共查询到20条相似文献,搜索用时 140 毫秒
1.
采用格点自旋消约方法,将具有最近邻和次近邻耦合作用的镶嵌正方Ising晶格变换成等效的具有最近邻、次近邻和四体耦合作用的正方Ising晶格,得到系统近似解的临界点在K′C=0.4406868.结果表明:在相变点最近邻耦合作用K1和次近邻耦合作用K2之间满足一定关系.如果只计及镶嵌正方Ising晶格的最近邻耦合作用K1,则其严格解的临界点在K1C=0.7635.由此可以推断在正方格点间安放两个自旋的双镶嵌正方Ising晶格,在只计及最近邻耦合作用情况下,也是严格可解的. 相似文献
2.
利用等效变换和自旋重标相结合的方法, 研究了镶嵌正方晶格上的Gauss模型. 研究 发现, 该系统可以变换为正方晶格上具有最近邻和次近邻相互作用的Gauss系统, 由此严格求得了镶嵌正方晶格上Gauss模型的临界温度, 得到了该系统的精确相图. 相似文献
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本文用文献[4]中提出的方法,变S=1的Ising体系成一个粒子数不守恒的费密体系,严格地求得了具有最近邻及次近邻相互作用的反铁磁Ising晶格在任意外场下的基态能量,得到了零温的相图。
关键词: 相似文献
5.
简立方格子上Ising 自旋S(1)的反铁磁性——自由能的低温展式 总被引:1,自引:1,他引:0
本文采用文献[1]中的变换方法,将S=1的Ising体系变换成一个粒子数不守恒的Fer-mion体系.利用量子统计微扰理论,求得了具有近邻相互作用的反铁磁Ising晶格的自由能的低温展式,并由此求得它的低温磁化率. 相似文献
6.
采用等效变换的方法,把嵌套正方晶格转化为可求解的正方晶格.利用重整化群变换,我们求得了正方系统的临界点.结合本文中给出的两个变换关系,得到了嵌套正方晶格上反铁磁高斯模型的临界点为K*=-0.707b. 相似文献
7.
利用等效变换和重正化群变换的方法,在Sierpinskigasket晶格上研究了具有近邻和次近邻相互作用Gaussian模型的临界性质,求出了临界温度和关联长度临界指数.结果表明:在相变点近邻相互作用K1和次近邻相互作用K2之间满足一定的关系,这种关系对铁磁体和反铁磁体都适用.并且考虑次近邻相互作用后,临界温度和临界指数都不发生改变. 相似文献
8.
近年来,探索新的拓扑量子结构、深入分析各种多聚化拓扑晶格中的新奇物理性质已经成为热点.并且,多聚化拓扑模型在量子光学等领域的研究也愈发深入,拥有广阔的发展前景.本文聚焦于研究三聚化非厄密晶格中的新奇拓扑特性.首先,若晶胞内最近邻正反向耦合不相等,三聚化模型中的体态和边缘态出现趋肤效应.其中,随着最近邻耦合正反系数差的增大,拓扑保护的边缘态的宽度和简并度均可被调制,边缘态数量也会减少.其次,当在考虑次近邻耦合的影响时,随着次近邻耦合系数在适当范围内变化,系统本征能谱的上下能隙及其中具有趋肤效应的边缘态也会发生不对称的变化.此外,当适当改变两种耦合系数,三聚化非厄密模型的体态和边缘态的局域程度也会随之发生变化. 相似文献
9.
尹训昌 《原子与分子物理学报》2015,32(6)
采用等效变化的方法,把嵌套正方晶格转化为可求解的正方晶格。利用重整化群变换,我们求得了正方系统的临界点。结合本文中给出的两个变换关系,得到了嵌套正方晶格上反铁磁高斯模型的临界点为 K=-0.707b。 相似文献
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A decorated lattice is suggested and the Ising model on it with three kinds
of interactions K1,
K2, and
K3 is studied. Using an equivalent transformation, the square decorated Ising lattice is transformed into a regular square Ising lattice with nearest-neighbor, next-nearest-neighbor, and four-spin interactions, and the critical fixed point is found at
K1=0.5769,
K2=-0.0671, and
K3=0.3428, which determines the critical temperature of the system. It is also found that this system and
the regular square Ising lattice, and the eight-vertex model belong to the
same universality class. 相似文献
12.
The fully frustrated spin-1/2 Heisenberg FM/AF square bilayer in a magnetic field with the ferromagnetic inter-dimer interaction and the antiferromagnetic intra-dimer interaction is explored by the use of localized many-magnon approach, which allows to connect the original purely quantum Heisenberg spin model on a square bilayer with the effective ferromagnetic Ising model on a simple square lattice. Magnetization and specific heat are investigated exactly at a field-driven phase transition from the singlet-dimer phase towards the fully saturated ferromagnetic phase, which changes from a discontinuous phase transition to a continuous one at a certain critical temperature. The mapping correspondence between the spin-1/2 Heisenberg FM/AF square bilayer and the ferromagnetic Ising square lattice suggests for this special critical point of the spin-1/2 Heisenberg FM/AF square bilayer critical exponents from the standard two-dimensional Ising universality class. 相似文献
13.
