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arXiv 2104.05152cond-mat.stat-mechcond-mat.str-elhep-th
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三维$XY$模型中的异常对数表面相变

Extraordinary-log surface phase transition in the three-dimensional $XY$ model

Minghui Hu, Youjin Deng, Jian-Ping Lv

摘要:

普遍性是现代批评现象的支柱。标准情况是两点相关性随着距离$r$代数地减小为$g(r) \sim r^{2-d-η}$,其中$d$是空间维度,$η$是异常维度。最近,有人提出用对数普适性来描述O($N$)体系的异常表面跃迁。在这个对数普适性中,$g(r)$以对数距离的幂衰减为$g(r) \sim ({\rm ln}r)^{-\hatη}$,这与标准情况截然不同。我们通过Monte Carlo模拟探索了三维$XY$模型,并为对数普适性的出现提供了有力的证据。此外,我们提出的有限尺寸缩放的$g(r,L)$有两个距离的行为:同时包含一个大距离的高原,其高度衰减与$L$作为$g(L) \sim ({\rm ln}L)^{-\hatη'}$以及$r$依赖项$g(r) \sim ({\rm ln}r)^{-\hatη}$,与${\hatη'} \approx {\hatη}-1$。表征平台高度的临界指数$\hatη'$服从与螺旋度模量RG参数$α$的标度关系$\hatη'=(N-1)/(2πα)$。我们的图像也可以解释最近的海森堡系统的数值结果。对数普适性的进展极大地扩展了我们对临界普适性的理解。

英文摘要:

Universality is a pillar of modern critical phenomena. The standard scenario is that the two-point correlation algebraically decreases with the distance $r$ as $g(r) \sim r^{2-d-η}$, with $d$ the spatial dimension and $η$ the anomalous dimension. Very recently, a logarithmic universality was proposed to describe the extraordinary surface transition of O($N$) system. In this logarithmic universality, $g(r)$ decays in a power of logarithmic distance as $g(r) \sim ({\rm ln}r)^{-\hatη}$, dramatically different from the standard scenario. We explore the three-dimensional $XY$ model by Monte Carlo simulations, and provide strong evidence for the emergence of logarithmic universality. Moreover, we propose that the finite-size scaling of $g(r,L)$ has a two-distance behavior: simultaneously containing a large-distance plateau whose height decays logarithmically with $L$ as $g(L) \sim ({\rm ln}L)^{-\hatη'}$ as well as the $r$-dependent term $g(r) \sim ({\rm ln}r)^{-\hatη}$, with ${\hatη'} \approx {\hatη}-1$. The critical exponent $\hatη'$, characterizing the height of the plateau, obeys the scaling relation $\hatη'=(N-1)/(2πα)$ with the RG parameter $α$ of helicity modulus. Our picture can also explain the recent numerical results of a Heisenberg system. The advances on logarithmic universality significantly expand our understanding of critical universality.

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