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arXiv 1206.4501cond-mat.stat-mechphysics.comp-ph
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二维偶极相互作用伊辛模型中的条纹-四极相变:配分函数零点方法

Stripe-tetragonal phase transition in the 2D Ising model with dipole interactions: Partition-function zeros approach

Jacyana S. M. Fonseca, Leandro G. Rizzi, Nelson A. Alves

摘要:

我们进行了多重正则模拟来研究具有偶极相互作用的二维伊辛模型的临界行为。本文研究了在相互作用δ范围内的热力学相变,在此范围内观察到了宽度为h=1的条纹结构相。从局部更新算法获得的有争议的结果已被报道用于该区域,包括声称存在二阶相变线,该线在位于δ=0.85和1之间的某个地方的三临界点上方变为一阶。我们的分析依赖于从多规范模拟中获得的具有高统计数据的复杂配分函数零点。前导配分函数零点的有限尺寸标度关系产生临界指数ν,该临界指数明显与单个二阶相变线一致,从而排除了相图中该区域的三临界点。取向序参量的比热和磁化率的分析进一步支持了这一结论。

英文摘要:

We have performed multicanonical simulations to study the critical behavior of the two-dimensional Ising model with dipole interactions. This study concerns the thermodynamic phase transitions in the range of the interaction δwhere the phase characterized by striped configurations of width h=1 is observed. Controversial results obtained from local update algorithms have been reported for this region, including the claimed existence of a second-order phase transition line that becomes first order above a tricritical point located somewhere between δ=0.85 and 1. Our analysis relies on the complex partition function zeros obtained with high statistics from multicanonical simulations. Finite size scaling relations for the leading partition function zeros yield critical exponents νthat are clearly consistent with a single second-order phase transition line, thus excluding such tricritical point in that region of the phase diagram. This conclusion is further supported by analysis of the specific heat and susceptibility of the orientational order parameter.

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