A spin-1/2 and spin-3/2 mixed Ising system in a random field is studied by the use of effective-field theory with correlations. The phase diagrams and thermal behaviours of magnetizations are investigated numerically for the honeycomb lattice (z=3) and square lattice (z=4) respectively. The tricritical behaviours for both honeycomb and square lattices, as well as the reentrant behaviour for the square lattice are found. 相似文献
14.
《Physics letters. A》2019,383(21):2451-2455
The mixed spin-(1/2, 3/2) Ising model on a decorated square lattice, which takes into account lattice vibrations of the spin-3/2 decorating magnetic ions at a quantum-mechanical level under the assumption of a perfect lattice rigidity of the spin-1/2 nodal magnetic ions, is examined via an exact mapping correspondence with the effective spin-1/2 Ising model on a square lattice. Although the considered magnetic structure is in principle unfrustrated due to bipartite nature of a decorated square lattice, the model under investigation may display anomalous spin frustration driven by a magnetoelastic coupling. It turns out that the magnetoelastic coupling is a primary cause for existence of the frustrated antiferromagnetic phases, which exhibit a peculiar coexistence of antiferromagnetic long-range order of the nodal spins with a partial disorder of the decorating spins with possible reentrant critical behavior. Under certain conditions, the anomalous spin frustration caused by the magnetoelastic coupling is responsible for unprecedented absence of spontaneous long-range order in the mixed-spin Ising model composed from half-odd-integer spins only. 相似文献
15.
Monte Carlo study of the two dimensional quadratic ising ferromagnet with mixed spins ofS=1/2 andS=1
The single-spin-flip Metropolis algorithm is applied to an Ising ferromagnet with mixed spins ofS=1/2 andS=1 on the square lattice. The critical temperature obtained from our Monte Carlo simulation is very close to the high temperature series expansion result. The finite size scaling results for the exponents yield the two dimensional Ising values, which are in good agreement with those suggested by the universality hypothesis. 相似文献
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A simple real-space renormalization group method with two-terminal clusters is used to treat the critical behavior of Potts ferromagnet with free surface and defect plane on the same footing both for square and cubic lattices. For a square lattice, quite different critical behaviors are found for the cases of line defect and free surface. Whenq is larger than three, like the case ofa line type defect in ‘diamond’ hierarchical lattice, the order parameter on a defect line increases discontinuously at the bulk critical point if the defect interaction is sufficiently strong. This behavior, on the contrary, does not occur on the surface of a semi-infinite plane. For a cubic lattice, the phase diagram and renormalization group flow properties are obtained explicitly for bothq=1 (bond percolation) andq=2 (Ising model). In both cases, our calculations whow that the critical behavior on the surface of a semi-infinite system belongs to a different universality class from the critical behavior on the defect plane of a bulk system. 相似文献
18.
Lajko P Igloi F 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(1):147-152
We consider the two-dimensional (2D) random Ising model on a diagonal strip of the square lattice, where the bonds take two values, J1>J2, with equal probability. Using an iterative method, based on a successive application of the star-triangle transformation, we have determined at the bulk critical temperature the correlation length along the strip xi(L) for different widths of the strip L=21. The ratio of the two lengths xi(L)/L=A is found to approach the universal value A=2/pi for large L, independent of the dilution parameter J(1)/J(2). With our method we have demonstrated with high numerical precision, that the surface correlation function of the 2D dilute Ising model is self-averaging, in the critical point conformally covariant and the corresponding decay exponent is eta( ||)=1. 相似文献
19.
A relation between a class of stationary points of the energy landscape of continuous spin models on a lattice and the configurations of an Ising model defined on the same lattice suggests an approximate expression for the microcanonical density of states. Based on this approximation we conjecture that if a O(n) model with ferromagnetic interactions on a lattice has a phase transition, its critical energy density is equal to that of the n=1 case, i.e., an Ising system with the same interactions. The conjecture holds true in the case of long-range interactions. For nearest-neighbor interactions, numerical results are consistent with the conjecture for n=2 and n=3 in three dimensions. For n=2 in two dimensions (XY model) the conjecture yields a prediction for the critical energy of the Bere?inskij-Kosterlitz-Thouless transition, which would be equal to that of the two-dimensional Ising model. We discuss available numerical data in this respect. 相似文献
20.
The magnetic properties of bond-diluted nearest-neighbor interaction mixed spin-1/2 and spin-1 Ising ferrimagnetic spin system with different transverse fields are investigated within the framework of the finite cluster approximation (FCA). Particular emphasis is given to the square lattice with coordination number 2 = 4 for which magnetizations are obtained. The interactions Jij are assumed to be independent random variable with distribution P(Jij) = pδ(Jij-J) + (1-p)δ(Jij), where J < 0. If bond concentration p varies in the certain ranges, we find that the compensation temperature is obtained for the values of the different transverse fields Ω1/2 and Ω1 in a restricted region. We obtain the values of the critical different transverse fields and critical bond concentration in this paper. 相似文献