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1.
The phase transitions of nearest-neighbour interacting Ising models on self-avoiding walk (SAW) chains on square and triangular lattices have been studied using Monte Carlo technique. To estimate the transition temperature (T
c) bounds, the average number of nearest-neighbours (Z
eff) of spins on SAWs have been determined using the computer simulation results, and the percolation thresholds (p
c) for site dilution on SAWs have been determined using Monte Carlo methods. We find, for SAWs on square and triangular lattices respectively,Z
eff=2.330 and 3.005 (which compare very well with our previous theoretically estimated values) andp
c=0.022±0.003 and 0.045±0.005. When put in Bethe-Peierls approximations, the above values ofZ
eff givekT
c/J<1.06 and 1.65 for Ising models on SAWs on square and triangular lattices respectively, while, using the semi-empirical relation connecting the Ising modelT
c's andp
c's for the same lattices, we findkT
c/J0.57 and 0.78 for the respective models. Using the computer simulation results for the shortest connecting path lengths in SAWs on both kinds of lattices, and integrating the spin correlations on them, we find the susceptibility exponent =1.024±0.007, for the model on SAWs on two dimensional lattices. 相似文献
2.
A.?N.?Kudasov 《Journal of Experimental and Theoretical Physics》2010,110(2):360-365
The Glauber dynamics of an Ising chain or ring is shown to be determined by two characteristic times: τ1 for relaxation of the average magnetization per spin and τ2 for dynamical spontaneous symmetry breaking. An analytical solution for magnetization dynamics in a finite chain with fixed spins at both ends is found by the method of images. This solution is then used to calculate the spin-spin correlation functions for rings and chains. At low temperatures, since τ1 ? τ2, there must exist a range of times when the chain is in one of two ordered states. 相似文献
3.
Fisher DS 《Physical review letters》1992,69(3):534-537
4.
M. A. Yurishchev 《Journal of Experimental and Theoretical Physics》2010,111(4):525-533
The behavior of Ising chains with the spin-spin interaction value λ in a transverse magnetic field of constant intensity (h = 1) is considered. For a chain of infinite length, exact analytical formulas are obtained for the second central moment
(dispersion) of the entropy operator Ŝ = -lnρ with reduced density matrix ρ, which corresponds to a semi-infinite part of the model chain occurring in the ground
state. In the vicinity of a critical point λc = 1, the entanglement entropy fluctuation ΔS (defined as the square root of dispersion) diverges as ΔS ∼ [ln(1/|1 − λ|)]1/2. For the known behavior of the entanglement entropy S, this divergence results in that the relative fluctuation δS = ΔS/S vanishes at the critical point, that is, a state with almost nonfluctuating entanglement is attained. 相似文献
5.
Z. Alexandrowicz 《Physics letters. A》1981,84(7):390-392
Ising critical clusters are related to the excess of neighbor spins of similar, over anti-similar, orientation. The clusters are approximately described by self-avoiding branching chains. γ, ν andalso a “time” (of growth from the origin) and a “perimeter/bulk” exponent are measured with the help of Monte-Carlo sampling. 相似文献
6.
We study the relaxation behaviour of the quantum Ising chain, focusing our attention onto the non-equilibrium dynamics of
the transverse magnetization.
The initial states, from which the magnetization relaxes, are product states
such as those generated by setting in contact several systems, each initially equilibrated at a given temperature.
Due to the free fermionic structure of the chain, the dynamics of the transverse magnetization is easily expressed in a compact
form. In the completely factorized initial state, corresponding to a situation where all the spins are thermalized independently,
we obtain in the scaling limit the Green function associated to the transverse magnetization.
The relaxation behaviour is also considered in the system-bath case, where part of the chain called the system is thermalized
at a temperature Ts and the remaining part is at a temperature Tb. The magnetization profiles show a scaling behaviour. Moreover, in the extreme case Tb=∞ and Ts=0, it is shown that the magnetization relaxes in quantized steps in the strong transverse field region. 相似文献
7.
《Nuclear Physics B》1999,538(3):731-758
Partition functions of one-dimensional Ising chains with specific long distance exchange between N spins are connected to the N-soliton τ-functions of the Korteweg-de Vries (KdV) and B-type Kadomtsev-Petviashvili (BKP) integrable equations. The condition of translational invariance of the spin lattice selects infinite-soliton solutions with soliton amplitudes forming a number of geometric progressions. The KdV equation generates a spin chain with exponentially decaying antiferromagnetic exchange. The BKP case is richer. It comprises both ferromagnets and anti ferromagnets and, as a special case, includes an exchange decaying as 1/(i − j)2 for large |i − j|. The corresponding partition functions are calculated exactly for a homogeneous magnetic field and some fixed values of the temperature. The connection between these Ising chains and random matrix models is considered as well. A short account of the basic ideas underlying the present work has been published in JETP Lett. 66 (1997) 789. 相似文献
8.
9.
G. Schröder T. Knetter M.J. Alava H. Rieger 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):101-105
Random walk arguments and exact numerical computations are used to study one-dimensional random field chains. The ground state
structure is described with absorbing and non-absorbing random walk excursions. At low temperatures, the local magnetization
follows the ground state except at regions where a local random field fluctuation makes thermal excitations easier. This is
explained by the random walk picture, implying that the magnetization lengthscale is a product of the domain size and the
thermal excitation scale.
Received 16 October 2000 and Received in final form 7 June 2001 相似文献
10.
