterized by an almost isotropic g factor (g=2.165) is detected at 36.22 GHz. The exchange interactions in Cu3B2O6 are analyzed on the basis of the Goodenough-Kanamori rules. The possibility of the establishment of a singlet magnetic state
in the crystal is analyzed.
Fiz. Tverd. Tela (St. Petersburg) 41, 677–679 (April 1999) 相似文献
13.
Ising models with nearest neighbor ferromagnetic random couplings on a square lattice with a (1, 1) surface are studied, using
Monte Carlo techniques and a star-triangle transformation method. In particular, the critical exponent of the surface magnetization
is found to be close to that of the perfect model, Β1
= 1/2. The crossover from surface to bulk critical properties is discussed. 相似文献
14.
A model of influence of non-heme Fe2+ ion on kinetics of electron transfer between quinone anion-radicals QA− and QB− in bacterial reaction centres is proposed and investigated. Physical mechanism of the influence is associated with singlet-triplet
transitions in QA−QB− Pair caused by interactions with paramagnetic Fe2+. The model incorporates exchange couplings between the particles and zero-field splittings in high-spin Fe2+. These interactions are shown to catalyze electron transfer in triplet pairs and alter the reaction yield significantly. 相似文献
15.
Using the boundary state formalism, we study a moving Dp-brane in a partially compact space-time in the presence of background fields: the Kalb-Ramond field B
μν, a U(1) gauge field A
α, and the tachyon field. The boundary state enables us to obtain the interaction amplitude of two branes with the above back-ground
fields. The branes are parallel or perpendicular to each other. Because of the presence of background fields, compactification
of some space-time directions, motion of the branes, and the arbitrariness of the dimensions of the branes, the system is
rather general. Due to the tachyon fields and velocities of the branes, the behavior of the interaction amplitude reveals
obvious differences from the conventional behavior. 相似文献
16.
We introduce a high-dimensional symplectic map, modeling a large system, to analyze the interplay between single-particle chaotic dynamics and particles interactions in thermodynamic systems. We study the initial growth of the Boltzmann entropy, SB, as a function of the coarse-graining resolution (the late stage of the evolution is trivial, as the system is subjected to no external drivings). We show that a characteristic scale emerges, and that the behavior of SB vs t, at variance with the Gibbs entropy, does not depend on the resolution, as far as it is finer than this scale. The interaction among particles is crucial to achieve this result, while the rate of entropy growth, in its early stage, depends essentially on the single-particle chaotic dynamics. It is possible to interpret the basic features of the dynamics in terms of a suitable Markov approximation. 相似文献
17.
18.
M. G. Tyazhlov A. I. Filin A. V. Larionov V. D. Kulakovskii D. R. Yakovlev A. Waag G. Landwehr 《Journal of Experimental and Theoretical Physics》1997,85(4):784-796
Spin relaxation of Mn ions in a Cd0.97Mn0.03Te/Cd0.75Mg0.25Te quantum well with photogenerated quasi-two-dimensional electron-hole plasma at liquid helium temperatures in an external
magnetic field has been investigated. Heating of Mn ions by photogenerated carriers due to spin and energy exchange between
the hot electron-hole plasma and Mn ions through direct sd-interaction between electron and Mn spins has been detected. This process has a short characteristic time of about 4 ns,
which leads to appreciable heating of the Mn spin subsystem in about 0.5 ns. Even under uniform excitation of a dense electron-hole
plasma, the Mn heating is spatially nonuniform, and leads to formation of spin domains in the quantum well magnetic subsystem.
The relaxation time of spin domains after pulsed excitation is measured to be about 70 ns. Energy relaxation of excitons in
the random exchange potential due to spin domains results from exciton diffusion in magnetic field B=14 T with a characteristic time of 1 to 4 ns. The relaxation time decreases with decreasing optical pump power, which indicates
smaller dimensions of spin domains. In weak magnetic fields (B=2 T) a slow down in the exciton diffusion to 15 ns has been detected. This slow down is due to exciton binding to neutral
donors (formation of bound excitons) and smaller spin domain amplitudes in low magnetic fields. The optically determined spin-lattice
relaxation time of Mn ions in a magnetic field of 14 T is 270±10 and 16±7 ns for Mn concentrations of 3% and 12%, respectively.
Zh. éksp. Teor. Fiz. 112, 1440–1463 (October 1997) 相似文献
19.
《Physics letters. [Part B]》1986,182(1):53-58
The new Yukawa couplings involving heavy matter E6 fields predicted in the framework of superstring theories are considered as a source of mass and magnetic moment for the neutrino. Given the experimental bound mve < 46 eV bounds are derived on the neutrino magnetic moment thus generated. Finally, a scenario is produced where the induced magnetic moment has the correct magnitude (∼10−11 μB) to explain an alleged depletion or solar neutrino flux during periods of maximum solar activity. 相似文献
20.
The phase diagrams of the transverse spin-1 Ising model with random interactions are investigated using a new technique in the effective field theory that employs a probability distribution within the framework of the single-site cluster theory based on the use of exact Ising spin identities. A model is adopted in which the nearest-neighbor exchange couplings are independent random variables distributed according to the law P(Jij)=pδ(Jij−J)+(1−p)δ(Jij−αJ). General formulae, applicable to lattices with coordination number N, are given. Numerical results are presented for a simple cubic lattice. The possible reentrant phenomenon displayed by the system due to the competitive effects between exchange interactions occurs for the appropriate range of the parameter α. 相似文献