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arXiv 1107.6022cond-mat.stat-mech
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均匀场中具有竞争相互作用的正方格子伊辛模型的标度行为

Scaling behavior of a square-lattice Ising model with competing interactions in a uniform field

S. L. A. de Queiroz

摘要:

利用转移矩阵方法,借助有限尺寸标度和共形不变性概念,研究了具有反铁磁第一和第二近邻相互作用的二维正方晶格Ising自旋1/2系统在均匀外场中的临界行为.在分离共线有序和顺磁相的临界曲线上,我们对共形异常$c$的估计非常接近于1,表明存在连续变化的指数。直接计算证实了这一点,这也支持了弱普适性的图像;然而,小但一致的偏离伊辛类值$η=1/4$,$γ/ν=7/4$,$β/ν=1/8$被发现。对于更高的字段,行移$(2 \times 2)$和无序相的线上,我们发现指数$η$的值非常接近零。

英文摘要:

Transfer-matrix methods, with the help of finite-size scaling and conformal invariance concepts, are used to investigate the critical behavior of two-dimensional square-lattice Ising spin-1/2 systems with first- and second-neighbor interactions, both antiferromagnetic, in a uniform external field. On the critical curve separating collinearly-ordered and paramagnetic phases, our estimates of the conformal anomaly $c$ are very close to unity, indicating the presence of continuously-varying exponents. This is confirmed by direct calculations, which also lend support to a weak-universality picture; however, small but consistent deviations from the Ising-like values $η=1/4$, $γ/ν=7/4$, $β/ν=1/8$ are found. For higher fields, on the line separating row-shifted $(2 \times 2)$ and disordered phases, we find values of the exponent $η$ very close to zero.

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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