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arXiv 2005.10066cond-mat.stat-mech
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量子横场伊辛模型的蠕虫算法模拟

Worm-algorithm-type Simulation of Quantum Transverse-Field Ising Model

Chun-Jiong Huang, Longxiang Liu, Yi Jiang, Youjin Deng

摘要:

我们采用蠕虫算法模拟量子横场伊辛模型的路径积分表示,其中的扩展基是沿外场方向的自旋分量。在这样的表示中,配置可以被视为由成对相互作用的“扭结”和自旋下降(或自旋上升)的时间段构造的一组不相交的环。的缠绕概率为自旋下降的循环,一个无量纲的量表征环上的回路拓扑结构,观察到表现出小的有限尺寸的修正,并产生高精度的临界点在两个维度(2D)的$h_c \! =\! 3.044\, 330(6)$,显着改善现有的结果,几乎排除了最好的一个$h_c \! =\! 3.044\, 38 (2)$。在临界状态下,环的分形维数分别为$d_{\ell \downarrow} (1{\rm D}) \! = \! 1.37(1) \! \approx \! 11/8 $和$d_{\ell \downarrow} (2{\rm D}) \! = \! 1.75 (3)$,与经典的二维和三维O(1)环模型的分形维数一致.一个有趣的特征是,在一维(1D),自旋向下和向上的循环显示在整个无序相($ 0 \! \leq \! h \! < \! h_c$)的临界行为,具有分形维数$d_{\ell} \! = \! 1.750 (7)$,这是一致的壳尺寸$d_{\rm H} \! = \! 7/4$的临界2D渗滤集群。目前的蠕虫算法可以应用于模拟其他量子系统,如具有配对相互作用的硬核玻色子模型。

英文摘要:

We apply a worm algorithm to simulate the quantum transverse-field Ising model in a path-integral representation of which the expansion basis is taken as the spin component along the external-field direction. In such a representation, a configuration can be regarded as a set of non-intersecting loops constructed by "kinks" for pairwise interactions and spin-down (or -up) imaginary-time segments. The wrapping probability for spin-down loops, a dimensionless quantity characterizing the loop topology on a torus, is observed to exhibit small finite-size corrections and yields a high-precision critical point in two dimensions (2D) as $h_c \! =\! 3.044\, 330(6)$, significantly improving over the existing results and nearly excluding the best one $h_c \! =\! 3.044\, 38 (2)$. At criticality, the fractal dimensions of the loops are estimated as $d_{\ell \downarrow} (1{\rm D}) \! = \! 1.37(1) \! \approx \! 11/8 $ and $d_{\ell \downarrow} (2{\rm D}) \! = \! 1.75 (3)$, consistent with those for the classical 2D and 3D O(1) loop model, respectively. An interesting feature is that in one dimension (1D), both the spin-down and -up loops display the critical behavior in the whole disordered phase ($ 0 \! \leq \! h \! < \! h_c$), having a fractal dimension $d_{\ell} \! = \! 1.750 (7)$ that is consistent with the hull dimension $d_{\rm H} \! = \! 7/4$ for critical 2D percolation clusters. The current worm algorithm can be applied to simulate other quantum systems like hard-core boson models with pairing interactions.

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