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arXiv 0902.2938cond-mat.dis-nncond-mat.stat-mech
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T=0铁磁体到自旋玻璃转变时畴壁的标度行为

Scaling behavior of domain walls at the T=0 ferromagnet to spin-glass transition

O. Melchert, A. K. Hartmann

摘要:

本文研究了边长为L的正方形晶格上二维无规键Ising自旋系统中的畴壁激发,系统具有两种不同的连续无序分布。在这两种情况下,一个可调参数允许调整的无序,以便产生从自旋玻璃有序基态到铁磁基态的过渡。我们制定了一个辅助图论问题,其中域墙是由无向最短路径与可能的负距离。由于映射的细节,不能应用标准的最短路径算法。为了解决这样的最短路径问题,我们必须应用最小权完美匹配算法。我们首先确定了两种无序的铁磁-自旋玻璃转变的临界参数。当无序参数接近临界点时,我们研究了平均畴壁能量(~L^θ)和平均畴壁长度(~L^df)与系统尺寸的关系。对边长为L=512的系统进行有限尺寸标度分析,发现在自旋玻璃相中,两个指数都保持不变,即θ~- 0.28和df~-1.275。这与共形场论是一致的,其中似乎可以通过df-1=3/[4(3+θ)]将来自随机Loewner演化(SLE)分析的指数联系起来。最后,我们的特点转变的铁磁自旋形成的集群,因为一个收益从自旋玻璃有序铁磁基态。

英文摘要:

We study domain-wall excitations in two-dimensional random-bond Ising spin systems on a square lattice with side length L, subject to two different continuous disorder distributions. In both cases an adjustable parameter allows to tune the disorder so as to yield a transition from a spin-glass ordered ground state to a ferromagnetic groundstate. We formulate an auxiliary graph-theoretical problem in which domain walls are given by undirected shortest paths with possibly negative distances. Due to the details of the mapping, standard shortest-path algorithms cannot be applied. To solve such shortest-path problems we have to apply minimum-weight perfect-matching algorithms. We first locate the critical values of the disorder parameters, where the ferromagnet to spin-glass transition occurs for the two types of the disorder. For certain values of the disorder parameters close to the respective critical point, we investigate the system size dependence of the width of the the average domain-wall energy (~L^θ) and the average domain-wall length (~L^df). Performing a finite-size scaling analysis for systems with a side length up to L=512, we find that both exponents remain constant in the spin-glass phase, i.e. θ~- 0.28 and df~1.275. This is consistent with conformal field theory, where it seems to be possible to relate the exponents from the analysis of Stochastic Loewner evolutions (SLEs) via df-1=3/[4(3+θ)]. Finally, we characterize the transition in terms of ferromagnetic clusters of spins that form, as one proceeds from spin-glass ordered to ferromagnetic ground states.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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