Yin-Zhong Wu 《Optics Communications》2010,283(7):1569-1574
With the introduction of Dzyaloshinskii-Moriya (DM) interaction, dynamics of the remote entanglement in one-dimensional Ising chains is investigated. It is found that the DM interaction can excite the remote entanglement from an initial Néel state. For a given strength of DM interaction, the concurrence between the end spins oscillates and decreases simultaneously with the increase of the chain’s length, and drops to zero at a critical length. For the chains with two and three spins, it is very interesting that the dynamics of the staggered magnetization (or the chiral parameter) can be used to qualitatively estimate the evolution of the remote concurrence between the end spins. At last, we discuss the generation of W state from the Ising chain with DM interactions, and it is obtained that W state can only be prepared in the three-qubit and four-qubit chains with a specific strength of DM interaction. 相似文献
11.
This Letter deals with the problem of approximating the canonical state of an Ising spin chain by a hierarchical series of independent and identically distributed cluster states. Based on information geometry, it is shown that the structure of the effective Hamiltonian for each cluster state is inherited from the total Hamiltonian. This fact partly justifies the methodology of mean field theories. The issue of a phase transition is further analyzed from the point of view of statistical hypothesis testing. 相似文献
12.
Y. Z. Wu C. H. Shi X. Hao T. Pan X. F. Jiang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(2):253-257
The evolution of entanglement in a one-dimensional Ising chain with both two-body and three-body interactions, under two types
of initial states, is numerically simulated. We analyse three problems concerning the dynamics of pairwise entanglement: (i)
the possibility of generating large entanglement from an initial separable state by the use of a selective irradiation scheme;
(ii) the effect of three-body interaction on the generation of entanglement from an initial separable state; (iii) the effect
of three-body interaction on the decay of the entanglement from a state with only (m,n)-pair maximal entangled, and the rest
in product form. It is shown that a large pairwise concurrence Cmn can be obtained when the resonant, transverse radio-frequency fields are selectively switched on from the mth to nth spins.
Three-body interaction will decrease the oscillation amplitude of the nearest neighbour concurrence, while the oscillation
amplitude of remote pairwise concurrence will be greatly increased with the consideration of three-body interactions. For
an initial (m,n)-pair maximal entangled state, a slow decay of the pairwise concurrence Cmn is found with the introduction of three-body interactions. 相似文献
13.
14.
E. Solano-Carrillo 《Journal of magnetism and magnetic materials》2010,322(23):3760-1960
We investigate the physical processes which give rise to a multi-plateau ground-state magnetization curve in ferrimagnetic Ising chains with alternating spins (S,s) and different single-ion anisotropies on each sublattice of the system under an applied magnetic field, by using an elaboration of the molecular-field theory. Our analysis is started with the system () for which we use the transfer-matrix technique for comparison. In this system, we find a double-plateau structure (initial and saturation) in the magnetization curve for all values of , independent of anisotropies. Then we study two more elaborate systems, comparing the results with density-matrix renormalization group calculations, and finally generalize our argument to the general case. We find that for a specified range of the anisotropy parameters, the system exhibits 2s+1 plateaux, including the two classical and all those allowed for general quantum spin chains. This follows a similar rule as that known for spin-S(S≥1) Ising chains with single-ion anisotropy, for which 2S+1 plateaux appear in the ground-state magnetization curve, surviving even at low temperatures. 相似文献
15.
Metastability of Ising spin chains with nearest—neighbour and next—nearest—neighbour interactions in random fields
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One-dimensional Ising systems in random fields (RFs) are studied taking into account the nearest-neighbour and next-nearest-neighbour interactions. We investigate two distributions of RFs: binary and Gaussian distributions. We consider four cases of the exchange couplings: ferro-ferromagnetic (F-F), ferro-antiferromagnetic (F-AF), antiferro-ferromagnetic (AF-F) and antiferro-antiferromagnetic (AF-AF). The energy minima of chains of no more than 30 spins with periodic boundary conditions are analysed exactly. We found that the average number of energy minima grows exponentially with the number of spins in both cases of RFs. The energy distributions across the corresponding energy minima are shown. The effects of RFs on both the average and density of metastable states are explained. For a weak RF, the energy distributions display a multipartitioned structure. We also discuss the frustration effect due to RFs and exchange fields. Finally, the distributions of magnetization are calculated. The absolute value of magnetization averaged over all metastable states decreases logarithmically with the number of spins. 相似文献
16.
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
17.
18.
19.
Junction of three off-critical quantum Ising chains and two-channel Kondo effect in a superconductor
Domenico Giuliano Gabriele Campagnano Arturo Tagliacozzo 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(11):251
We show that a junction of three off-critical quantum Ising chains can be regarded as a quantum spin chain realization of the two-channel spin-1/2 overscreened Kondo effect with two superconducting leads. We prove that, as long as the Kondo temperature is larger than the superconducting gap, the equivalent Kondo model flows towards the two channel Kondo fixed point. We argue that our system provides the first controlled realization of two channel Kondo effect with superconducting leads. Besides its theoretical interest, this result is of importance for potential applications to a number of contexts, including the analysis of the quantum entanglement properties of a Kondo system. 相似文献
20.
Starting from the structure of the layered antiferroelectric squaric acid and assuming an ice rule type interaction mechanism of the protons it is shown that aboveT
c
the molecular layers may be considered as a system of parallel and orthogonal nearly independent linear Ising spin chains with strong intrachain and comparatively weak interchain interactions. Whereas the former are treated exactly as nearest neighbour interactions the interchain interactions are taken into account either by the molecular field approximation or, in computer simulations, by nearest neighbour interactions. The parameters of the model are related to the unusually small transition entropy, to the high and nearly temperature independent dielectric constant aboveT
c
,and to neutron scattering data. 相似文献