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arXiv 1407.4189cond-mat.str-elcond-mat.stat-mech
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基于密度矩阵的相互作用系统有序性和关联性的数值方法

Density-matrix based numerical methods for discovering order and correlations in interacting systems

Christopher L. Henley, Hitesh J. Changlani

摘要:

我们回顾了最近介绍的无偏检测的序参量和/或主导的相关性的数值方法,在多体相互作用系统中,通过使用约化密度矩阵。大部分的文件是致力于“准简并密度矩阵“(QDDM),这是植根于安德森的观察,退化的破缺态有效的热力学极限,表现在有限的系统作为一组低能量的“准简并”状态(除了基态)。这种方法,其原始形式由于Furukawa等人。[Phys. Rev. Lett. 96,047211(2006)]给出了许多改进,首先是从二重对称破缺到任意情况的扩展。这是适用于两个测试情况下(1)相互作用的无自旋硬核玻色子的三角晶格和(2)自旋1/2反铁磁系统在逾渗阈值。此外,我们调查一种不同的方法称为“相关密度矩阵“,检测(可能是远程)相关性只从基态,但使用减少密度矩阵从一个集群组成的两个空间分离的区域。

英文摘要:

We review recently introduced numerical methods for the unbiased detection of the order parameter and/or dominant correlations, in many-body interacting systems, by using reduced density matrices. Most of the paper is devoted to the "quasi-degenerate density matrix" (QDDM) which is rooted in Anderson's observation that the degenerate symmetry-broken states valid in the thermodynamic limit, are manifested in finite systems as a set of low-energy "quasi-degenerate" states (in addition to the ground state). This method, its original form due to Furukawa et al.[Phys. Rev. Lett. 96, 047211 (2006)], is given a number of improvements here, above all the extension from two-fold symmetry breaking to arbitrary cases. This is applied to two test cases (1) interacting spinless hardcore bosons on the triangular lattice and (2) a spin-1/2 antiferromagnetic system at the percolation threshold. In addition, we survey a different method called the "correlation density matrix", which detects (possibly long-range) correlations only from the ground state, but using the reduced density matrix from a cluster consisting of two spatially separated regions.

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